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THE LIBRARY

THE UNIVERSITY
OF CALIFORNIA

LOS ANGELES

GIFT OF

H. L. LESSER

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SWITCHING EQUIPMENT

FOR

POWER CONTROL

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SWITCHING EQUIPMENT

FOR

POWER CONTROL

BY
STEPHEN Q. HAYES, A.B., E.E.

NSTITUTE ELECTRICAL ENGINEERS; SWITCHBOARD PROJECT ENGIN
WESTINGHOU8E ELECTRIC * MANUFACTURING CO.

FIRST EDITION
SECOND IMPRESSION

McGRAW-HILL BOOK COMPANY, INC.

NEW YORK: 370 SEVENTH AVENUE

LONDON: 6 & 8 BOUVERIE ST., E. C. 4

1921

PREFACE

Switching equipment for power control forms a very essential
part of any plant for the production or distribution of electrical
energy. This equipment has been aptly described as the " brain "
of the electrical system as it performs all of the duties of direction
and control that are so vital to the proper functioning of the
system.

Information on the subject of switchboards and switching
equipment can be found in very condensed form in certain
electrical handbooks, and specific data on definite appliances
can usually be obtained from manufacturers. Articles in the
technical press also furnish a certain amount of data on this
subject, but there has been no American book dealing with the
general subject.

Demand for a book on this subject has lead the author to
undertake its preparation basing it largely on his own articles
which had previously appeared in the switchgear and control
sections of the "Fenders Handbook for Electrical Engineers"
and in the Electric Journal, Electrical World, Southern Elec-
trician, Electrical Age, etc. These have been partly re-written
and brought up-to-date.

Manufacturer's publications have been consulted freely
and some of their descriptive matter utilized bodily or reworded
to adapt it to this book. The attempt has been made to select
such information as would be of the greatest use to the largest
number of readers and that would embody standard practice
rather than special applications.

Thanks of the author are due to various publishers for their

permission to utilize his material previously published, and to the

— o various electrical manufacturers for the data they furnished.

'_2 Grateful acknowledgment is also made to the author's many

j. friends and associates for information supplied and suggestions

as to subject matter and arrangements of material.

LU The main object of this book is to furnish the actual switch-

_j_ board operator the information that will help him to keep the

Mr> equipment in his care in the best operating condition, by ex-

0" plaining what should be expected of the apparatus and equip-

vi PREFACE

ment. It will also assist him in the selection and installing
of new material.

The secondary object is to help the student of electrical
engineering in a technical school to get a better understanding
of this branch of the art and to appreciate how the switching
equipment ties together the various generators, transformers,
feeders, etc., that make up the component parts of a generating
and distributing system.

Consulting engineers and others will find enough of the
theoretical features to give them an understanding of the func-
tions and limitations of the various devices. Such an under-
standing will facilitate specifying equipment that 'can be readily
obtained and that will operate satisfactorily under actual con-
ditions.

The arrangement of this book has been based on the idea of first
describing the switching apparatus, approximately in the order
in which the various devices were developed. This is followed
by considering the main connections desired in a power plant
and the means for carrying out the connections so as to obtain
the maximum amount of security and flexibility with the mini-
mum outlay. Switchboard panels, control desks, etc., are
considered next with the location of breakers, bus structures,
etc., and the general arrangement of the part of the power plant
devoted to switching equipment.

Description of apparatus has been confined almost exclusively
to present day standards to keep the subject matter down to a
reasonable length, but a few references have been made to some
of the older types of apparatus to show the progress of design.

American practice , forms the basis for the descriptions and
most of it is the practice of the largest electrical manufacturers.
The attempt has been made to include descriptions of apparatus
of other important builders, but it has been impossible to describe
all of the apparatus of all the builders. The data has been
obtained from various sources and the most readily available ma-
terial has been used.

STEPHEN Q. HAYES.

CONTENTS

PAGE
PREFACE V

I. SWITCHES 1

II. AUTOMATIC PROTECTION AND FUSES 24

III. CARBON BREAKERS 36

IV. OIL, CIRCUIT-BREAKERS 75

V. RELAYS 157

VI. SWITCHBOARD METERS 171

VII. INSTRUMENT TRANSFORMERS 198

VIII. LIGHTNING ARRESTERS 209

IX. REGULATORS 233

X. INDUSTRIAL CONTROL APPARATUS 254

XI. SWITCHBOARDS — GENERAL INFORMATION 267

XII. SMALL D. C. AND A. C. SWITCHBOARDS 296

XIII. LARGE HAND AND ELECTRICALLY OPERATED PANEL SWITCHBOARDS
FOR D. C. GENERATORS AND ROTARIES 321

XIV. HAND OPERATED A. C. SWITCHBOARDS 360

XV. Bus BARS AND WIRING GENERAL INFORMATION 381

XVI. BREAKER STRUCTURES 406

INDEX. . . 455

vii

SWITCHING EQUIPMENT
FOR POWER CONTROL

CHAPTER I
SWITCHES

KNIFE SWITCHES

Definition. — Switches may be considered as devices for
mechanically opening up an electric circuit and their design is
based primarily on the following features: They must, when
closed, carry their rated current without excessive drop or ex-
cessive heating and must take care of the overloads met in
practice; they must, while being opened, be designed to prevent
or render harmless any arcs that may be formed; they must,
when open, insulate all live parts for maximum potential in a
permanent manner.

Early Types. — The earliest types of switches consisted of
metal plates mounted on wooden blocks and connected together
by a plug inserted between them. The weakness of this first
design was the proximity of the plates and the tendency for an
arc to hold on when the plug was withdrawn. The next step
was to increase the distance between the two stationary contacts
and to use a movable plate attached to a handle for bridging the
gap between these stationary contacts. To avoid losing this
movable plate, the next step was to hinge it to one of the contacts
and from this beginning the present knife switches have been
developed.

Underwriters Rules. — The rules of the National Board of Fire
Underwriters relative to knife switches state: "All switches must
have ample metal for stiffness and to prevent rise in temperature
of any part of over 30 degrees Centigrade at full load, the con-
tacts being arranged so that a thoroughly good bearing at every
point is obtained with contact surfaces, advised for pure copper

SWITCHING EQUIPMENT FOR POWER CONTROL

blades, of about 1 square inch for each 75 amperes." As the
result of many tests the Underwriters settled on certain mini-
mum spacings between points of opposite polarity for various
currents and voltages of 250 D.C. or 500 A.C. and for 600
D.C. Most switches are designed to meet these requirements
as to temperature rise, contact surface, spacing and other
recommendations.

Multiple Blades. — Up to about 1200 amperes in capacity
knife switches are usually made with single blades, while for larger
capacity two or more blades per pole are supplied in order to
secure sufficient contact surface without making the blades and
jaws of abnormal width.

Quick Breaks. — "Auxiliary breaks" or "quick break attach-
ments" are furnished in many cases so as to make it impossible
to draw a dangerous arc by opening the switch slowly. These
quick break attachments are made in many forms.

Current-carrying parts of a well-designed switch consist of a
high grade of drawn copper of guaranteed conductivity. The
sectional areas and contact faces of all sliding and stationary
parts are calculated in accordance with the best practice, and a
liberal allowance is made for overloads.

Temperature. — The current-carrying parts adjacent to the
contacts will carry their full-rated current continuously with a
maximum temperature rise of either 20 or 30 degrees Centigrade
above the temperature of the surrounding atmosphere, depend-
ing on the class of service.

The rear connected switches of 1200-ampere capacity and larger
are given a lower rating for alternating current than for direct
current and are not guaranteed to carry more than their rated
current.

FIG. 1. — Typical knife switches.

Momentary Current. — The maximum momentary current
passing through knife switches should not be greater, owing to
mechanical and electrical limitations, than 50 times their normal
60-cycle 20-degree ampere rating. If the switches will be sub-

SWITCHES 3

jected to greater current momentarily than this, switches of
larger normal rating (amperes) should be used as they are both
mechanically and electrically stronger.

Front Connected. — Front connected knife switches are listed
by most makers up to 1200 amperes; for maximum voltages of
250 volts D.C. or A.C., 500 volts A.C., and 600 volts D.C. or
A.C.; with and without quick break blades; fused and unfused;
single and double throw.

Rear Connected with Round Studs. — These switches are
listed in capacities up to 1200 amperes not fused and 600 amperes
fused; for maximum voltages of 250 D.C. or A.C., 500 A.C. and
600 D.C. or A.C.; with and without quick break blades; single
and double throw.

Rear Connected with Laminated Studs. — These switches are
furnished with the conductor slots in the studs horizontal, or
vertical as required. They are listed in capacities from 1600
amperes to 6000 amperes for 250 volts D.C. and 500 volts A.C.,
and 600 volts D.C. and A.C. without fuses.

Handles. — Spade handles are regularly furnished on all 4-
pole switches and on all 3-pole above 600-amperes capacity;
they are also regularly furnished on single and 2-pole switches
with laminated studs. All other knife switches have straight
handles.

Fuses. — Fused switches are arranged for National Electrical
Code Standard enclosed fuses. All switches that are fused on
the hinge jaws have high jaws to allow the switch handles and
blades to lie fiat on the fuses. All switches that are fused on
break jaws have high break jaws to allow clearance between
handle and fuses.

Switch Studs. — The smaller capacity switches are made both
rear connected and front connected, while the larger switches
are almost invariably made rear connection. Up to approxi-
mately 1200 amperes the standard studs for rear connected
switches are circular and the switch studs are attached to their
bases by nuts screwed on these circular studs. Additional nuts
are provided for clamping strap connections or terminals. For
the larger capacity switches employed on low voltage boards,
strap connection are almost invariably used and to facilitate the
employment of the strap connections the switch studs are fre-
quently made laminated. A modification of the laminated
studs made with copper bars employs copper studs cast under

SWITCHING EQUIPMENT FOR POWER CONTROL

high pressure by means of which the conductivity of the cast
studs is approximately 90 per cent, that of rolled copper.
With the laminated stud switches the laminations can be ar-
ranged for the horizontal or vertical plane as is best adapted to
the wiring.

Knife Switches for A.C. Service.— Up to 800 amperes there
is no appreciable difference in the heating of knife switches on
direct current or alternating current. For larger capacities it is
found that for the same temperature rise it is necessary to derate
the larger knife switches for 60-cycle service. The constants
vary with different designs and different capacities. The 30-
degree rise is that covered by the Code while the 20-degree rise
is the one that is desirable for hot switchboard rooms.

Figure 1 shows the outlines of rear connected knife switches for
D.C. ratings up to 1200 amperes. The ratings given are based
on D.C. 30-degree rise and the same ratings are used on the
switches up to 800 amperes for 20 degrees and for 25- and 60-
cycle service. For the 1200-ampere size the 30-degree rating
for 25 or 60 cycles is 1100 amperes while for 20-degree rise the
rating is 1000 amperes for D.C. or A.C. With laminated studs
the ratings are as follows for the larger switches:

MAXIMUM AMPERES

30 Degree rating

20 Degree rating

A p

A.C.

D.C.

25 Cycles

60 Cycles

25 Cycles

60 Cycles

1600

1400

1200

1300

1200

1100

2000

1800

1600

1400

1200

3000

2600

2200

2400

2000

1800

4000

3400

2800

3200

2700

2200

6000

4200

3800

4500

3200

2800

Motor-starting Knife Switches. — Shown in Fig. 2 are used as
a simple and inexpensive method of starting synchronous con-
verters from the direct-current end and direct-current motors of
large capacity having starting conditions that will permit cutting
out the starting resistance in three steps. They are intended

SWITCHES 5

for starting conditions only, being rated in terms of the starting
current, and a short-circuiting line switch or circuit breaker
should be used to carry the running load. They will, however,
carry one-fourth their rated current continuously, so that the
short-circuiting line switch can be omitted where the full-load
current is only one-fourth of the starting current rating of
the switch.

FIG. 2. — Motor starting knife switch.

To start a motor the switch blade is thrown into the first jaw
and, after a moment's pause between steps, into each succeeding
jaw until the last is closed. The short-circuiting line switch,
where used, is then thrown in. The circuit should always be
opened by opening the line switch or circuit breaker.

These switches have four sets of contacts of such length that
the switch blade makes contact with each set in succession.
Each switch has four blades, a construction that allows of ample
ventilation and reduces the depth of the switch from the switch-
board.

To prevent large machines being started too quickly by throw-
ing the switch through all the positions without stopping on any
one position, a ratchet device is provided on the 1200, 2400, and
3600-ampere switches.

Field-discharge switches are used in the field circuits of
generators to serve as means of opening and closing the field
circuit. Just before the knife blades of the switch leave the

6 SWITCHING EQUIPMENT FOR POWER CONTROL

contact jaws, an auxiliary blade makes contact in such a way
tKat the discharge resistor is connected across the field winding,
thus allowing the inductive discharge of the field winding to die
out gradually .

Field -transfer switches are used for transferring the field cir-
cuits of synchronous converters or generators from one source
of excitation to another without opening the supply circuits,
where there is not likely to be a difference of potential between
the two sources. Where such a difference is likely to occur, a
transfer switch with additional jaws for inserting a limiting re-
sistor between the supply circuits should be used. They are
used especially where it is necessary to transfer a synchronous
converter or a generator field circuit from the bus bars to the
armature for self-excitation or to a direct-connected exciter as
with synchronous converters or synchronous motor-generator
sets started from the direct-current side.

The field-transfer switches are operated on the rocker principle
with their blades so shaped that just before one side leaves the
contact jaws the other makes contact with its jaws. Thus the
field circuit is not opened. The single-pole switches are used
particularly in railway service using grounded return.

The remote-control type has the switch mounted on a sub-base
in the rear of the panel and connected through levers to an oper-
ating handle mounted with a cover plate on the switchboard
panel. The operating handle has a latch, by means of which
the switch may be locked in the open or closed position at the
will of the operator.

The safety -first enclosed knife switch is used in steel mills, fac-
tories, mines, and similar places employing men having prac-
tically no knowledge of electricity and its attendant risks. The
danger to life and the employer's liability for death or injury to
a man touching a live part of the control switch or to a repair-
man inspecting a motor, have made an absolutely safe switch
almost a necessity.

The safety-first enclosed knife switch case contains an ordinary
single-throw knife switch with enclosed fuse holders at the hinged
end. These are mounted in an exceptionally strong iron box,
certain makes having a partition that separates the switch
blades from the fuse holders. The box is provided for conduit
connections. The upper or switch compartment can be opened
only by removing two machine screws, and padlocks when

SWITCHES 7

used; it is necessary to open this compartment only when
making connections and in case of inspection or repairs, as the
switch is opened and closed by an operating handle on the out-
side of the box, acting through a shaft and lever within. The
lower or fuse compartment contains the only parts that need be
handled — fuses to be replaced when blown out. The door of
this compartment is so interlocked with the switch that it
can be opened only when the switch is in the open position, and
with this door opened, the switch cannot be closed. Conse-
quently the fuses can be handled only when disconnected from
the live line. Due to the partition, it is impossible to reach the
live parts in the switch compartment. A spring is sometimes
provided to keep the door of this compartment closed. The
operating handle can be locked with the switch in the open
position, thus preventing tampering by unauthorized persons
and protecting repairmen working on the circuit.

PLUG SWITCHES

Plug switches were predecessors of the knife type of switch but
the ordinary plug type as first built did not have sufficient spac-
ing between contacts and could not be used to open the circuit
under load, and could not be built to carry more than 200 or 300
amperes at the most, so that the design of the knife type of
switch outstripped the plug. For certain classes of service,
however, the plug switch can be utilized to advantage. Various
types of plug switches have been developed by various manu-
facturers and at one time they were used to a considerable ex-
tent for A.C. service up to 200 amperes at 2400 volts in the form
of "plunger switches."

In the single-pole designs plug-type switches are still used to
a slight extent for arc lamp service and similar cases where a
high voltage switch of small current capacity rating is wanted.
These switches consist essentially of a tube of fibre or similar
material, with socket contacts at each end, mounted on the rear
of a panel, and a plug consisting of a metallic rod or tube with
an insulating handle. The plug when inserted through a hole
in the switchboard connects together the contacts at each end
of the tube.

Plug-type instrument switches are used for connecting a volt-
meter, ammeter, or power factor meter to any one of several

8 SWITCHING EQUIPMENT FOR POWER CONTROL

generators, and for making the multi-point connections required
when synchronizing generators.

For switchboard-voltmeter circuits the receptacles are made with
2, 4, 6, or 8 points. The metal parts are recessed in a bushing
of insulating material so as to avoid danger of accidental short
circuits. The separate sockets are spaced in such a way that
the plug cannot be inserted incorrectly, it thus being impossible
to short-circuit the line through the plug.

For Portable-voltmeter Circuits. — Receptacles and plugs are
used for connecting a portable voltmeter in parallel with the
switchboard voltmeter for the purpose of testing the accuracy of
the latter. A lamp cord running through the end of the handle
of the plug connects with the portable instruments, while the
receptacle is permanently wired up to the switchboard instrument.

For A.C. Ammeter Circuit. — Another type of plug is used for
testing the switchboard ammeter. It fits the same receptacle
and is identical with a transfer plug except that it has a lamp
cord which makes connection through the handle with the port-
able ammeter. This plug, when inserted in the receptacle, con-
nects the portable ammeter in series with the switchboard
ammeter, in the current transformer secondary circuit.

By the use of transfer plugs and receptacles, one ammeter can
be used to indicate the current in each phase. The primary of
a current transformer is connected in each phase of the circuit
and the secondary goes to the line terminals of its receptacle
where it is normally short-circuited. When the plug is inserted
in a receptacle the ammeter is connected in that circuit.

For ground detector circuits plugs and receptacles are used with
high potential push buttons, and a voltmeter or lamp to indi-
cate the existence of a ground on 1, 2, or 3-phase circuits. For
circuits of voltage over 125, switchboard transformers or the
necessary lamps in series are required.

Push-button switches are sometimes used for transformer type
ground detectors, engine-room signals and similar devices.
These are frequently arranged as the equivalent of double-throw
switches normally maintained in one position by a spring to
make one set of connections, and making other connections when
pushed in by hand or some of the switch gear mechanism.

For synchronizing circuits, plugs and receptacles (Fig. 3) are
used for making connections to synchronizing instruments.
Certain types have, in addition to the contacts for making the

SWITCHES 9

connections to the synchronizing instruments, a set of contacts
of 40-amperes capacity through which the control circuit of the
electrically operated generator circuit breaker may be connected
so that the generators can be thrown on the bus bars only when
the synchronizing instruments are in circuit.

FIG. 3. — Synchronizing plug and receptacle.

DRUM SWITCHES

Drum-type instrument switches are used for connecting one
instrument to any one of several circuits and for making the
multi-point connections required when synchronizing generators.

Construction. — Ruggedness and compactness are salient fea-
tures of the best instrument switches in a typical design. Mov-
able contact members, securely mounted on a substantial bake-
lite-micarta drum, engage with stamped contact fingers as the
drum is rotated to the right or left. The switching element is
housed in a substantial bakelite-micarta tube. A segment of
the housing is easily removable for inspection and adjustment.

The operating key is of black moulded material with a polished
black finish; the dial-plate markings are polished copper, on the
raised parts, with a black-mat background; and the housing is
finished in dull black.

All of these instrument switches, with the exception of the
ammeter and thermocouple switches, have removable keys or
handles. These keys are labeled and so constructed that they
cannot be inserted in the wrong switches.

Ammeter switch is so made that with one ammeter, one am-
meter switch and two or more current transformers on a poly-
phase circuit, the ammeter can be connected so as to read the
current in any phase. Switching contacts are so arranged that
the current transformer secondary circuits are never opened.
For connections see Fig. 4.

Thermocouple switch is built so that with one switch per gen-
erator, the potentiometer or temperature indicator can be con-

10 SWITCHING EQUIPMENT FOR POWER CONTROL

2 Phase tmmeto Snitch 3 Phase tmneter Switch

fir- 1 1mpendent Cir-

famefer Switch cult tin ' meter Switch

*/«/

Onim Detelipment
Offftoitiea

FIG. 4. — Ammeter switch connections.

Circuit Diagrams

821 321

Fio. 5. — Wattmeter switch connections.

SWITCHES

nected so as to read the temperature in any couple or search
coil on any machine.

Voltmeter switch is so made that with one voltmeter switch
for each polyphase circuit, one voltmeter and, for service above
600 volts, the necessary potential transformers, the voltmeter
can be connected to read the voltage on any phase of any circuit.
One key is required for each voltmeter and its group of switches.
If more than one group of voltmeter and switches is desired,
each group can be supplied with a different key arrangement.

Frequency-meter switch is arranged so that with one frequency
meter the necessary potential transformers and one switch for
each bus system, the frequency can be read on any bus system.
One key is required for each frequency meter.

Wattmeter, watt-hour meter, power-factor meter and reactive-
factor meter switches are made so that with one instrument, one
switch with proper labeling and key arrangement for each single
or polyphase circuit, and the necessary instrument transformers,
readings can be taken on any circuit. One key is required for
each instrument. For connections see Fig. 5.

TTp,"Tl"

Note This ttjle of iirltch

provided with two

marked

Ing which will throw the

twitch onlj the

Koto; For iTnohronlxIng with lamps onlj omit :

and Insert Individual lamps on paneli at points marked x

and add one lamp on rear of board u ihown bj dotted UDM

FIG. 6. — Connections for synchronizing between machines.

Synchronizing switch for synchronizing between machines is so
made that with one synchronoscope equipment, one switch for
each machine, and the necessary potential transformers, a syn-
chronizing indication can be obtained between any two machines.
One running key and one incoming key are required. The run-

12 SWITCHING EQUIPMENT FOR POWER CONTROL

ning key is to be placed in the synchronizing switch of one of
the machines running and can be turned to the running position
only; the incoming key is to be placed in the synchronizing
switch of the machine being brought in and can be turned to
the incoming position only. Each switch has a running and an
incoming position. For connections see Fig. 6.

Synchronizing switch for synchronizing between machine and
bus is so made that with one synchronoscope equipment, one
switch for each generator on a single-bus system and two switches
for each generator on a double-bus system and the necessary
potential transformers, a synchronizing indication between the
bus and any incoming machine can be obtained. One key only
for each board is required. Synchronizing switches are built
with and without interlock contacts for the closing circuit of
electrically operated circuit breakers. For connections see
Fig. 7.

Clrcuit Diagram,

For Electrlodlj
Operate Breaker,

«« i.?M>w BfcrV Puc M«*-Opr.Bkn.or Eta,
Opr.Bte.Wlthou.tater.ock

blDEle Handle Bjn.

8w.»« Etac Opr.Bkrs.

Poshfclu

and bus .Ire I with oonnectiuLS
tkereto Is not required.
When lamps orjj are provided bus
win I trill, connections thereto

FroinUcn. } From (

FIG. 7. — Connections for synchronizing to bus.

CONTROL SWITCHES

Control switches of different types have been developed for
the control of electrically operated devices of various kinds, put
into service, and then superseded by later devices.

The first control devices were small single-pole, double-throw
knife switches, usually made with a spring to return the blade to
the open position after being thrown one way or the other. A
modification of this switch had a little celluloid plunger located
in an enlargement of the blade, colored red on one end, green

SWITCHES

on the other, and of slightly greater length than the depth of
the blade. The color of the end that was projecting from the
blade showed the last position to which the switch had been
thrown.

The disadvantage of this type of control switch was the possi-
bility of its being accidentally operated by the station attendant
when reaching for another device, and the trouble arising from
the live contacts on the face of a switchboard where there were
no other live parts on the front.

G. E. Control Switch. — A push button for closing a control
circuit and another for tripping was an early scheme adopted to
do away with the live contacts on the front. The push button
had the disadvantage of being liable to accidental closing by the

FIG. 8. — General Electric Co. pull button switch.

switchboard operator so a "pull button" was substituted for a
push button and the twin pull button shown in Fig. 8 has been
standardized by the General Electric Company for control
devices on switchboards.

By using pull buttons in place of push buttons there is little
likelihood of the attendant operating the device unintentionally
when cleaning or working about the switchboard. Red and
green indicating lamps with prismatic lenses are used for signals
and a little target, colored red and green and located between the
buttons, shows the last movement that has been made, so that if
the target shows one color and the indicating lamp another the
breaker has tripped automatically.

14 SWITCHING EQUIPMENT FOR POWER CONTROL

Lewis and Roth combination control switch and indicating
device put on switchboards made by them embodies the essential
features of no live parts on the front of the board, a position
indicator with red and green target, the usual red and green
indicating lamps, a spring return to the off position, great
compactness, and good appearance when worked into a miniature
bus arrangement.

Westinghouse Control Switch. — The Westinghouse Electric
& Manufacturing Company first tried pull-button switches but
soon shifted over to a drum-control switch that possessed many
features that it was difficult to embody in a pull-button device.
By varying the drum development and the number of contact
fingers, various interlocks could be made and one control switch
could handle the three electrically operated breakers for motor
starting, the forward and reverse motion with limit switches
for governors, valves, rheostats, etc.

Their latest control switch is built along modern and latest
practice in controller design, having an insulated square shaft
for carrying the moving contact segments with special view to
securing space economy while having due regard for proper
insulation, as shown in Fig. 9.

FIG. 9. — Westinghouse drum control switch.

These control switches have been designed for the control of
circuits governing the operation of solenoid operated switches
and circuit breakers or their control relays, solenoid operated
rheostats, motor operated rheostats, motor operated engine
and turbine governors, and motor operated feeder-potential
regulators.

The adaptability of the control switch to a variety of special
requirements insures a neat and uniform appearance of equipment
on the front of the switchboard. As an aid in selection for the
switchboard operator, control switches for circuit breakers are

SWITCHES 15

provided with handles of a different shape than those of the
other control switches.

These control switches will successfully handle current values
of considerable magnitude. However, where the current de-
mands, of closing solenoids in particular, are in excess of certain
values, a control relay should be interposed between the controller
contacts and the solenoid. In general, control relays are not
usually required in the trip-coil circuit of breakers.

Construction. — Ruggedness and compactness are salient fea-
tures of control switches. Advantage has been taken in their
design of the years of successful operation and experience on
railway controller contacts. Rugged stamped contact fingers
of the same type as employed on railway controllers are used;
the advantages of the horn-gap construction inherent in this
design are well known. Movable contact members mounted on
a square insulated shaft engage with stationary spring-contact
fingers as the shaft is rotated to the right or left. The switching
element is housed in a substantial bakelite-micarta tube, which
provides a simple rigid insulating structure. A segment of the
housing is easily removable for inspection and adjustment.

Space Requirements. — The switches with their indicating
lamps can be mounted 3^ inches between vertical center lines
and 7 inches between horizontal center lines, or 7 inches between
vertical center lines and 3)-^ inches between horizontal center
lines. This feature is in keeping with modern requirements of
space economy for switchboards.

Telltale. — All control switches are provided with a mechani-
cal indicating device that shows the last manual operation of the
control switch. When the handle is released, the switch auto-
matically returns to the neutral (central) position.

Lamp Cut-out. — Several designs of switches for the control of
solenoid operated breakers, embodying a signal lamp cut-out
are made. The oval handle on these switches may be turned
past the trip position to a lamp cut-out position which is 90
degrees from the neutral (central) position and there latched in
place; this, therefore, closes the circuit to trip the breaker, and
then opens both the trip circuit and the indicating lamp circuit
with the breaker " locked " in the open position. On double-bus or
relay-bus systems, this permits cutting out all breakers and lamps
on the bus not used; the horizontal position of the control handles
when set this way is very readily observed by the operator.

16 SWITCHING EQUIPMENT FOR POWER CONTROL

Lamp indicators are connected in the control circuit of elec-
trically operated circuit breakers to indicate whether the breaker
is open or closed.

Operation. — The lamps are usually so connected with the signal
switch on the breaker that when the breaker is closed the red
indicator will be lighted and when the breaker is open the green
indicator is lighted. On one style of the control switch, an
additional indicator is so connected to the signal and control
switches that when the breaker is tripped automatically this
indicator is lighted and remains lit until the control switch
turns to the "close" or "open" position; this is the equivalent
of the mechanical indicating device that is self-contained on
certain control switches.

FIG. 10. — Lamp indicator.

Construction. — Each indicator, shown on Fig. 10, consists of
a receptacle projecting through the switchboard for holding
a candelabra lamp, and a lens holder with a special prismatic
lens. The lamp is removable from the front of the panel and
the receptacle is provided with a glass-tube fuse at the back
of the board. The lens holder is pushed into the end of the
receptacle from the front of the board and is held firmly by spring
clips. A special feature of the lens is the prismatic projection
extending across its face which makes the indications visible
from any position in front of the board.

These indicators are arranged for mounting on 2-inch panels,
but can be used on l^-inch and 13^-inch boards by the addition
of an adapter.

A 125 or 140-volt candelabra screw-base lamp should be used.
For control voltages over 140, the 140-volt lamp should be used
with suitable resistor.

Control Relays. — Control relays are interposed between the
contacts of a main relay or the contacts of a control switch and
the apparatus to be controlled, when the current required to

SWITCHES 17

operate the apparatus exceeds the current-carrying or interrupt-
ing capacity of the main relay or control switch contacts.

Control relays are thus frequently required for the closing-coil
circuits of electrically operated carbon and oil circuit breakers.
In general, the tripping-coil circuits of circuit breakers do not
require sufficient current to make necessary the use of control
relays.

Operation. — The operating coil for the control relay is connec-
ted directly across the control circuit by the closing of the control
switch, causing the control relay to close, connecting the circuit-
breaker closing coil across the line.

Control relays are given a maximum current and voltage
rating based on intermittent operation. They will give satis-
factory service for intermittent duty, namely, with power im-
pressed thereon for not more than 10 seconds out of every 60;
this is the condition found under usual operating requirements.

Construction. — These control relays are an adaptation of the
well known "contactor type" of switch used most extensively
for industrial motor control.

The contacts, which have ample overload capacity, are
pressed firmly together with a self-cleaning action.

Flexible copper shunts carry the current from the moving
contact to the lower terminal of the relay. No current passes
through pins, springs, or bearing surfaces. The top contact is
stationary and, therefore, requires no shunt.

Blowout coils are used on all switches. The blowout coils
and arcing horns are very efficient in operation, the blowout
coils being of special design to handle the highly inductive control
circuit. The arc is distributed over a relatively large area as
soon as formed and is quickly extinguished. Hence it has
practically no destructive action.

DISCONNECTING SWITCHES

Knife-type disconnecting switches are used for isolating oil
circuit breakers, feeders, etc., or for making various connections
that do not have to be opened under load.

In American practice the knife switches for 2500 volts or less
are usually mounted directly on a base of soapstone, marble or
similar material, while for higher voltages, insulators of various
kinds are used to support the switch jaws. Up to 2500 volts
these disconnecting switches are made either front connection,

SWITCHING EQUIPMENT FOR POWER CONTROL

FIG.

11. — Heavy duty disconnecting
switch.

or rear connection, or both, while for higher voltages than 25,000
they are almost invariably made front connection only.

For light service, switches with petticoat insulators are em-
ployed, these being made for
inverted mounting or for
vertical mounting.

For heavy duty, Fig. 11
shows a 4000-ampere, 15,000-
volt disconnecting switch.
This type is built in capacities
of 400 up to 4000 amperes at
7500 and 15,000 volts, and up
to 600 amperes for higher
voltages up to and including
73,000. In this switch a
corrugated conical pillar type
insulator is used with the
switch part attached to the
top of the insulator and the
bottom of the insulator at-
tached to a metal base in

such a manner that, if an insulator proves defective, it can
readily be replaced without the necessity of replacing the bal-
ance of the switch. Owing to the severe mechanical stresses
set up at the instant of short circuit on systems of large
capacity, latches are
provided on these dis-
connecting switches to
prevent them being
blown open.

For voltages of 73,000
and above, it is cus-
tomary to employ dis-
connecting switches like
Fig. 12, mounted on
porcelain posts of the
built-up type employing
a sufficient number of

sections or units to secure the voltage test desired, either for
indoor or for outdoor service.

With this type of switch, if an insulator becomes damaged or

FIG. 12. — Disconnecting switch with built up
insulator column.

SWITCHES

defective, the units can be readily unbolted from the built-up
pillar and replaced by a new section.

Fig. 13 shows a series of switches made for voltages from
22,000 to 110,000. These are mounted on corrugated pillar type
insulators that are given a dry test of three times normal voltage.
On the larger sizes a truss blade is furnished to secure rigid con-
struction and safety catches are supplied to prevent the switches
jarring open. The caps holding the jaw blades are clamped to
a wall or other flat structure after they are removed from the
wooden template on which the switches are shipped.

The Delta-Star Electric Company have the blades of their
disconnecting switches made either plain, for normal light ser-
vice, or with latches of various types where the short-circuit

FIG. 13. — Line of General Electric Co. disconnecting switches.

current is such that there is a possibility of the magnetic stress-
es blowing the switch open if it were not provided with latches.

A very compact type of disconnecting switch for attaching
to a bus bar is shown in Fig. 14. In place of cable terminal at
the hinge jaw of switch, provision can be made for copper strap
connection.

All of the disconnecting switches previously described
have been single pole and are operated by means of a hook stick.
The various companies make modifications for multipole service
mechanically operated as shown in Fig. 15 this being a Delta-
Star, three-pole double-throw distant-control switch. Any
combination, front or rear connected, can be supplied.

Outdoor high voltage disconnecting switches of one design are
built with each pole mounted on three insulators, the end ones

20 SWITCHING EQUIPMENT FOR POWER CONTROL

carrying break jaws and the line connectors being stationary,
the middle one carrying the switch blade rotating in such a way
as to introduce a double break into the line.

FIG. 14. FIG. 15.

FIG. 14. — Delta-Star bus-bar switch.

FIG. 15» — Outdoor high voltage 3 P. D. T. distant control disconnecting
switch.

HORN -BREAK SWITCHES

Where it is necessary to open up a high tension outdoor line
with power on or when supplying the charging current for a long
transmission line, it is necessary to provide arcing horns for the
switches, if oil breakers are not employed. These horn-break
switches have been made by various builders.

Fig. 16 shows a 50-K.V. horn-gap switch made in single-pole
units but arranged so that any number of poles can be mechanic-
ally interconnected by means of an adjustable bar and operated
from a single operating handle. The main contacts are protected
from all burning by the auxiliary arcing horns which make con-
tact before the main contact is closed, and which break away
after the main contact is opened. The main contact itself is
completely covered by a sleet hood and protected from burning
by the auxiliary arcing horn.

SWITCHES

FIG. 16. — R. & I. E. Co. horn-gap switch 50-K.V. single break.

END VIEW

Fia. 17. — Horn-gap switch 70-K.V. double break.

22 SWITCHING EQUIPMENT FOR POWER CONTROL

For 70-K.V. service these switches as shown in Fig. 17 are
made double break in order to obtain the proper gaps in the line.
These switches are intended primarily for mounting on a pole
top or a structure with the insulators in the vertical position
and the switch arm swinging around on a horizontal plane.

FIG. 18.— R. & I. E. Co. horn-gap switch 120-K.V. vertical break.

For still higher voltages a switch of the type shown in Fig. 18
is utilized. This switch is designed for 120-K.V. service, and
while the porcelain pillars are mounted in a vertical position, the
switch arm is so arranged as to swing open in a vertical plane
instead of a horizontal one.

Where it is desired to obtain automatic protection for a sub-
station or sectionalizing of a line at a moderate cost, an automatic
attachment can be added to these horn-gap switches.

The insulator which carries the solenoid trip is mounted in a
bearing, and is capable of rotation through a small angle under
the torsion of a spring. The trip coil is energized by the main

SWITCHES 23

line current. On overload, the plunger in the trip coil magnet
releases the latch allowing the insulator to swing by force of the
spring. This motion moves a trip rod which releases a main
latch, allowing the 3 poles of the switch to open simultaneously.
The switch automatically resets by bringing the operating handle
to the open position. The switch cannot be held closed on an
overload, or on a short circuit.

Modification of this series trip mechanism can be applied to
the double-break or the vertical-break horn-type switch.

CHAPTER II

AUTOMATIC PROTECTION AND FUSES
GENERAL FEATURES

One of the most important features of switch gear is the
automatic protection secured by means of fuses, circuit breakers
or similar devices which guard the various circuits against the
trouble that may arise from overloads or any other condition
apt to cause damage.

A constant potential generator tends to maintain its voltage
independent of the amount of current it may be developing.
With a B.C. generator, unless this current is limited by some
automatic device, the excessive current is very apt to damage the
armature and particularly the commutator, so automatic pro-
tection is usually furnished to prevent the current in a D.C.
generator reaching a value apt to damage it.

Exciter and Field Circuits. — It has become standard practice,
however, not to supply automatic protection, such as fuses or
circuit breakers, in exciter and field circuits, as the sudden open-
ing of the field circuits of the A.C. generators, due to the operation
of a fuse or breaker in the field or exciter circuit, might cause
far greater damage due to puncturing the insulation of the A.C.
generator than would arise from the overloading or even short-
circuiting of an exciter. In some cases fuses are furnished in
exciter circuits of two or three times the normal capacity of the
machine so that no ordinary overload could cause them to blow
while a certain amount of protection will be afforded to the exciter
against a dead short circuit.

Where the exciters also supply current for station service
automatic protection is sometimes supplied that will cut off the
station circuits in case of trouble while leaving the exciter con-
nected to the field bus. Where exciters are used in parallel
with a battery and in certain other conditions, reverse-current
circuit breakers are supplied in the exciter circuit that will open
only when the exciter tends to draw power from the bus bars
instead of delivering power to them.

AUTOMATIC PROTECTION AND FUSES 25

A.C. Generators. — With the exception of some generator panels
where fuses or breakers are furnished for the protection of a line
fed directly from the machine or of feeders run from the A.C.
bus bars without other protection, it is customary to omit any
fuses, circuit breakers, or other automatic devices in the armature
circuits of the A.C. generators as most machines have sufficient
armature reaction to enable them to stand short circuits for a
short time without damage to themselves. In other words, no
protection is needed for a moderate size A.C. generator with
fairly high armature reaction.

With some very large machines of low armature reaction or
important installations it is sometimes advisable to use a circuit
breaker in the generator circuit with a reverse-current time limit
relay, but such cases are usually special and form an exception to
the general rule.

Differential Protection. — More recently a scheme of differential
protection for large generators has become almost universal,
utilizing current transformers in each end of each phase winding
of a generator, i.e., at the neutral as well as in the outgoing leads
and balancing these against each other. For all conditions of
overload or external short circuit the system is non-automatic,
but any internal short circuit or ground in the generator will
cause an unbalancing in the relay circuit causing the tripping of
the generator breaker and field switch.

Converters. — For the protection of synchronous converters
or motor-generator sets, the rules applied to D.C. generators
apply for the direct-current end of the machine. The circuit
breaker, which is almost invariably used in the D.C. circuit, is
usually provided with a low voltage release coil in addition to
the usual overload coil, and this release coil may be short-
circuited by a reverse-current relay if it is desired to guard against
the machine taking in D.C. current and delivering A.C. current.
The speed limit device, when furnished, usually short-circuits
this low voltage release coil to cut off the D.C. current in case
of excessive speed.

For the A.C. end of a converter fed directly from a low tension
generator or bus, automatic protection is usually furnished.
When fed from its own transformer or bank of transformers, the
automatic protection is usually supplied on the high tension side
of the transformers and no automatic devices are used between
the A.C. end of the converter and the low tension transformer
circuit.

26 SWITCHING EQUIPMENT FOR POWER CONTROL

Circuit Protection. — In a generating station with A.C. genera-
tors supplying power to a low tension bus, which in turn fur-
nishes current to step up transformers feeding a high tension bus
and outgoing transmission lines, it is customary as previously
explained to make the generator breakers non-automatic. Those
for the low tension side of the transformers are made overload
automatic, those for the high tension side of the transformers
non-automatic, those for the outgoing lines automatic and any
tie or junction breakers in the bus bars non-automatic. In a
step down transformer station the same scheme is followed
except that the high tension transformer breaker is automatic
and the low tension non-automatic. Occasionally with trans-
formers differential relay devices are used, operated from current
transformers in the high tension and low tension circuit in such
a manner that as long as the ratio of transformation remained
practically constant, the breakers would be non-automatic but
if any internal trouble in the transformer modified this ratio of
transformation, the differential relay would act and both high
tension and low tension breakers would be tripped out.

FUSES

Fuses, open link, at first were small copper wires and their
great drawback was the high melting point of the copper and
the consequent heat of the molten metal dropping from the
fuse and the formation of copper globules. To reduce the
heat of the molten metal, lead, tin, or some alloy with low fusing
point was used, but such fuses had the drawback of being too soft
and easily damaged when tightening up the contact nuts. The
next step was to use alloy fuses with copper tips and these are
still used to some extent.

As the price of aluminum was reduced this material was used
largely for fuses as it has a high conductivity reducing the
amount of metal fused, a fairly low melting point and almost
complete vaporization of the metal fused. By using wide strips
of aluminum cut to form two or more bridges, fairly reliable open
fuses can be made up to 1200 amperes. An ordinary metal
strip exposed to draughts of various kinds is apt to be very erratic
in its behavior as a fuse and is apt to throw molten metal when it
blows. These defects in the behavior of open fuses finally
led to various devices to remedy these troubles — one being the
enclosure of the fuse in a suitable receptacle or tube.

AUTOMATIC PROTECTION AND FUSES

FIG.

19. — Typical expulsion fuse and
block.

Fuses, Expulsion. — It was found that the fuses for 1100-and
2200-volt service were decidedly dangerous unless properly
covered up, and if they were placed in an airtight box they were
apt to rupture the box by the explosion of the gases formed when
the fuses blew. It, therefore, became necessary to provide a vent
for the gases and the natural development was to place the vent
in such a position that the gases in expanding caused a strong
draught through the vent and
this was used for blowing out
the arc. This resulted in the
expulsion type of fuse holders.

The earliest designs of this
type comprised a removable
fuse holder of lignum vitae
or similar tough close-grained
wood, equipped with termi-
nals which fit into suitable
blocks. Later types have the fuse placed in a fibre tube and
arranged to blow out through one end like a bomb.

Fig. 19 shows a typical expulsion type fuse block for indoor
service" up to 7500 volts in capacities up to 100 amperes and simi-
lar fuse holders are available up to 25,000 volts.

These fuse blocks are made especially for opening the circuit
in the event of sudden and severe overloads or short circuits,
but they are also entirely suitable for the protection of circuits
in the case of gradually increasing overloads if the fuse wire is
inserted in asbestos sleeving.

The fuse tube is readily removable from the contact clips
and the fuse wire easily inserted therein, making the re-fusing
a very simple matter. These fuse blocks will operate satisfactor-
ily on any circuits within their interrupting capacity, which is
approximately 1000 amperes at 7500 volts when used one per
wire and proportionately greater or less at other lower or higher
voltages.

The fuse tube is hollow and one end is left open, so that when
the fuse blows, the metallic vapors are expelled from the tube
through the open end and successfully extinguish any arc inci-
dent to the blowing of the fuse. Before being inserted in the fuse
tube the fuse wire should be enclosed in asbestos sleeving. The
asbestos sleeving prevents the gradual charring of the inside of
the fuse tube by the overheated fuse and thereby eventually

28 SWITCHING EQUIPMENT FOR POWER CONTROL

lengthens the life or prevents burning out of the fuse tube. The
open end of the fuse tube extends beyond the contact jaw so that
all danger of the expelled vapors coming in contact with the
metallic portion of the block is eliminated.

Enclosed fuse consists essentially of a fusible wire, strip or
sets of wires and strips enclosed within a tube, usually of fibre,
filled with a material to exclude the air and to facilitate the
opening of the circuit when the fuse blows by absorbing the gases
formed and chilling out the arc. Suitable terminals are provided
so that the fuse may be mounted in a fuse block.

N.E.C. Fuses. — When enclosed fuses were first put on the
market each manufacturer developed his own designs of terminals
and used his own spacings so that there was no uniformity

D IPO

FIG. 20. — Enclosed fuse with ferrule FIG. 21. — Enclosed fuse with blade

contacts. contacts.

and the fuse of one make could not be used in the fuse holder of
another manufacturer. To avoid this confusion the representa-
tives of the fuse builders and the National Board of Fire Under-
writers finally adopted certain standard dimensions and types
of contacts for various sizes and voltages. Up to 60 amperes
ferrule type contacts are used as shown in Fig. 20, and from 61
amperes to 600, knife blade contacts are employed as shown in
Fig. 21. One set of dimensions are used for fuses up to 250 volts
and another for fuses up to 600 volts. Fuses that correspond
to the accepted dimensions and that meet other requirements
agreed on are known as National Electrical Code (N.E.C.)
fuses and are perfectly interchangeable.

Limits. — On large systems the circuit characteristics should be
such as to limit the maximum overload power passing through
the fuse to approximately 10,000 kilo volt-amperes. Circuit
breakers are recommended instead of enclosed fuses where the
rated capacity of the generators supplying the circuit on which
they are directly installed exceeds 2000 kilovolt-amperes, as fuses
are not suitable for such circuits.

Indicators. — Each fuse is provided with a simple but reliable
device which indicates whether the fuse has blown or is still

AUTOMATIC PROTECTION AND FUSES 29

intact. This indicator is in plain view so that the condition of
the fuse can be determined at a glance.

Fuse blocks and fuse holders for enclosed cartridge fuses for
voltages up to 25,000, front and rear connected, are used for
mounting on the wall or on switchboard panels and are rated
according to the ampere and voltage capacities of standard
cartridge fuses with which they are designed to be used, and the
ratings apply to either direct or alternating current.

The 250-volt and 600-volt fuse blocks have the National Elec-
trical Code standard dimensions and will receive any cartridge
fuses of corresponding ampere capacities conforming thereto.

Fuse blocks for glass cartridge fuses for capacities up to
2 amperes, 250 volts, single, two and three-pole use a small
glass-tube fuse of 2-amperes capacity. They are used princi-
pally for the protection of instruments connected directly to the
line without transformers and in the secondary circuit of in-
strument transformers.

The complete block consists of fuse clips of the ferrule type
mounted on porcelain blocks with barriers on the outside edges
and, with the two and three-pole blocks, between poles. They
are made for mounting on the wall or in
the rear of panels and are front connected.

Switchboard-type fuse blocks as shown in
Fig. 22 are made for switchboard use
where it is desired to replace the fuse
from the front of the panel. The standard
enclosed fuse is inserted in the clip in the
plug and the plug is then screwed into the
receptacle until the fuse enters the inner contacts. These fuse
blocks are for 1^-inch, 1^-inch and 2-inch panels.

Fuse blocks with porcelain insulators and cast-iron or sheet-
steel bases, wall mounting type, are used for the protection of
switchboard mounting and other voltage transformers of small
capacity for voltages up to 25,000 maximum. They can, how-
ever, be used on any circuit up to their rated capacity.

Transformer Fuses. — When the A.C. system was developed
with distributing transformers mounted on houses or poles and
exposed to the weather, it became necessary to develop suitable
fuse protection for them and various types of fuse blocks and
fuse holders were designed. The usual form for moderate
capacity transformers on 7500-volt circuits was a porcelain fuse

SWITCHING EQUIPMENT FOR POWER CONTROL

holder carrying a small piece of fuse wire placed in deeply re-
cessed grooves in the fuse holder but as voltages increased, it
became necessary to go to another type.

Fig. 23 shows a 25,000-volt combination fuse holder and dis-
connecting switch developed for outdoor service and this fuse
holder, of the expulsion type, can readily be made suitable for
higher voltages by using larger insulators and increasing the
dimensions of the fuse tube.

FIG. 23. — Disconnecting switch type of expulsion fuse.

S. & C. Fuse. — Another type of fuse, known as "The S. & C.
Fuse" but sometimes called "Carbon Tetrachloride Fuse" has
been developed by Schweitzer & Conrad, Inc. These have been
used outdoors and indoors for voltages up to 115,000 and in
current capacities up to 400 amperes. The fuse is located in a
glass tube that contains a spiral spring, the lower end of which is
connected to the bottom ferrule. The upper end of the spring
connects to the fuse wire passing through a cork, the upper end
of the fuse wire being connected to a short wire soldered to the
cap on the top ferrule. At the top of the spiral spring and just
below the cork is a funnel-shaped liquid director. The glass tube
is filled with a noninflammable liquid of extremely high dielectric

AUTOMATIC PROTECTION AND FUSES

strength, having none of the objectionable characteristics of oil.
This liquid is not only not an oil, and therefore noninflammable,
but is one of the most effective fire extinguishing liquids known.

Operation. — The melting of the fuse wire releases the spiral
spring which contracts instantaneously, drawing the fuse wire
down towards the bottom of the tube and thus introducing a very
large gap. Simultaneously with the introduction of this gap, the
liquid extinguishes the arc and interrupts the current flow, the
rapidity of its action being accelerated by the liquid director which
is drawn down with the spring and so forces the liquid directly
on to the moving terminal.

Since the dielectric strength of the liquid is about 250,000 volts
per inch, the gap between the top ferrule and the top end of the
submerged spring gives an enormous
factor of safety. The dimensions of
the glass tube and other parts vary,
depending upon the ampere capacity
and voltage rating of the fuse. Ac-
cording to tests, this fuse operated in
less than one-fifth of the time required
by oil circuit -breakers; the longest
time required to open the circuit was
0.03 seconds. This is remarkable
when compared to the quickest oper-
ating oil circuit breaker which takes
at least 4 cycles on 25-cycle current,
or a minimum of 0.16 seconds.

Weatherproof Cut-out. — For use as
a weatherproof primary cut-out, a
special holder of moulded insulating
material is provided. The S. & C.
Fuse attached to a handle of the same
material as the holder, fits into the
holder in such a manner as to make
a bayonet type plug switch.

Fused Switch. — The fused switch is furnished for those installa-
tions where it is desired to install a combination disconnecting
switch and fuse mounting, but where the space is so limited that
the regular types cannot be used.

The middle portion of the disconnecting blade is replaced by
two pieces of Bakelized insulating material, and the fuse is

Fro. 24. — Schweitzer-Conrad
shunted switch with carbon
tetra-chloride fuse.

SWITCHING EQUIPMENT FOR POWER CONTROL

mounted across this insulated gap so that the current is carried
through the fuse. The fuse is mounted in regular fuse clips
with the regular retaining bales, so that no difficulty is en-
countered in the opening and closing of the blade.

Shunted Switch (Fig. 24) . — Another adaptation of this type of
fuse consists essentially of a disconnect shunted by a fuse of low
amperage and provided with a lock, so that the disconnect
cannot be opened unless the fuse is
in place. If the disconnect is opened
when it is carrying current, the cur-
rent is shunted through the fuse where
it is interrupted when the fuse blows
due to the current being above the
rated current of the fuse.

Mountings. — A number of types of
mountings for S. & C. fuses have
been developed by Schweitzer &
Conrad, Inc. and the Delta-Star
Electric Company. Various types
are furnished for both indoor and
outdoor service, including many
combinations for installing the fuses
with choke coils, disconnecting
switches, etc. For outdoor service,
the fuse is mounted on a pair of
petticoat insulators mounted hori-
zontally, vertically, or at an angle of
45 degrees. Similar outdoor arrange-
ments, utilizing General Electric Ex-
pulsion Fuses are shown in Fig. 25.
The fuse holder for expulsion type
fuses is made of porcelain, designed to
give high mechanical strength. At
each end are placed contact elements,
which engage the stationary contacts
of the mounting. The upper end is
closed, the lower end open.

The fuse wire is passed through the holder and connected to the
brass contacts at both ends. At the upper or closed end of the
holder, the fuse cross-section is reduced insuring that the fuse
melts at this point. Melting of the fuse generates gas, which

FIG. 25. — Delta-Star outdoor
fuse arrangement.

AUTOMATIC PROTECTION AND FUSES 33

expands and explosively forces the arc downward, expelling it
through the lower or open end of the holder, thus rupturing the
circuit.

Fused Breaker. — The fused type circuit breaker is a modifica-
tion of the carbon circuit breaker that has been used to quite a
large extent in connection with moderate capacity high voltage
circuits.

This circuit breaker is designed for potentials from 6000 to
60,000 volts. The circuit breaker consists of two hardwood
poles, one being longer than the other, mounted upon porcelain
petticoat insulators, to which are secured the terminals for the
main leads or wires. The wood poles are connected by a hinge,
so that their extremities are in line at the upper end. On the
upper end of each pole is mounted a copper sleeve supporting
a round carbon contact block with a hole through its center.
The longer pole is provided with spring jaws or clips so that it
may be quickly and easily attached to, or detached from, the
terminals on the insulators. The short pole has a flexible wire
running through its interior; this wire is connected to the copper
sleeve at the upper end of the short pole and to the lower clip
terminal on the long pole. The sleeve at the upper end of the
long pole is connected to the upper clip terminal. These connec-
tions make the sleeves at the upper ends of the two poles the
terminals of the apparatus.

Early Type. — In the earliest type of fused circuit breaker the
fuse of aluminum wire was exposed in the air and it was neces-
sary to allow ample space above it for the arc to rise and dissipate
itself. For the lower voltages the marble base was depended
on for insulation while for the higher voltages the marble base
was mounted on insulators. These fused switches were used in
considerable number in some of the earlier Interurban Railway
Substations filling the demand for a moderate priced high voltage
overload breaker to give automatic protection on the high ten-
sion side of the transformers.

Latest Type. — The latest modification of this device as shown
in Fig. 26 has the marble base replaced by petticoat insulators
mounted on long pins.

Construction. — The fused type circuit breaker is lightly, yet
strongly constructed. The circuit breaker mechanism consists
of a long hardwood pole on which is mounted a movable arm con-
sisting of a reinforced fuse tube. At the bottom of the fuse tube

34 SWITCHING EQUIPMENT FOR POWER CONTROL

FIG. 26. — Fused circuit breaker.

is a brass expulsion chamber which is connected to the lower ter-
minal of the breaker by a flexible copper shunt. Attached to

the top of the pole and
forming the upper cir-
cuit-breaker terminal
there is a brass bracket,
with a groove along its
top, which supports the
fuse, and a wing nut to
hold the end of the fuse
when the breaker is
closed. The fuse passes
from the wing nut over
the bracket and down
through the fuse tube
to the expulsion chamber

where it is attached to the screw-plug terminal shown in the end

of the expulsion chamber.
S. & C. Breaker.— Still another

type of high voltage breaker

based on the same principles as

the S. & C. Fuse is made by

Schweitzer & Conrad, Inc. and

is shown in section in Fig. 27.
Construction. — T he s wi t c h

consists essentially of a moving

contact mounted on the end of

a spring actuated operating rod,

and of a stationary contact

mounted in the base of the circuit

breaker, and so arranged that

when the moving contact reaches

the closed position, the two con-
tacts engage each other. The

current is conveyed to the

moving contact through flexible

copper connections so that the

current carried by the spring

is negligible. Mounted on the

end of the operating rod and next to the moving contact

is the liquid director, a funnel-shaped arrangement that forces

Flexible

Cable

FRONT VIEW OF
ilHCUIT C.REAKER
IN CLOSED
POSITION Beplaceable
Contacts

FlG

27. — S. & C. high voltage
breaker.

AUTOMATIC PROTECTION AND FUSES 35

a powerful stream of the liquid onto the moving contact as it
recedes through the liquid when opening. Immediately under
the stationary contact is the excess pressure vent which opens
when the pressure in the main tube becomes abnormally high,
due to the rupturing of very heavy short circuits. This vent, as
well as the two contacts, is very easily replaced.

Latching Arrangement. — The operating rod which carries the
moving contact extends through the top of the circuit breaker
and is provided with a cross-bar to which the operating ropes or
other mechanism are attached. On top of the switch is a latching
arrangement which holds the circuit breaker in the closed posi-
tion. This latch is released by a small lever projecting to the
front which makes it convenient for any method of tripping
that may be chosen.

Overload Relay. — Mounted on top of the circuit breaker is
the series relay which provides the automatic overload feature.
This simple plunger type relay is calibrated for several values
above and below the normal operating current and will cause the
circuit breaker to open whenever the current equals or exceeds
the relay setting.

The liquid used in these circuit breakers, is a noninflammable
liquid of a very high dielectric strength. It is not only non-
inflammable but it is a fire extinguisher, and therefore has none
of the objectionable characteristics of oil. It has many of the
characteristics of Carbon Tetrachloride, but the boiling point is
very much higher than that of Carbon Tetrachloride. It is
necessary to use this liquid having a higher boiling point as
the circuit breakers are not hermetically sealed because of the
necessity for some clearance around the operating rod where it
enters at the top.

CHAPTER III
CARBON BREAKERS

Historical. — The previous chapter on automatic protection
gave an idea of the various cases where it is desirable to protect
circuits by means of fuses or circuit breakers. Fuses were among
the earliest means provided for securing automatic protection,
particularly in D.C. lighting plants. When the direct-current
railway system was started it was soon found that with 500 volts
or more, and the fairly large currents that were to be handled,
that fuse protection was not satisfactory and automatic circuit
breakers of different kinds were designed. The earliest circuit
breakers were practically knife switches with automatic features,
but the rapid burning away of the contacts necessitated some
means of reducing the vicious arcs that occurred when opening
the circuit.

Carbon Breakers. — One of the earliest designs that has stood
the test of time is a circuit breaker with auxiliary carbon con-
tacts. These auxiliary contacts remain closed until the main
contacts open and the carbons take the final arc. The fairly
high resistance of the carbon vapor in the arc and the fact that
the vaporized carbon was completely burned up aided in the
satisfactory operation of this device.

The principal demand for circuit breakers is to have them open
the circuit when the current reaches a certain predetermined
value, and breakers are designed with this end in view. They
are also built for underload conditions to open on minimum cur-
rent, for overvoltage to open when the voltage exceeds a certain
amount, for undervoltage to open when the voltage falls below
a certain minimum value and for reversal when the current
flows through the breaker in the opposite direction from that
which was intended. It is, of course, possible to combine these
various features of overload, underload, reversal, etc., in one and
the same breaker.

Owing to the impossibility of illustrating all capacities and
types of carbon break circuit breakers, the general features of

CARBON BREAKERS 37

carbon break circuit breakers are considered in considerable
detail and the distinctive features of different makes are illus-
trated by examples of a few representative ones.

Space Required. — The modern tendency is to economize in
space wherever possible. So much apparatus must be installed
in so little space that it is often necessary to choose the smaller
of two similar pieces of apparatus. A circuit breaker that gives
the required performance, and at the same time is small, often
means considerable saving in space.

Desirable Features. — It is essential that there be good contact
between the current-carrying parts of a breaker in order to
obtain the maximum current rating. Poor contact produces
local heating. A millivolt drop as low as possible is desirable in
a circuit breaker. This is best obtained by having perfect
contacts and current-carrying parts of ample size.

The carrying capacity of a breaker depends on the contact
and conductivity losses, the degree of ventilation, and the allow-
able temperature rise. The last point is of special significance.
In comparing the capacities of different breakers, the allowable
temperature rise must be taken into account in order to provide the
same basis of rating for each breaker; otherwise the ratings will
not afford a true comparison of capacities.

In order that a circuit breaker may give the best service it must
be easy closing. To obtain good service on the system, the
breaker must be "positive holding," that is, when it is closed,
it must stay closed until tripped by one of its tripping devices.
Vibration or stray fields should not open it. When a breaker
opens, whether tripped by the operator, by overload, or by any
other means, it is absolutely essential that its release be positive
and quick so that it breaks the circuit instantly. It should
never open sluggishly.

Dust and other foreign particles are liable to lodge on the con-
tacts of carbon circuit breakers. Repeated openings of the
breaker under load will burn the contacts slightly, making them
rough. In order that the dust may be cleaned off and that the
slightly rough surface may be kept smooth, a breaker should
have a self-cleaning action, that is, its contacts should be so
arranged that there is a slight wiping action between them
when they are being opened and closed.

A circuit breaker should be easily adjusted, but when set, its
adjustment should be permanent until changed by the operator.

38 SWITCHING EQUIPMENT FOR POWER CONTROL

A circuit breaker must be reliable. It should have positive
operation under all conditions. Better have none on the line
at all than have one that cannot be depended upon.

Temperature. — The current-carrying parts adjacent to the
contact surfaces of carbon circuit breakers should carry their
full-rated current continuously with a maximum temperature
rise of either 20 degrees or 30 degrees Centigrade, above the
temperature of the surrounding atmosphere.

The 20-degree rise basis is recommended when the maximum
temperature of the air where the breaker is located may approxi-
mate 40 degrees Centigrade and the load is practically continuous
as on generator, converter, or transformer circuits.

The 30-degree rise basis is recommended where the maximum
temperature of the air where the breaker is located may approxi-
mate 30 degrees Centigrade or less, or the load is intermittent,
as on feeder circuits.

The insulated coils of most carbon circuit breakers will carry
their full-rated current continuously with a maximum tempera-
ture rise. of 50 degrees Centigrade above the temperature of the
surrounding atmosphere.

Current Ratings. — The current ratings shown for all carbon
circuit breakers listed in makers' catalogues are maximum based
on the allowable temperature rise that is reached after a continu-
ous run of approximately one hour or more at the rated current.
Inasmuch as a circuit breaker reaches its final temperature
quickly with steady current load, it is necessarily a maximum
rated device. In selecting a breaker, it is, therefore, recommended
that the rated capacity should be at least as great as the maxi-
mum rated one-hour (or more) overload current of the apparatus
that the breaker will be required to control. Owing to the
"skin-effect" and eddy-current heating in alternating-current
conductors, a circuit breaker with the same rise in temperature
has a lower alternating-current rating than direct-current rating.
Also, on 25-cycle service a circuit breaker above 300-ampere
rating will carry continuously considerably more than its 60-
cycle rating.

Interrupting Capacity. — While the interrupting capacities of
most of the high-grade carbon breakers meet the requirements of
the National Electrical Code, and in certain cases are much
greater, it should be noted that the smaller types of various
manufacturers should not be connected too closely to apparatus

CARBON BREAKERS 39

or bus bars capable of delivering larger amounts of power than
specified by the Code. The relatively small wires ordinarily
used to connect these lower-capacity circuit breakers with sources
of power should be sufficient to introduce enough resistance to
limit the current that can be drawn through the breaker under
short-circuit conditions to the amount specified by the Code.

Intricate mechanism in a circuit breaker means endless trouble.
Simplicity should be looked for in every part.

Accidents that cannot be foreseen are always liable to happen,
and repairs must be made sometimes to the best breaker. A
circuit breaker should be so designed as to facilitate repairing,
and thus cause the least possible delay in putting it back in
service.

Distinctive features of the best types of carbon circuit breakers
are: exceptional ruggedness and neatness of appearance; sim-
plicity of construction, operation, and installation; few parts,
all easily accessible, and those parts likely to require replace-
ment, easily renewable; great compactness, thus saving in
space; long rigid carbon arms, giving long break of arcing
members; current-carrying parts of ample size so that no portion
of breaker will exceed guaranteed temperature rise; main
moving contacts are laminated copper brushes, self-wiping or
self-cleaning; auxiliary contacts in addition to main contacts;
self-aligning, self-cleaning carbon contacts; contact pressure
adjustable; low resistance from main contacts to carbon-arcing
contacts; small millivolt contact drop; very simple toggle
mechanism; all breakers trip easily, quickly and positively;
auxiliary tripping and signalling attachments are easily applied.

Construction. — In high-grade carbon circuit breakers special
attention has been given the problem of keeping the size of
breakers down to a minimum for the required performance.
The construction is such that the best possible ventilation is
secured, the object being to obtain the maximum radiating sur-
face on all current-carrying parts, and thus insure a breaker of
the highest current-carrying capacity for its size.

On the mechanically operated breakers, the closing mechanism
consists of the operating handle and the toggle mechanism con-
necting the handle lever and the main contact arm. On the
electrically operated breakers, the closing is usually effected by
means of a direct-current solenoid mounted below the main
mechanism. The solenoid plunger is connected to the closing

40 SWITCHING EQUIPMENT FOR POWER CONTROL

mechanism in such a way that when current flows through the
solenoid and the plunger is drawn into the solenoid, the main
contacts are closed.

The contacts of these breakers are held closed automatically
by a trigger or latch. The various trip mechanisms are con-
structed to disengage this latch and permit the breakers to open.

Main Contacts. — All current-carrying contacts are made of
copper. The movable element is a laminated brush composed of
several strips of copper and makes an end-on, or butt, contact
with the fixed element; this gives a relatively large wiping, or
self-cleaning contact when the breaker is closed and insures uni-
form pressure over the entire contact surface. A high contact
pressure is obtained because of the form of mechanism between
the handle and contacts. This pressure reduces the heating of
the contacts to a minimum and secures a low contact-resistance.
A means is provided for adjusting this contact pressure and for
equalizing the pressure on both ends of the moving element.

The main contact block, or fixed element, and the terminal
stud are of two forms: the round threaded form and the slotted-
bar or laminated form for laminated connections. In the
smaller capacities below 2500 amperes, direct current, they are
made up of drawn round or rectangular copper bar stock, elec-
trobrazed to form the terminal stud and contact blocks. In the
larger capacities, higher than 2000 amperes, direct current, they
are "pressure moulded" of extremely high-conductivity copper,
or made with laminated copper bars.

The slotted-bar studs are arranged with slots to take lamina-
tions running either vertically or horizontally, or with one stud
with vertical and the other stud with horizontal slots, thus
allowing the connections to the bus bars to be made in the most
convenient manner.

METHODS OF OPERATION

Under average conditions, for simple plants having not over
10,000-ampere 750-volt units, carbon circuit breakers can be
mounted directly on the switchboard panel. Where the require-
ments exceed these, remote-controlled breakers mounted apart
from the panel and electrically controlled from the panel by an
auxiliary circuit become advisable. For 1500- volt service in
capacities up to 2500 amperes the single-pole manually operated
remote-control breakers are recommended. Electrically oper-

CARBON BREAKERS 41

ated remote-controlled breakers are also made for lower capaci-
ties for applications where for other reasons it is preferred not to
mount the breaker directly on the panel.

Manual Operation. — Manual closing by a handle connected
directly to the breaker is the ordinary method of closing carbon
circuit breakers. Pulling down on the handle closes the breaker.

Electric Operation. — In the field of power operated carbon
circuit breakers the Westinghouse Electric & Manufacturing
Company and the General Electric Company adopted as stand-
ard the direct-current electrical-solenoid magnet method of
closing. The Cutter Company use various other methods, such
as motor, hydraulic and pneumatic closing in addition to sole-
noids.

Solenoid operated carbon circuit breakers of one design are
closed by means of a simple cylindrical magnet mounted below
the breaker mechanism. The solenoid is equipped with a dash-
pot device that takes care of the shock at the end of the closing
operation, and yet permits the breaker to close quickly. When
the closing switch is thrown, current flows through the solenoid
and the plunger is drawn down. This closes the contacts, which
are held closed automatically by a latch. The solenoid plunger
rises when the closing circuit is opened, so that it will not retard
the opening of the breaker when tripped. The breaker is opened
by the automatic overload trip or by the shunt-trip attachment
mounted at the side of the breaker mechanism. The breakers
can be tripped manually by pushing up on the operating handle
or back on the insulated trip handle near the bottom of the
breaker.

Standard closing coils are wound for direct current. Direct-
current mechanisms, besides being simpler in construction, more
reliable in operation, and more easily kept in repair, are much
more economical of space and power than alternating-current
mechanisms. Alternating-current shunts and current trans-
former trip coils are available in special cases.

The closing and tripping mechanisms are operated by a con-
trol switch with or without a control relay in the operating cir-
cuit, and usually with signal lamps. The electric operating
mechanism has a small double-throw switch to operate the signal
lamps and to open the shunt-trip coil circuit when the circuit
breaker has opened.

42 SWITCHING EQUIPMENT FOR POWER CONTROL

Acceleration. — On account of the reaction of the laminated
moving contact members, no separate means of accelerating the
breaker to its open position are necessary. The laminated mem-
bers, which act as powerful springs, the toggle-lever springs, the
secondary-contact springs, and the carbon-arm springs, all serve
to accelerate the opening of the breaker.

In general, carbon circuit breakers are made for either panel or
separate mounting. For separate mounting they are usually
furnished mounted on a slate base with black marine finish.

Non-automatic breakers are simply switches capable of opening
overloads, but opened and closed only at the desire of the opera-
tor. They can be made automatic through relays operating on
a shunt-trip coil.

Tripping Methods. — All standard overload-trip carbon circuit
breakers are plain-automatic, that is, when closed with an over-
load on the line, they will remain closed as long as the closing
handle is held down or the closing coil is energized, but will not
remain closed when the handle is released or the closing cir-
cuit is opened.

Full-automatic overload-trip breakers trip free of the handle
so that they cannot be held closed on a short circuit or overload.

All standard overload-trip carbon breakers are arranged for
direct acting (series) tripping without relays. In some cases
breakers used on alternating-current circuits are supplied for
transformer tripping. Breakers used on alternating-current
circuits and equipped with shunt-trip coils can be made
transformer-trip through relays acting on the shunt-trip coils.

Calibration. — The standard range of calibration for automatic
overload-trip varies with different makes. A typical range is from
80 to 160 per cent, of the 30-degree rise ampere rating. Breakers
can readily be set to trip at any point within their range. Cali-
bration higher than standard can be furnished in most cases.

SPECIAL ATTACHMENTS

Shunt-trip Attachment. — The shunt-trip attachment enables
the breaker to be tripped electrically from some distant point.
A direct-current shunt-trip mechanism is included as standard
with each electrically operated breaker and can be supplied as an
accessory on almost all manually operated breakers. If the cir-
cuit breaker is not arranged to cut out the shunt-trip circuit,
signal contacts should be provided to do this when the circuit

CARBON BREAKERS 43

breaker trips, as the tripping coils are designed for intermittent
service only. The automatic undervoltage-trip attachment
when supplied with a suitable resistor, can be used as a shunt-
trip mechanism by momentarily short-circuiting the coil.

Inverse Time Limit Attachment. — An inverse time limit dash-
pot with an adjustable time feature can be used with some
breakers. This attachment will cause the breaker to trip al-
most instantly on heavy overload and much more slowly on
light overloads, giving the circuit on light overload the chance to
clear the trouble before the breaker trips.

Automatic Undervoltage-trip Attachment. — The undervoltage-
trip attachment is used to trip the breaker when the line voltage
fails or falls approximately 50 per cent, or more under the rated
normal voltage. It is of particular advantage in automatically
disconnecting a motor from the circuit at the time of temporary
interruption of the supply circuit, for should the motor come to
rest and still be connected to the line it would be subjected to full
voltage upon the power being restored. The automatic under-
voltage-trip attachments for carbon circuit breakers are reset by
hand or automatically on the opening of the breakers according
to requirements.

Only one undervoltage attachment is necessary with multipole
breakers. No additional protection is afforded by the use of a
coil across each phase of a 2-phase or 3-phase circuit for
the reason that the motors, when the voltage of one phase fails,
will run single phase and feed back into the idle phase, thus
preventing the undervoltage device from acting; but the resulting
overload on the working phase, due to the entire load being on
that phase, will trip a properly set breaker.

The undervoltage-trip attachment, if supplied with suitable
resistor, can be used also as a shunt-trip attachment by momen-
tarily short-circuiting the coil.

Automatic Re verse -current Trip Attachment. — This attach-
ment is particularly applicable to storage-battery charging, or the
operation of direct-current generators or synchronous converters
in parallel, its function being to disconnect the generator from the
bus whenever the current reverses due to any cause, as for ex-
ample, rise in battery voltage, drop in generator voltage, or
stopping of the prime mover. It is not affected by an overload
in the normal direction, and can be applied to non-automatic
breakers where the reverse-current protection only is desired.

44 SWITCHING EQUIPMENT FOR POWER CONTROL

The automatic reverse-current trip attachment automatically
resets itself after the tripping operation and is prompt and
reliable in its action. Two windings are provided, one shunt and
the other series, the former having a shunt cut-out which auto-
matically opens the circuit when the breaker trips. If desired,
the tripping current may be obtained from a circuit other than
that in which the circuit breaker is connected.

The tripping range can be easily adjusted. If the shunt
coil is supplied with normal voltage, the Westinghouse attach-
ment can be set to trip the breaker at any current value from about
5 per cent, of normal rating in the positive direction to 25 per
cent, of normal rating in the negative or reverse direction. The
amperes required to trip the breaker will be affected only slightly
by small changes in voltage.

Automatic Overvoltage-trip Attachment. — The automatic over-
voltage-trip attachment is used principally in connection with
storage-battery charging, where it is desired to cut off the current
supply when the battery becomes fully charged. It may, how-
ever, be used in any alternating-current or direct-current circuit
which it is desired to open automatically in case of either mod-
erate or abnormal rise in voltage.

Automatic Underload-trip Attachment. — The automatic un-
derload-trip attachment is principally used on storage-battery
charging circuits. When the charging current decreases to a
certain predetermined value, the breaker is tripped; the circuit
is thus opened and the chance of current flowing back from the
battery to the generator and causing trouble is thus avoided.
For this application the attachment is generally set to trip at
10 per cent, of normal load, but the standard attachments can be
set to trip at any point from 10 to 25 per cent. The automatic
underload-trip attachments are reset by hand or automatically
by the opening of the breaker, according to service desired.

Signal Contacts. — For use as shunt-trip cut-outs and in
operating signal lamps, a single-pole double-throw plunger
switch that automatically closes one signal circuit when the
breaker is closed and another when it is open is supplied. This
attachment is fastened to the panel and is operated by an in-
sulated rod actuated from the moving main-contact brush of
the breaker. It has a switching capacity carrying from 10
amperes at 125 volts to 1 ampere at 750 volts.

CARBON BREAKERS 45

Bell Alarm Contacts. — For this service any small double-
throw single-pole switch can be used in conjunction with the
signal switch above referred to, for indicating by lamps, bells,
or other signal, the operation of the breaker. The signal contact
switch is connected as a single-pole, double-throw switch and,
in conjunction with the single-pole, double-throw, bell alarm
cut-out switch, makes the necessary connections to ring a bell or
operate a signal when the breaker is in the position opposite that
desired by the operator.

Relays. — Where a more reliable time limit is required for
selective operation of circuit breakers than can be provided by the
type of dashpot described above, protective relays should be used
in connection with the circuit-breaker shunt-trip coils. The use
of relays in connection with an auxiliary source of direct-current
power for tripping obviates the use of overload coils and time
limit features on the circuit breaker.

Field-Discharge Contact. — A combined shunt-trip and field-
discharge contact is usually supplied with the 2-pole form
of breaker for use in connection with exciter generators or
as main field switches to large alternating-current generators.
In this service the breaker is usually made non-automatic as
the excitation should only be interrupted at the will of the
operator. Reverse-current trip is sometimes applied to this
field-discharge form of breaker when it is used as the exciter-
generator main switch or breaker.

Double-arm Attachment. — The double-arm attachment elimi-
nates the necessity for switches in series with a 2-pole single-
handle breaker in low capacity and low voltage service and at the
same time affords automatic protection to the circuit throughout
the closing period. With this arrangement, each pole of the
breaker is closed independently and in succession, so that the
pole first closed is left free to open while the second or final pole
is being thrown in. The breaker being closed, an overload in
either positive or negative line, or both, will trip both poles simul-
taneously.

Trip-free-on-overload Attachment. — The trip-free-on-over-
load attachment (also known as "full-automatic-overload trip")
on a breaker makes it impossible to hold the breaker in a closed
position while a continued overload condition or short circuit
exists on the line.

46 SWITCHING EQUIPMENT FOR POWER CONTROL

Full-automatic or "trip-free" operation, particularly on direct
hand controlled carbon breakers, is not recommended for high-
capacity circuits or for service of over 250 volts D.C., or 440
volts A.C. Carbon breakers should not be closed on a circuit
under heavy load. Another switch should be used to close the
circuit, especially under overload; otherwise damage to the
secondary and carbon contacts, or injury to the operator, may
result.

In order to cover the field of carbon breakers in as complete
a manner as the space requirements will permit, typical breakers
of most of the important American builders are illustrated and
described without attempting to go much into detail regarding
any one breaker. A few diagrams are included of special cir-
cuit breaker features such as the connections of the "Auto
Reclosing Breaker," and the internal connections of a motor
operated breaker of the Cutter Company.

List of Makers. — Carbon break circuit breakers have been
made by a great number of different manufacturers, but the best
known ones are those that have been made by the following
American Works:

Automatic Reclosing Circuit Breaker Company, Columbus, O.

Condit Electrical Manufacturing Company, Boston, Mass.

Cutter Company, Philadelphia, Pa.

General Electric Company, Schenectady, N. Y.

Roller Smith Company, Bethlehem, Pa.

Westinghouse Electric & Manufacturing Company, Pitts-
burgh, Pa.

AUTO RECLOSING CIRCUIT BREAKER

Operation. — The Automatic Reclosing Circuit Breaker is a
magnetically operated breaker. There are three coils which
govern its action.

First. — The operating coil O, which closes the main contact
and holds the breaker closed.

Second. — The series, or overload coil, which causes breaker to
open in case of overload.

Third. — The trip coil T, which releases the lockout and per-
mits the breaker to reclose.

The accompanying cut, Fig. 28, shows the theoretical arrange-
ment of circuits with the breaker in the closed position. The
operating coil O is energized as follows: At point A the series

CARBON BREAKERS

coil is electrically attached to the main frame, and a circuit to
operating coil is made through cut-out contact C, to pin B, to
resistance R — 1, to operating coil O, to fuse L, and to opposite
side of line at M.

A high resistance R— 1 limits the current to the operating
coil to an amount just sufficient to hold the breaker in the closed
position but not enough to start it to close. An arm G is pro-
vided for the purpose of shunting R— 1 out of circuit while the
breaker is in the act of closing, so that full potential will be applied
to close the breaker. At the instant breaker closes, G is opened
by the main contact brush and held open by latch H.

Main Brush Contact

-*-To Generator

FIG. 28. — Auto-reclosing breaker
— closed position — diagram of con-
nections.

FIG. 29. — Auto-reclosing breaker
— open position — diagram of con-
nections.

Opening. — The breaker, being held closed magnetically, will
open either in the event of voltage failure or by the momen-
tary opening of the operating coil circuit.

Overload. — When an overload occurs the plunger of over-
load coils is raised so as to engage cut-out contact arm C and
cause it to rotate out of contact with pin B. This results in the
de-energization of coil O and the breaker opens.

Voltage Failure. — In case the voltage drops below that neces-
sary to maintain the magnetic seal of the operating plunger, the
breaker drops open.

Reclosing. — Fig. 29 shows the theoretical arrangement of
circuits with the breaker in the open position. After the breaker
has been opened due to any cause, it is necessary for trip coil T
to operate, and unlatch H so that arm G will cut out R-l.
This allows full potential to be applied to operating coil and closes
the breaker.

Before the trip coil can possibly act it is necessary that the
dashpot contact arm descend and close the circuit at K. This

48 SWITCHING EQUIPMENT FOR POWER CONTROL

provides a definite time interval during which the breaker must
remain open regardless of the cause of opening. While the main
contact brush is open a shunt path is formed from the positive
side of the generator around the main contacts through a high
resistance R-2 and a low resistance R-3.

Assuming a short circuit remains on the line and the dashpot
has settled down so as to complete the circuit for the trip coil, a
current I will flow through R-2. The value of the Resistance R-2
is relatively high in comparison with that of the trip coil and the
load or short circuit and R-3 which is in parallel with the trip
coil. For this reason a practically definite amount of current
will flow through R-2 regardless of the load resistance. But the
division of this current between the trip coil and load circuit will
depend upon the load or short-circuit resistance.

It will be observed that there are two paths whereby current
may flow from point D to point M. One of the paths being
through a low resistance R-3 to load through short circuit, and
back to M. The other path is through the trip coil and dash-
pot contact arm to point M. The trip coil is wound with a low
resistance so that a slight variation in the short-circuit resistance
will also cause a corresponding change of current through the
trip coil. So long as a short circuit of low resistance remains on
the load circuit the greater part of current I will be shunted
around the trip coil through the short circuit, as indicated by
I". However, as soon as the short circuit is removed or the
resistance of the short circuit increased to a value which would
not permit an excessive current to flow were the breaker to
reclose, enough current I will be forced through the trip coil to
cause its armature to rise and release latch which results in the
closing of breaker, after which the parts assume the position
shown in Fig. 28. The breaker does not close or attempt to close
while a short circuit or overload of low resistance exists, but does
close instantly and automatically upon the removal of short
circuit or overload.

Types. — These breakers are made in three different types,
depending on the current ratings. The smallest ones made
in capacities of 25 to 400 amperes are intended for the protection
of branch circuits and have contacts of solid copper with graphal-
loy arcing tips to take the final break. The medium size for
ratings from 300 to 800 amperes have laminated copper brush
main contacts, with secondary contacts of copper and graphalloy

CARBON BREAKERS

contacts to take the final break. The largest size, shown in Fig.

30, has contacts similar to the medium sized one. The operating
coil and trip coil are completely housed

and protected in a cast-iron frame which
carries the operating mechanism. These
breakers are built in capacities from
1200 to 2000 and modifications of this
type are built for 3000 and 4000 amperes.
These breakers are used for the pro-
tection of independent feeder circuits,
generator circuits, feeders in a network,
or for sectionalizing circuits and can be
arranged to take care of the many con-
tingencies in an automatic substation or
a plant where the class of attendance is
poor.

CONDIT CIRCUIT BREAKERS

Type K-2 breakers illustrated in Fig.

31, are made both front and rear con-
nected in capacities up to 300 amperes
at 600 volts B.C. or 750 volts A.C. with
underload trip, overload trip, under-
voltage trip, shunt trip, reverse power Large size.

FIG. 31. — Condit Electric Mfg. Co. circuit breaker type K-2.

and time limit. Various combinations of these different methods
of tripping may be applied to the same breaker. These breakers

50 SWITCHING EQUIPMENT FOR POWER CONTROL

are usually made hand operated but can be made electrically
operated.

Construction. — While the K-2 air circuit breaker has been
primarily designed for industrial application, its finish and general
appearance are such that it harmonizes well with instruments
and devices usually associated with switchboards.

It consists essentially of three distinct standard units: (1)
the upper contact member with its auxiliary metal and carbon
contacts, stud and nuts; (2) the movable contact members,
comprising the brush with its metal and carbon auxiliary contacts
and the operating mechanism, supported by the housing; (3)
the tripping coil with its stud, magnetic circuit and calibration
plate.

The conducting parts are liberally designed, and the laminated
brush is fully protected by relatively massive carbon auxiliaries
on which the arc is finally broken. Interposed between the
laminated brush and the carbon contacts is a metal auxiliary
contact so related to the main brush that proper protection to
the current-carrying members is assured. The carbon and metal
auxiliary contacts are easily renewable and reversible.

A vibration proof latch holds the breaker normally in the closed
position and when released by the tripping coil the moving con-
tact member opens positively and quickly. The magnetic cir-
cuit of the trip coils is laminated. This feature is of importance,
as it renders overload breakers interchangeable for use on either
direct or alternating-current circuits. The breaker is easily
closed by a downward movement of the handle, and the mechan-
ism is so arranged that the brush pressure is properly distributed.

Double-pole breakers are arranged for independent closing,
but both poles trip simultaneously on overload. Three-pole
breakers are arranged with a common handle, causing all poles
to be closed and opened simultaneously. Four-pole breakers are
not arranged so that all poles are closed simultaneously — two 2-
pole breakers are furnished, each having a common handle which
causes the two poles to be closed and opened simultaneously.

Barriers are furnished on all multipole breakers above 250
volts D.C. or 440 volts A.C. -

Trip Range. — Standard overload breakers, for use on both di-
rect and alternating-current circuits, are calibrated from 80 to
160 per cent, of full-load current.

Air circuit breakers which are seldom opened in the course of

CARBON BREAKERS

regular operation should be periodically opened and thoroughly
cleaned.

Type K-l breakers shown in Fig. 32 are made in capacities
from 100 amperes to 5000 B.C., 4400, 25 cycle, 3300, 60 cycle,
in 1, 2 or 3 poles and as 6000 and 8000 ampere D.C. single
pole for plain overload, plain shunt trip or undervoltage with

FIG. 32. — Condit type K-l carbon breaker.

various attachments to secure time limit, reverse power or
other features. These breakers are made with round studs up to
the 2000-ampere D.C. size and with laminated studs for the larger

CUTTER— I.T.E. CIRCUIT BREAKERS

The Cutter Company make their "I.T.E." breakers. in various
forms and capacities for hand operation or electric control de-
pending on the class of service for which they are intended.
They adopted the "I.T.E" designation as their earliest breakers
were designed to have an "Inverse Time Element" as one of
their principal features, the time of tripping being in an inverse
ratio to the severity of the short circuit.

Types. — For 250-volt service in capacities from 5 to 300 am-
peres the E-l type of breaker is furnished where compactness

52 SWITCHING EQUIPMENT FOR POWER CONTROL

FIG. 33. — Cutter type LL carbon breaker.

FIG. 34. — Cutter type LG carbon breaker.

CARBON BREAKERS

is an important feature, this breaker being on a base only 5%
inches wide and 7 inches long.

For capacities from 80 to 1250 amperes at 250 volts or less, the
type N-X is used. To secure uniformity of appearance on a
switchboard all of the breakers are built on the same frame. If
desired these breakers can be provided with no-voltage feature,
shunt-trip feature, time limit and bell ringing attachments.
The breakers can be made multipole with independent closing
arms so that they are adapted for use on distributing circuits
without any switches in series with them.

For use on circuits of 750 volts or less the L-L type is built for
currents from 200 amperes up to 1600 amperes D.C. or 1250 am-
peres A.C. As shown in Fig. 33 the brushes of laminated con-
struction rest on the contact blocks at an angle, while for the
larger L-G breakers shown in Fig. 34, made in capacities up to
10,000 amperes D.C., the laminated brush is of the end-on butt con-
struction that is found advantageous in large capacity breakers.

FIQ. 35. — Cutter circuit breaker — sectional view.

Operation. — Fig. 35 shows a sectional view of a typical
"I.T.E." breaker and the description of the main parts of the
breaker and its overload features may be considered as that of

54 SWITCHING EQUIPMENT FOR POWER CONTROL

a normal high-class American breaker, although those of other
makers naturally differ in the details of construction.

The illustration, Fig. 35, shows the details of one form of
I.T.E. Circuit Breaker Switch Member. 98 and 50 are fixed
terminals mounted upon the front of the base or switchboard.
The current entering the instrument at 50 by way of the rear con-
nection stud (not shown), passes through the overload coil 50a
into the contact block SOB, thence it passes through the lami-
nated contact member or bridge 16, into the upper terminal
and out at the rear by way of a threaded stud (not shown). A
by-pass of somewhat higher electrical resistance than that of the
main contact member is offered by the flexible copper strip 3,
through which the current from the lower contact block passes
to the spring plate 30, thence to secondary metallic contacts
69 and 81 and the final or breaking contacts 27 and 75, which
consist of carbon blocks.

The action in opening the circuit is as follows: The laminated
member first moves out of contact with the terminal 98, co-inci-
dent with which the current is shunted through the secondary
path which, though of higher resistance than the main contact
member, has sufficient conductivity to prevent the formation
of any arc at the main contacts. The circuit between the sec-
ondary metallic contacts 69 and 81 is next interrupted, through-
out which action the carbons are maintained in full contact.
The circuit is finally broken by the separation of the carbons
which are highly refractory, and upon which the action of the
current is not such as to impair their usefulness.

The most widely used circuit breakers are those which open
in the event of overload or excessive current. The operation of
the overload feature depends upon the volume of current only,
regardless of its direction and is independent of the voltage of
the circuit.

Overload Feature. — One form of I.T.E. overload feature is
shown. The principal parts are an armature 127 and magnet
59 energized by a winding 50a, carrying the main current of the
circuit in which the circuit breaker is connected. The armature
is pivoted on pins 128, and is normally held by gravity out of
engagement with the magnet against an adjustable stop 136,
and is adapted, when the current exceeds a predetermined value,
to be drawn forcibly against the magnet, toward the completion
of which movement it impinges upon the latch 87, which nor-

CARBON BREAKERS 55

mally holds the switch member of the circuit breaker closed
against the action of the opening springs. The normal or "at
rest" position of the armature is subject to convenient adjust-
ment by movement of the stop 136, by means of knob 11, so that
the distance between magnet and armature may readily be
varied, the volume of current required to move the armature into
engagement with the latch being correspondingly varied; the
closer the armature is to the magnet the less the current required
to actuate it to trip the circuit breaker. The volume of current
which will cause operation of the overload feature at various
positions of the armature is suitably indicated along the calibra-
tion scale 13.

Reversite. — Where D.C. generators operate in parallel or are
used with a storage battery a reverse-current feature is usually
found advisable to cut off a generator if the other generators or
the battery tend to force current into the unit. The term
"Reversite" is applied to these Cutter breakers that have this
reverse-current feature.

Remote-control circuit breakers and switches have the advantage
that they do not require to be massed together upon a single
switchboard, but may be located in such a manner as will afford
the most convenient and economical cable installation; for while
remote-control apparatus may be scattered around in various
parts of the plant as conditions dictate, the control may readily
be brought to any point determined upon as the most convenient
for this purpose. The switches and indicating devices for con-
trolling a large number of circuit breakers may be placed upon a
bench board of insignificant dimensions, so that a large installa-
tion may be placed, by this means, virtually under the eye and
within easy reach of a single operator.

Motor Operated. — The reliability of motor operated circuit
breakers depends in no small degree upon the perfection of
apparently minor details, and every such feature is given most
careful attention.

The motor operated device for closing a circuit breaker must
fulfill two conditions : it must, regardless of voltage variations in
the control circuit, communicate to the circuit breaker the exact
movement required to latch it, and it must instantly disengage
from the circuit breaker when the act of closing is completed.
As the result of failure to fulfill either of these conditions the
circuit breaker would remain under the restraint of the closing

56 SWITCHING EQUIPMENT FOR POWER CONTROL

mechanism and would fail to respond properly to overload or
other abnormal condition which should cause its opening.

The means employed to meet these very exacting require-
ments are indicated on Fig. 36, where the essential working parts
of the I.T.E.Motor Operated Circuit Breaker are diagrammatically
shown. The movement of the motor in closing the circuit
breaker is communicated to a gear sector A by means of a
worm B, ball and socket jointed to an extension of the arma-

FIG. 36. — Cutter circuit breaker — motor operated.

ture shaft. The gear sector is in turn connected by means of a
link C to the circuit-breaker operating arm. Except during
the act of closing the circuit breaker electrically, the worm is held
out of mesh with the gear sector by the toggle D, which is
acted on by the weight of the magnetic core M. This core is
adapted to be lifted by the engaging coil E when same is duly
energized. The circuits of both motor and engaging coil, which
is connected in parallel with it, are under control of the timing
switch F. The relations between this switch and the circuit

CARBON BREAKERS 57

breaker are such that when the circuit breaker is open, the switch
is closed, and vice versa.

With the circuit breaker open, and the timing switch in its
corresponding closed position, the motor may be brought into
operation from the control station by means of an appropriate
switch indicated at H. This starts the motor through the
resistance J, and also energizes the engaging coil, which,
through the plunger acting on the toggle D, forces the worm
B into engagement with the gear sector A, which in turn
communicates the movement of the motor to the circuit breaker
through the link C. The movement of the toggle D is also
communicated to the localizing switch I which connects
the motor directly with the control circuit and renders its further
movement independent of the control switch. At the comple-
tion of the closing movement, the stop K on the gear sector
comes into engagement with the bell-crank lever G, causing
it to open the timing switch, thus disconnecting the motor and
engaging coil; the heavy core M associated with the latter
is then directed upon the toggle D, disengaging the gears so
that further movement of the motor armature will not be com-
municated to the circuit breaker. The disengagement of the
gears is further insured irrespective of the action of the timing
switch by the upper arm of the bell-crank lever being directed,
in its final movement, against an extension N of the toggle,
forcing it into the open position. Should the motor overtravel
from any cause whatever, its own excess movement thus serves
to disengage it from operative connection with the circuit
breaker.

Should abnormal current condition exist upon closing, the
circuit breaker is ready to respond instantly and opens immedi-
ately without restraint or drag from the operating mechanism.
The final movement of the circuit breaker in opening is com-
municated through the stop L to the bell-crank lever, thus
closing the timing switch and again placing the motor circuit in
condition to be closed from the control station. The position of
the circuit breaker, whether open or closed, is indicated by the
lamps associated with the control switch.

Solenoid Operated. — The magnetically operated circuit
breaker of the overload type shown in Fig. 37 may be closed on
normal load, but immediately releases if closed electrically on
overload; hence, the usual switch in series may be omitted, a

SWITCHING EQUIPMENT FOR POWER CONTROL

provision allowing the utmost simplification of switchboard
construction. The cable installation in conjunction with direct-
current generators operating in parallel may often be greatly
simplified by using these breakers (made without overload
feature) as equalizer switches. By mounting them on pedestals
alongside of the respective generators they materially shorten

FIG. 37. — Cutter circuit breaker — solenoid operated.

the equalizer leads, rendering it unnecessary to run these cables
to the switchboard. This is of especial advantage where the
switchboard is located at a considerable distance from the
generators.

Among the various mediums employed for the actuation of
mechanical devices, none has proved more reliable under a
wide variety of most exacting conditions than compressed air.
The air brake, the electro-pneumatic signal and the pneumatic
drill offer convincing illustrations of this fact. Exposed to
changing atmospheric conditions and sometimes handled by
the roughest class of labor, they do their work with unvarying
reliability and effectiveness.

CARBON BREAKERS

Pneumatically Operated.— The I.T.E. pneumatically operated
remote-control circuit breaker, Fig. 38, embodies the simplest
possible method of controlling the circuit breaker from a dis-
tance. The operating feature consists primarily of a double-
acting piston moving within a cylinder, each end of the latter
having a valve-controlled connection with the compressed air
supply. The circuit breaker is opened by a movement of the
control valve in one direction admitting
air to the upper end of the cylinder; the
closing of the circuit breaker is caused by
an opposite movement of the control valve
admitting air to the lower end of the
cylinder.

The circuit breaker furnished in con-
nection with the class of control has the
"Autoite" feature, allowing the switch
member to open independent of the move-
ment of the closing arm. Should the at-
tempt be made to close the circuit breaker
upon overload, it is free to respond in-
stantly and without restraint from the
closing mechanism. After it has been so
opened, two movements of the control
valve are necessary to close it; one move-
ment admitting air to the upper end of the
cylinder, forcing the handle lever into en-
gagement with the switch arm; a second
movement admitting air to the lower end

VT £ii i- ii. • -i cuit breaker — pneumatic

of the cylinder, finally closing the circuit operated,
breaker. Where the operator is sufficiently
near the circuit breaker to have it in view, the control valve
may be operated by hand. Where the instrument is located
at a considerable distance from the point of operation, the valve
may be operated electrically, suitable signals at the point of
control indicating the open and closed positions of the circuit
breaker.

The simplicity and ruggedness of this type of apparatus
especially adapts it for use in mills and foundries; also to in-
stallations in which the apparatus is exposed to atmospheric

FIG. 38. — Cutter cir-

SWITCHING EQUIPMENT FOR POWER CONTROL

Electro-pneumatic. — Fig. 39 shows a remote-control I.T.E.
circuit breaker with electro-pneumatic control. It is of 6000-
amperes capacity for 600-volt service, and illustrates one of a
considerable number made for a large metropolitan railway system.
These circuit breakers are mounted in stations along a portion
of the road and form the connections between successive sections
of the third rail. They are used to automatically disconnect
such sections of the rail as may be
grounded and to reconnect them
when normal conditions- have been
re-established.

The system in which these circuit
breakers are installed was already
supplied with compressed air equip-
ment used for operating signals and
there were also a number of tele-
phone cables available for use as
control circuit wires. These condi-
tions made the installation of com-
pressed air operated apparatus
especially economical and had con-
siderable weight in determining the
selection of this type.

GENERAL ELECTRIC CIRCUIT
BREAKERS

The General Electric Company
have a very complete series of carbon
circuit breakers for various kinds of
service. For light duty in isolated

plants, the type CG is furnished for A.C. or D.C. service in
capacities from 3-300 amperes for voltages below 550 D.C. or
600 A.C. and these can be furnished for overload, underload,
shunt trip, reverse current, undervoltage and combination of these.
Type CP.— The CP breaker shown in Fig. 40 is a high-grade
switchboard breaker, made in capacities from 15-1200 amperes
for A.C. or D.C service in voltages up to 650, with the various
methods of tripping and the usual attachments.

The force applied to the handle closes the breaker through a
simple strong toggle mechanism which acts directly on the brush.
The toggle joint gives a very heavy pressure at the brush with

FIG. 39. — Cutter circuit
breaker — electro-pneumatic.

CARBON BREAKERS

minimum pressure on the handle, making the breaker very easy
to close. The heavy brush pressure insures good contact and
also assists in rapid opening when the breaker is tripped.

FIG. 40. — General Electric Co. circuit breaker type "CP."

Contacts. — The main brush is of special form. Laminations
make "end-on" contact with heavy and uniform pressure over
entire contact surface without tendency to force any part of
brush out of contact. The cross-sectional area of the brush
is ample for the amount of current it is designed to carry, and
the form of the brush permits the maximum pressure between the
laminations and the contact block.

A burning tip is provided for each pole so that burning of the
main brush is prevented. Burning tips close with wiping action.
They are easily replaced at small expense.

Secondary contacts are solid blocks of selected carbon, shaped
to fit accurately in the holders to which, after being copper plated

62 SWITCHING EQUIPMENT FOR POWER CONTROL

FIG. 41. — General Electric Co. circuit breaker type CK.

FIG. 42. — General Electric Co. circuit breaker type "CP3."

CARBON BREAKERS

and tinned, the carbon contacts are securely sweated. No screw
holes or grooves are used in the carbons. The carbon contacts
are closed under pressure with a wiping motion which insures
good contact.

FIG. 43. — 12,000-amp. G. E. carbon-break circuit breaker.

When the breaker opens, the brush first breaks contact; next
the burning tip and finally the secondary carbon contact. This
sequence of operation prevents all burning of main brush contacts.

Type CK. — The type CK is a high-grade switchboard breaker
for 250 volts D.C., 1500-6000 amperes and for A.C. 480 volts,
1500-3500 amperes. The CK-2 is intended for 650-volt service
and is built in sizes 1500-10,000 amperes D.C. and 1500-3500

64 SWITCHING EQUIPMENT FOR POWER CONTROL

A.C. These breakers are shown in Fig. 41, the main difference
in the two types being in the length of the carbon arms. Their
general features are like the C.P.

On the CK-2 breaker, the arm carrying the carbon secondary is
locked in position under full pressure until the main brush has
opened a certain distance, after which the secondary contact
arm rapidly swings forward and widely separates the secondary
contacts. Current passing through the breaker energizes the
magnetic circuit around the lower stud and attracts the armature,
which strikes the latch a hammer blow
and trips the breaker.

A positive locking latch holds the
breaker closed. Latch is so con-
structed that breaker will not jar
open, but will trip easily without aid
of accelerating devices.

Solenoid Operated. — For solenoid
operation the breakers are designated
as CP-2 and CP-3 and these contain
the same features as the corresponding
hand operated types. The arrange-
ment of the solenoid mechanism is
shown in Fig. 42. The plunger of the
closing coil acts directly on a simple
toggle to close the breaker and the
construction is such as to give a very
heavy pressure on the brush contacts.
A removable handle is conveniently
located and insulated from the live
parts of the breaker. A removable
handle is provided for inserting in a
socket of the mechanism for hand closing.

Heavy Breakers. — Special breakers for very heavy A.C. cur-
rents are usually made with the solenoids mounted separately
from the breaker, as shown in Fig. 43, this being a breaker fur-
nished to the American Woolen Company, at Lawrence, Mass.,
to carry 12,000 amperes continuously at 40 cycles, 600 volts.

Motor Operated. — An interesting combination of motor oper-
ated carbon breakers and brush type of switch is shown in Fig. 44,
of which there were 190 switches furnished on the original con-
tract for the substations of the New York Central Railway.

FIG. 44. — General Electric
Co. circuit breaker motor
operated with switch.

CARBON BREAKERS

When the control switch is manipulated on the switchboard the
motor is started and the carbon break circuit breaker is closed.
Further rotation of the motor disconnects it from the breaker
mechanism and connects it to the switch mechanism which it
closes in turn. If there is a short on the circuit the breaker is
free to trip out and open the circuit.

ROLLER-SMITH CIRCUIT BREAKER

The Roller-Smith breaker is made in capacities of 5 amperes
to 6000 amperes for 250 volts and 600 volts, multipole breakers
being built up to 1000 amperes and the large ones being made
single pole only. The breakers can be supplied for overload or
underload or both and reverse current and other features can be
secured through relays.

CROSS-SECTIONAL VIEW
FIG. 45. — Roller-Smith carbon-break circuit breaker.

The R-S breaker shown in Fig. 45 is closed by pulling down the
handle to the position shown in cut. The arm is under compres-
sion against the brush and tends to open on account of the spring
of its coil, but it is held closed by the roller on the handle (which
is slightly over the center line between handle bearing and roller
on arm). A slight kick from the armature knocks it back across
the center line and the breaker flies open. There are no latches
or triggers to hold arm closed, merely the rollers which are non-
rustable and practically without any wear.

There is an eccentric pin stop for the roller which limits the
distance it passes over center. The breaker may thus be made

66 SWITCHING EQUIPMENT FOR POWER CONTROL

more or less sensitive as desired. This cut shows the construc-
tion in sizes over 1200 amperes, in which the laminations are
continuous from brush to bus bar. In other respects the con-
struction of smaller sizes is similar.

The industrial type of circuit breaker is built in capacities
up to 100 amperes for voltages up to 250 D.C. and 440 A.C.
They are made either front or rear connection and are of simple
and rugged design.

WESTINGHOUSE CIRCUIT BREAKERS

The Westinghouse Electric & Manufacturing Company, who
were one of the first to develop the Carbon Circuit Breaker,
have complete lines of breakers from the type F that is built
in capacities up to 75 amperes, 250 volts, up to the largest
capacity for which there is any demand.

Type F. — The type F are small, and compact single-pole
carbon breakers. They readily take the place of switches and
fuses and occupy about the same space as a fuse block and fuse.
They are designed to fulfill a demand for a protective device to
be used with small motor and lighting installations, and have a
cost commensurate with those of such systems.

The overload-operating solenoid is inside a fibre tube form-
ing the lever arm. The tripping point may be set for any current
within the tripping range by a little knurled thumb screw located
below the pivot. A small insulating knob at the right controls
the tripping device and offers a means of opening the breaker by
hand.

The current-carrying contacts are copper, the arcing con-
tacts are carbon and are readily renewable. The lower arm is
operated by a spring and the copper contacts are of a shape to
assist in opening the breaker.

Type CD. — Type CD carbon circuit breakers shown in Fig.
46 are supplied for separate or panel mounting. These breakers
are supplied for voltages up to 750 and for capacities up to
300 amperes. They may be used for motor starting-control
of industrial circuits and as feeder circuit breakers in moderate
size. The main or brush contact is made of laminated copper
having high-pressure contact with an excellent wiping or self-
cleaning action. When the breaker is opened, the main contact
is opened first and the current is shunted upward through auxili-
ary contacts where the circuit is broken. The secondary contacts

CARBON BREAKERS

FIG. 46. — Westinghouse carbon circuit breaker, type CD.

FIG. 47. — Westinghouse circuit breaker type "CC.'

SWITCHING EQUIPMENT FOR POWER CONTROL

are of flat phosphor bronze. The arcing contacts are of carbon
and have a wiping action, making them self-aligning and self-
cleaning.

Type CC. — The type CC carbon circuit breaker shown in
Fig. 47 for protection of alternating-current and direct-current
circuits of moderate capacities are supplied for voltages of 750 or
less and for capacities up to 800 amperes. These breakers are
manually operated and are closed by pulling down on the operat-
ing handle, and may be tripped manually by pushing upwards
on the handle or back on the calibrating thumb knob. In
closing a breaker, the brush is forced against the contact plates
by means of a toggle-joint lever. A small steel roller engages a
locking catch, places the two releasing springs under tension,
and holds the breaker in the closed position. Friction clips, which
engage a projection on the handle eliminate any destructive
effects of jarring due to the opening of the breaker.

FIG. 48. — Westinghouse carbon circuit breaker, type CA.

Contacts. — The main contacts are made of laminated copper
brushes and attached to the upper end of each movable contact
is a phosphor-bronze secondary contact that bears on the main
stationary contact when the breaker is closed, and opens after
the main brush has entirely left the contact plate. By this
means, the opening of the circuit is transferred from the main

CARBON BREAKERS

contacts and, in case of any possible failure of the carbon arcing
contacts, the main contacts are protected from, the arc.

Each breaker is also provided with auxiliary carbon arcing
contacts which finally interrupt the circuit, thereby preventing
any burning of the main contacts when the breaker opens. The
stationary carbon contact is securely fastened to the stud im-
mediately above the upper stationary main contact. The mov-
able carbon contact is mounted immediately above the movable
main contact to which it is connected by a shunt composed of
braided flexible copper. This contact is so mounted that the
main and secondary contacts are open about one-quarter inch
before the carbons separate, thus eliminating any possibility
of the metallic contacts being blistered by the arc. The movable
carbon contact is pivoted on the supporting frame in such a
manner that it is in perfect alignment with the stationary contact
whenever the breaker is closed. These carbon contacts are
inexpensive and readily renewable.

Type CA. — Type CA carbon circuit breakers, Fig. 48, are
designed particularly for the severe current-carrying and inter-
rupting conditions found in operating low voltage direct and
alternating-current systems. They are made in the following
capacities, based on 30-degree Centigrade rise :

MAXIMUM AMPEHES

For circuit

Manually

Max.

operated

Electrically

Current

Frequency
cycles

volts

direct
control

remote
control

operated

Direct

( 750
\ 1,500

24,000

2,500

24,000
8,000

Alternating ....

(28

750

10,000

\ 60

750

7,000

Distant Control. — When conditions make it desirable to
operate carbon circuit breakers from a distance, the electrically
operated form or the manually operated remote control, within
its limited application, is furnished. This makes it possible to
install the circuit breaker near the apparatus to be connected,
like the equalizer connection of a direct-current generator, and to

SWITCHING EQUIPMENT FOR POWER CONTROL

retain the control at the switchboard. Another common applica-
tion of the electrically operated form is for remote-control
feeder tie switches on distributing systems. Such arrangements
effect a saving in wiring, as a light control cable takes the place
of the heavy power cable otherwise required.

The simple form of toggle mechanism used throughout is
especially worthy of note. This toggle on all sizes, from 3000

to 24,000 amperes, consists of
but a single link member con-
necting the handle lever and
main contact arm, but is so
shaped and related to the
lever members as to form an
eccentric toggle of exceptional
power. In the sizes below
3000 amperes the toggle is of
the roller type, formed by
means of a roller on the inner
end of the handle lever acting
directly on a plane surface on
the brush-arm or main con-
tact lever. Both forms are
best adapted to the particular
sizes of breaker and form the
simplest mechanism known to
be used for the purpose. The
automatic overload tripping
attachment is contained in the
circuit breaker and forms an
integral part of it.

Contacts. — In larger
capacities, where the moving
contact is subdivided in order

FIG. 49. — Westinghouse Type CA breaker
— contact arrangement.

to obtain a better average distribution of contact pressure, large
ventilating spaces are allowed between the individual laminated
main contact members. This reduces the temperature rise very
materially under any given conditions of load and increases the
capacity on alternating-current service by reducing the "skin
effect." When the breaker is tripped, the main contacts are
opened first and the current is shunted upward through copper
secondary and tertiary contacts to the carbon arcing contacts
where the final break takes place. See Fig. 49.

CARBON BREAKERS 71

This shows the shape and relative position of each of the
contacts in the three important stages of breaking the circuit, as
follows :

1. Contacts outlined by dotted lines show main brush opened,
secondary contact on point of opening and tertiary and carbon
contacts not changed from closed position.

2. Contacts shown by light shading show main and secondary
contacts open, tertiary and carbon contacts still closed, but one
set of contacts has slid down on the other set.

3. Contacts shown by heavy shading show the tertiary contact
open and carbon tips about to finally break the circuit.

Directly over the brush contacts the secondary contacts are
located. The secondary stationary contact has a surface in-
clined to the vertical and practically parallel to the plane of
support of the moving contact spring, thus preventing buckling
of the spring in case the contact is roughened by repeated opening
under short-circuit conditions. The moving contact spring is
held under initial pressure until just before the contacts separate.
The secondary contacts open next after the main or brush con-
tacts open, protecting the latter from arcing under severe short-
circuit conditions.

An adjusting screw on the moving contact allows an adjust-
ment of the relation of the opening of the main and secondary
contacts.

The tertiary contacts are attached to the lower end of the
carbon contacts of which they appear to be a part. They are
made of copper and are connected to the main or brush contacts
by heavy copper shunts. They open immediately before the
carbon contacts open and fully protect the secondary contacts
except under extreme conditions of repeated short circuit with-
out proper maintenance.

The carbon or final contacts, except where exposed to the arc,
are heavily copper coated or filled, thus insuring lowest-resistance
contact with the tertiary-contact copper plates and the shunts to
the main contacts. They are self-aligning and have a self-
wiping action, thus making them self-cleaning.

The carbon arms are of ample length and open far enough to
insure breaking the heaviest arc incident to short circuit, as in
heavy railway service.

Contactor Type. — A line of breakers known as the type CA
contactor-type circuit breaker (see Fig. 50) is available in capa-

72 SWITCHING EQUIPMENT FOR POWER CONTROL

cities from 1000 amperes to 8000 amperes direct-current, inclu-
sive, and in intermediate capacities corresponding to the regular
type CA single-pole line. The term "contactor type" means a
breaker that is electrically operated, but held in the closed posi-
tion by the presence of a small amount of closing current on the
operating magnet and not by a mechanical latch, as is usual
with the standard manually or electrically operated type CA
breakers. The breaker drops to the open position on the absence
of voltage in the control circuit. The contactor type of electri-
cally operated breaker is much more simple
than the standard electrically operated form,
which has all of the parts of the regular man-
ually operated breaker and the electric operat-
ing mechanism in addition. However, they
are made only in the single-pole non-automatic
form, which accounts for part of the simplicity.
The contactor breaker is made automatic
by the addition of overload or reverse power
relays arranged to open the closing coil circuit
or to short-circuit the closing coil with re-
sistance in series. The latter relay scheme
permits the use of standard contact-closing
relays.

The contactor breaker is adapted for use
as an automatic feeder tie switch in con-
junction with appropriate relays and con-
nections. In this service it is adjusted to
open when the voltage drops below a certain predetermined
limit, as would be caused by an excessive overload or short
circuit in the vicinity. The breaker will then remain open
until some predetermined voltage exists on both feeders that it
is arranged to tie, and then automatically closes.

Multipole contactor breakers are made by using several single-
pole units controlled by a single control switch or relay or both.
Manually Operated Remote -control Breakers. — For service
up to 1500 volts direct current and capacities up to 2500 am-
peres, single-pole type CA manually operated breakers are sup-
plied for mounting above or away from the switchboard panels,
but operated from a handle mounted on the panel in the usual
location for the knife switch. See Fig. 51.

FIG. 50. — Westing-
house contactor type
breaker.

CARBON BREAKERS

FIG. 51. — Westinghouse remote-control 1500-volt breaker.

FIG. 52. — Westinghouse electrically operated breaker.

74 SWITCHING EQUIPMENT FOR POWER CONTROL

Multipole Circuit Breakers. — Each multipole breaker is pro-
vided with a common trip; that is, an overload on any one pole
trips all poles. The manually operated breakers (two, three"or
four-pole), up to and including 2500-amperes capacity can be
provided with a single closing handle and crossbar for closing all
poles together (all poles tripped together). This form of handle
is arranged, by springs, to retrieve independently of the breaker
pole units so as not to retard the operation of the breaker on
opening.

Solenoid Operated. — The electrically operated multipole
breakers, Fig. 52, are supplied in any standard number of poles
and in any standard ampere capacity in which the type CA
line is listed. They have a common electromagnet for closing
all poles and a single shunt-trip magnet acting through a common
trip mechanism for tripping all poles of the breaker together.

Direct-current shunt-trip attachments arranged for mounting
on the front of the panel are made for all capacities of manually
operated type CA breakers.

A direct-current automatic undervoltage-trip attachment is
made for the several capacities of type CA breaker. This
attachment is reset automatically by the opening of the circuit
breaker.

An inverse time limit dashpot with an adjustable time feature
is made for all sizes of CA breakers up to and including 2500
amperes direct current and 1600 amperes alternating current,
in any number of poles up to four poles, and for both manually
and electrically operated breakers. A similar attachment for
the larger capacity breakers can be supplied.

An attachment for tripping the type CA carbon circuit
breaker on reversal of current in direct-current service is made to
be applied to any regular type CA carbon circuit breakers of
capacities up to 20,000 amperes.

CHAPTER IV
OIL CIRCUIT BREAKERS

Application. — It is generally conceded that for opening large
amounts of alternating-current power and for controlling all
alternating-current high voltage circuits nothing at the present
time is superior to oil circuit breakers. There are three funda-
mental reasons for this : First, the fact that this type of breaker
terminates the alternating-current wave at its normal zero value,
eliminating excessive surges in the connected circuits; second,
the compactness of form of the apparatus; and third, the fact
that this type of apparatus properly designed reduces the fire
and life hazards to a minimum.

When an oil circuit breaker is opened under load, an arc is
formed between the stationary and the moving contacts, the
size of the arc depending upon the voltage, the amount of current,
and rate of contact separation. The heat of the arc disintegrates
some portion of the arcing contacts and some of the oil surround-
ing the contacts, forming a gas bubble of a size that depends on
the amount of current flowing and on the duration of the arc.
If this gas bubble is immediately carried away from the con-
tacts and the contacts have been sufficiently separated, the arc
will persist only until the next zero of the current wave. The
ability of the bubble to rise away from the contacts depends
upon the relative specific gravity of the gas and oil, and the
head, volume, and viscosity of the oil. Oil having high specific
gravity and sufficient head will exert pressure enough to force
the bubble up and away from the contacts, irrespective of their
position.

Features. — The following features apply to practically all
high-grade American oil-circuit breakers of any make, and are
generally recognized as embodying the best practice.

These are: open position maintained by gravity, so that the
contacts fall to open position in case of injury to the moving
contacts or the lifting rods; the rapid acceleration of the moving
parts on opening to minimize the duration of arcing, the tank

76 SWITCHING EQUIPMENT FOR POWER CONTROL

pressure, and the deterioration of the arcing contacts; all live
parts immersed under a deep head of oil to absorb the shock of
short circuits and to prevent the excessive development of gases
when rupturing large amounts of power; proper venting and
baffling arrangements for oil tanks to provide regulated escape
for the gases formed by rupturing heavy overloads and short
circuits; sturdy mechanical construction throughout; isolation of
individual poles in insulated cells on moderate voltage service,
and in separate tanks on high voltage; use of generously pro-
portioned high-pressure wiping and self -cleaning contacts; pro-
tection of the main contacts by arcing contacts so located that
the main current exerts a blowout effect on the arcs; use of
electric solenoid for electric operation and the use of full-auto-
matic design of latching devices, preventing the possibility of
holding the contacts in the closed position when heavy over-
loads and short circuits exist on the line.

The type H-3, H-6, and H-9 breakers of the General Electric
Company form a notable exception to some of the features
described above as their moving contacts are downward closing,
motor operated, but they embody many of the other features
and have been remarkably successful in their actual performance.

Rating. — The selection of an oil circuit breaker for application
to an electrical system or circuit requires a knowledge of the
characteristics of the breaker and the characteristics of the
system or circuit. Breakers are usually classified according to
their rated voltage, rated current, rated frequency, interrupting
capacity and instantaneous current capacity. Systems may be
classified according to their normal operating voltage, normal
current, normal frequency, and current transients.

The rated voltage of a breaker is the greatest normal
voltage as read by voltmeter in volts between any two wires
of any circuit to which the breaker should be connected.
When referred to the breaker, it is a function of its insulation
strength and of the safety factor desired. The American Institute
of Electrical Engineers has established standards for the insula-
tion strength of oil circuit breakers. All high-grade indoor
oil breakers are tested at 2% times rated voltage plus 2000
volts, and all outdoor oil breakers will stand the wet test of twice
rated voltage plus 1000 volts as specified in these rules.

Altitude. — Standard ratings of oil breakers are good for
altitudes of 3300 feet above sea level and less. For higher

OIL CIRCUIT BREAKERS 77

altitudes, standard breakers must be used on voltages less than
rated voltage, the amount of derating depending on the altitude.
For operation above 3300 feet the voltage ratings given must be
multiplied by the following factors:

Distance above Voltage rating factor

sea level, feet (G.E. Co.)

4,000 .874

6,000 .825

8,000 .775

10,000 .728

12,000 .684

14,000 .64

For applications at high altitudes, circuit breakers equipped
with special terminals can be supplied as special and should be
taken up with the manufacturing company.

The normal operating pressure of a system is the greatest
pressure in volts ordinarily maintained between any two con-
ductors.

Rated Current. — The rated current of a breaker is the greatest
current in amperes which it will carry continuously at a specified
frequency without any essential part having its temperature
raised more than a specified number of degrees above an ambient
temperature, or above a fixed temperature. The American Insti-
tute of Electrical Engineers has established heating standards
for oil circuit breakers. They limit the maximum permissible
temperature rise of coils and insulating materials of oil circuit
breakers 65 degrees Centigrade based on an ambient temperature
of 40 degrees Centigrade, and the rise of other parts whose
temperature does not affect the temperature of the insulating
material to be such as not to be injurious in other respects.
They also limit the maximum temperature of oil and contacts in
oil to 70 degrees Centigrade. For an ambient temperature of 40
degrees Centigrade, this permits a temperature rise of 30 degrees
Centigrade for oil and contacts in oil. Where, however, the
ambient temperature is less than 40 degrees Centigrade, ad-
vantage may be taken of the condition to operate the parts at
a higher temperature rise if the maximum temperatures specified
are not exceeded.

Inasmuch as a circuit breaker reaches its final temperature
quickly with steady current load, it is necessarily a maximum
rated device. On 25-cycle service a circuit breaker above 300

78 SWITCHING EQUIPMENT FOR POWER CONTROL

amperes rating will carry, continuously, considerably more than
its 60-cycle rating, and 25-cycle current ratings are therefore
given on 600 ampere breakers and above.

Interrupting Capacity. — The interrupting capacity of an oil
circuit breaker is the highest current in amperes which it will
interrupt at any specified normal pressure, frequency and duty.
This conforms with the standards adopted by the American
Institute of Electrical Engineers.

The duty on which the ampere tables have been based assumes
that the breaker will interrupt a circuit two times at a 2-minute
interval and then be in condition to be closed and carry its rated
current until it is practicable to inspect it and make any neces-
sary readjustments. This definition of interrupting capacity
selects the most common condition of oil circuit-breaker
operation.

The duty performed by a circuit breaker in interrupting the
current at a given voltage is dependent upon the current volume
and is a maximum for the largest current. Similarly, the duty
at varying voltages for a given current is increasingly more diffi-
cult at higher voltages. A given breaker equipment for any
voltage — within its rating and under proper normal adjustment —
has a certain maximum current interrupting ability. It should
not be applied to a service demanding interrupting capacity
beyond this ability.

Rating. — The proper method of rating breakers was long a
debatable question and caused a considerable amount of mis-
understanding when comparing various breakers.

A. I. E. E., 1916.— In the September, 1916, Proceedings of the
A. I. E. E. there were two papers presented, one by Mr. E. M.
Hewlett, of the General Electric Company, and the other by Mr.
S. Q. Hayes of the Westinghouse Electric & Manufacturing Com-
pany, on this subject of circuit-breaker ratings, and these papers
with the resulting discussions did a good deal to pave the way
for a more definite method of rating circuit-breaker rupturing
capacities.

A. I. E. E., 1918.— A later meeting of the A. I. E. E. in Feb-
ruary, 1918, was devoted to the consideration of a paper prepared
jointly by Mr. G. A. Burnham, of the Condit Electrical Manu-
facturing Company, Mr. E. M. Hewlett, of the General Electric
Company, and Mr. J. N. Mahoney, of the Westinghouse Electric
& Manufacturing Company. This paper contained a great deal of

OIL CIRCUIT BREAKERS

Short-Circuit Characteristics For Jhree-Pha.se Systems.
Based on Total Kva. Rating of Synchronous Machines.

RMS. Current in Terms of

Total FulkLoad Current of Machines,

Initial Full Load at a Power Factor of 80% Assumed

Q 02. 0.4 0.6 O.B ID Li 14 1.6 1.6 2.0 22 2.4 ZB 2& 3JO
FIG. 53. — Short circuit characteristics — 30 per cent, reactance or less.

Short-Circuit Charateristics For Threefhase Systems:
Based on Total Kva. Rating of Synchronous Machines.

RMS. Current inTermsor
Total-Full Load Current of Machines,
Initial Full Load at a Power Factor of 80 % Assumed

JO OZ 0.4 0£ 0.8 1.0 J2 U I.G 1.8 20 2.2 2.4 2£-2J 3JO
FIG. 54. — Short circuit characteristics — 40 per cent, reactance or more.

80 SWITCHING EQUIPMENT FOR POWER CONTROL

valuable data in the form of curves of the short-circuit condi-
tions to be met with in the average plants of different reactances
at the expiration of different lengths of time. These curves
were based on an average of a large number of curves of actual
modern generators built by the General Electric Company and
the Westinghouse Electric & Manufacturing Company, and can
be taken as representative of present American Generator
Design.

Short-circuit Curves. — These curves slightly modified for
convenience are reproduced in Figs. 53 and 54 and they show
very clearly how the short-circuit values die down very rapidly
after a small fraction of a second, and how the reactance of the
system has a great deal to do with these values.

The characteristic shapes of the time current decrement curves
have been arrived at by analysis of alternator tests including
oscillograph studies of short circuits occurring when the alter-
nators were excited to full voltage and were carrying various
loads at various power factors.

In the curves for total reactances up to and including 20 per
cent., the reactance is assumed to be wholly within the alternator
and for higher values of reactance the alternators were taken at
20 per cent, and due allowance made by calculation for the effect
of the external reactances.

The final values of the current, i.e., the sustained short-circuit
current, have been assumed in accordance with experience and
tests and are based on the behavior of machines of normal design.

The percentage reactance in any leg of a circuit is the reactance
drop in that leg of the circuit at normal current expressed as a
percentage of the voltage to the neutral of that circuit. The
percentage values are initial values based on a symmetrical sine
wave and on the maximum rating of the machines connected to
the bus. The percentage of reactance of alternators varies from
about 8 per cent, to 30 per cent. The percentage reactance of
transformers varies from about 3 per cent, to 30 per cent.

Breaker Application. — The problem of breaker application
after the service voltage has been fixed is to determine the maxi-
mum current that may be encountered, and then the breaker
should be chosen with an interrupting capacity equal to or greater
than this maximum current.

Various formulae for determining the increased rupturing
capacity to be assigned to a breaker when it is used at less than

OIL CIRCUIT BREAKERS 81

its rated voltage have been offered but it is usual to convert the
current rating into a K.V.A. rating at the listed voltage and then
allow an increase in K.V.A. rating as the voltage is lowered.

The generally accepted method of rating is to estimate an
increase in K.V.A. rating of 73^ per cent, at 75 per cent, of listed
voltage, an increase of 15 per cent, at 50 per cent, of listed voltage
and an increase of 22^ per cent, at 25 per cent, of listed voltage,
all of these figures being contingent on the fact that the current
calculated on this basis did not exceed a definite figure, deter-
mined experimentally, that expressed the maximum current
that the breaker contacts could pass for 1 second or 5 seconds
without danger of welding the contacts or causing mechanical
distortion due to magnetic forces. While these figures differ
somewhat with the details of design, they are usually given as
50 times normal for 5 seconds and in a few cases as 100 times
normal for 1 second.

The rating of a circuit breaker in current interrupted at normal
operating pressure simplifies the selection of a proper breaker for a
given service condition.

Time of Tripping. — The time delay of oil circuit-breaker
mechanisms has an appreciable effect upon the current which
they will be called upon to interrupt under transient conditions.
The contacts of ordinary oil circuit breakers part in from 0.05 to
0.40 seconds after the tripping circuit is energized, depending
on the kind of operating mechanism and tripping methods used.

The data given for the selection of oil circuit breakers is
applicable only to average systems. Therefore, a short dis-
cussion of other factors requiring separate or more detailed atten-
tion seems worth while.

Effect of Regulators. — When the alternators are equipped with
automatic voltage regulators such regulators will increase the
excitation after a short circuit in the endeavor to hold normal
voltage on the bus bars. The maximum voltage which can be
obtained from the exciters will be ordinarily not more than 50
per cent, greater than that required at full load 80 per cent,
power factor on the alternators. Under short circuit, the alter-
nator terminal voltage is reduced, hence the resultant flux density
in the alternator iron is also reduced. A given increase in
excitation, therefore, produces a proportionate increase in cur-
rent flowing in the short circuit. Hence, as can be assumed, the
excitation is increased 50 per cent., the sustained short-circuit

82 SWITCHING EQUIPMENT FOR POWER CONTROL

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Method of tripping breaker corresponding
to time elapsed

No relay A.C. series trip coil
Cur. trans, with A.C. trip coil. . .

Solenoid or motor relay Cur. trans, with A.C. trip coil. . . .
Cur. trans, with D.C. trip coil

Induction relay Cur. trans, with A.C. trip coil . . .
Cur. trans, with D.C. trip coil. . . .

Circuit breakers having A.C. or D.C. trip with definite
time setting.

OIL CIRCUIT BREAKERS 83

current will be approximately 50 per cent, greater than the
sustained current due to full-load 80 per cent, power factor
excitation.

An appreciable time, however, is required for the excitation
to increase to its maximum value. During the first half-second
the amount of short-circuit current is not affected by the presence
of the voltage regulator but from this time on the current curve
is higher, reaching the value at the end of 2 or 3 seconds
of 50 per cent, greater than the current without the regulator.

An exception to the above appears when the external reactance
is so high and the short-circuit current so limited that the regula-
tor is able to maintain normal voltage at the generator terminals.
In such cases the sustained current will be limited to the current
which will pass through the external reactance with normal
voltage impressed upon it.

Automatic Recommendations. — These are based on the as-
sumptions that the breaker is in good operating condition and
that its contacts will not part in less than the listed maximum
time after the maximum instantaneous value of the abnormal
current has been reached. Any faulty condition of the breaker,
such as poor oil, stiff bearings, sluggish operation, or accumula-
tion of dust will diminish its interrupting capacity. Also, if the
contacts part in a shorter time than the listed minimum, a
larger breaker will be required, while if the contacts part after
a greater time than the listed minimum values, a smaller breaker
may be used.

Time Relays. — These may be used to delay the parting of the
oil circuit-breaker contacts after the start of the abnormal cur-
rent. The greater the delay, the less, in general, will be the
current to be interrupted. Hence by inserting a time delay
relay, suitably adjusted, a given automatic oil circuit breaker
may be used on a larger system, or for a given system, a smaller
breaker may be used.

Short circuits in cables are not instantaneous in nature but
develop gradually into dead short circuits. On such a short,
a current may pass sufficient to actuate the breaker relay and
develop into a dead short circuit at the time the breaker con-
tacts open. Where full protection is required for such cases, a
breaker good for the initial value of short-circuit current must be
used.

84 SWITCHING EQUIPMENT FOR POWER CONTROL

Manufacturers' Guarantees. — The rupturing capacities as-
signed by manufacturers to their breakers are modified from time
to time due to improvements in design, changes in materials
employed and methods of manufacture used, but those given in
this book are those that were considered correct by the manu-
facturers at the time of publication. These are, of course, sub-
ject to change by the manufacturers.

Direct Control. — The earliest electrical power plants containing
a few machines of small output and moderate voltage were
easily controlled from switchboards where all of the switches,
meters, etc., were placed on panels. As voltage and output
increased it became necessary to utilize more space for the switch-
ing devices and to operate them either by compressed air or by
mechanical or electrical means from a central point.

Distant Control. — For the distant mechanical operation of
oil circuit breakers American practice, with its oil switches
usually designed for an up-and-down motion, favors the use of
bell cranks and rods, the latter ordinarily being a piece of standard
gas pipe screwed into suitable terminals attached to the bell
cranks, operating handles, etc. As far as possible the different
portions of the mechanical transmission are arranged in tension
for closing the breaker to avoid bending stresses, although a
reasonable amount of compression can be taken care of without
unduly increasing the weight of the mechanism.

Manual Operation. — Manual closing from a cover plate lever
or handle on a panel or frame bracket is the ordinary method of
closing small or medium sized circuit breakers both panel mount-
ing and remote control. With very large circuit breakers
manual operation becomes impossible or undesirable, owing to the
inability of a man to throw a large breaker fast enough for syn-
chronizing purposes, or even to close the circuit breakers at all
without excessive mechanical leverage, which is wasteful of
space. Stresses in manually operated remote-control parts
and the mechanical complication necessary to connect breakers
located in positions inaccessible from the switchboard or con-
trol position, often preclude the use of manually operated
remote control.

In the smaller sizes of manually operated remote-control
circuit breakers, the automatic details are mounted directly
in the cover plate, while in larger sizes the automatic latching
details are located in a special operating mechanism mounted at

OIL CIRCUIT BREAKERS 85

the circuit breaker, thus taking the strain of the latch load off the
panel and remote-control bell cranks and levers.

Where distance between switchboards and switching devices
makes the application of hand operated breakers questionable,
electrically operated breakers should be supplied.

Electric Control. — Most of this apparatus now in service is
designed for use on a 125-volt direct-current circuit, although
250, 500 or any other available direct-current voltage can be
used. In generating stations the exciter bus is sometimes the
source of the direct-current supply, but where a voltage regulator
is employed that causes the voltage of this exciter bus to fluctuate,
it is often advisable to install a small storage battery in order to
have a constant operating voltage. This battery is usually
charged from one of the exciters, a small motor-generator set,
or by using suitable resistances in series with a trolley circuit or
other direct-current circuit.

Where, for any reason, it is not desired to install a battery and
it is necessary to operate the devices from an exciter bus with
fluctuating voltage, the solenoids or motors can be designed so
that the variation in voltage will not materially change the pull
of the solenoid or the speed of the motor.

In substations for D.C. service, the breakers, etc., are often de-
signed for operation from the direct-current bus, and if the station
has been completely shut down and no direct current is available,
the first one or two breakers must be closed by hand. A small
battery can often be used to advantage in such a station and it
can be charged through a resistance from the D.C. bus. In
transformer substations a small battery charged from a motor-
generator set of about 5 K.W. capacity is nearly always installed.

A.C. Control. — From time to time it has been proposed to
operate the various devices from alternating-current circuits,
but the direct-current operation is so much cheaper and the
additional complication due to its use is so small that alternating-
current operation has made very little headway.

Indicators. — With any system of distant control apparatus, it
is necessary for the operator to know whether the different pieces
of apparatus have actually closed or opened or performed the
function assigned to them. With manual operation the auto-
matic opening of a breaker sometimes operates all of the mechan-
ism back to the handle, so no other indication is needed, but in
other cases the latch or toggle joint is at the breaker and the

86 SWITCHING EQUIPMENT FOR POWER CONTROL

position of the handle gives no clue to the position of the breaker.
For such cases or where an auxiliary source of power is used for
operating the devices some very ingenious methods of signalling
have been designed. For a breaker of any sort a mechanically
operated switch is usually provided and this switch is thrown
from one position to the other by the movement of some part of
the mechanism of the main breaker. A certain amount of
lost motion is usually provided so that unless the breaker goes
all of the way in or out the position of the signal switch is not
altered. From these signal switches circuits are run back to the
switchboard to operate signal lamps or similar devices. These
lamps are often arranged to form part of a miniature bus circuit
to show the connections that have been made by the breakers.

In the field of power operated oil circuit breakers other than
the 'H' line of G.E. oil breakers, electrical-solenoid method of
closing is now used almost universally to the exclusion of various
other methods, such as motor, hydraulic, and pneumatic power.
The electric-solenoid type of operation is very flexible and permits
mounting the operating mechanism on cell walls, or pipe frames,
or on the floor above or below, or behind the circuit breaker.

Electric operating mechanisms arfe usually provided with
combined accelerating and dashpot attachments, the former to
insure speedy opening of the contacts on tripping, the latter
to dissipate the kinetic energy of moving parts on the end of the
opening stroke. They are also usually equipped with dashpots
under the closing cores to absorb shocks of moving parts in
closing. The action of these dashpots is regulated by adjusting
screws, which determine the extent of the valve opening.

Control Circuit. — Standard electric operating (closing and
tripping) mechanisms are made for direct-current operation.
This form, besides utilizing simpler construction, being more
reliable in operation, and more easily kept in repair, is much more
economical of space and power than alternating-current mechan-
isms. For special applications, such as for alternating-current
electrically operated railway sectionalizing circuit breakers and
other installations where no auxiliary source of direct-current
power is available, special alternating-current operating mechan-
isms can be supplied.

Mechanism. — The standard electric mechanism closes the
breaker by a direct-current magnet and holds it closed by a
latch and trigger or a toggle, which engage automatically. The

OIL CIRCUIT BREAKERS 87

tripping mechanism consists of a direct-current trip magnet
acting on a trigger which releases the latch, permitting the
breaker to open.

The closing and tripping mechanism is operated by a control
switch, with or without control relays (switches) in the closing
circuit, and usually with signal lamps.

All electric operating mechanisms have a small double-throw
switch to open the shunt-trip coil circuit when the circuit breaker
opens and to operate the signal lamps.

Control Voltage. — The standard electric mechanisms are
regularly supplied with closing solenoids wound for 70 to 140
volts (110 volts nominal) direct current. The time required to
close a breaker from the time of the closing of the control switch
contacts until the arcing contacts in the breaker touch, is %o
to % o seconds. Coils for other than the aforementioned stand-
ard voltages, or of greater operating range, can be supplied.

The electric mechanisms are equipped with tripping as stand-
ard, to operate at from 50 to 140 volts direct current.

Electric operating mechanisms can be furnished with closing
coils to operate at from 140 to 280 volts, direct current, or to
trip at from 100 to 280 volts, direct current.

Acceleration. — One of the prime necessities in oil circuit-
breaker operation is that when the contacts have commenced to
separate they shall travel rapidly, especially during the first part
of the stroke. Speed of operation reduces the duration of the
arc, reduces the amount of energy expended in the arc, reduces the
volatilization of metal parts and oil, and, consequently, reduces
the tank pressure which is a determining factor in the ultimate
capacity rating of a breaker. All small automatic circuit
breakers are provided with accelerating springs in the contacts
themselves, which insures speedy operation when the switch
is unlatched. Automatic overload-trip remote-control circuit
breakers in smaller sizes are provided with accelerating devices
mounted on one of the remote-control bell cranks. This device
precludes any possibility of the sticking of the circuit breakers,
when tripped, in case the system of remote-control rods and
cranks is arranged so that they over balance the weight of the
circuit breaker contacts; it also insures a rate of acceleration of
moving parts greater than that due to unassisted gravity.
Where the weight of the moving contact parts is large and
there would be danger of breakage if they were suddenly ar-

88 SWITCHING EQUIPMENT FOR POWER CONTROL

rested, the device is equipped with means of stopping the
moving contact.

The beneficial effect on the operation of a circuit breaker
by this accelerating device is such that a remote-control circuit
breaker often can be rated at a higher breaking capacity than
the corresponding panel mounting circuit breaker.

METHODS OF TRIPPING

Non-automatic Trip. — Manually operated circuit breakers,
supplied for non-automatic operation, are tripped by hand from
the faceplate or breaker mechanism. Electrically operated
circuit breakers supplied for non-automatic operation are sup-
plied with a direct-current shunt-tripping magnet acting on a
trigger that releases the latch. The shunt-tripping magnet is
usually energized by a circuit controlled from some central point,
or it may be connected to a relay circuit, thus giving automatic
features through the relays.

When direct current is not available for operating the standard
shunt tripping magnet, special magnets can usually be supplied
for using alternating current.

Automatic Overload Trip. — Plain-automatic overload-trip cir-
cuit breakers when closed with an overload on the line will remain
closed as long as the closing coil (of electrically operated breakers)
is energized, or the manually operated mechanism is held in the
closed position. With electrically operated breakers, when the
closing coil circuit is opened, the breaker will not remain closed
on overloads. Electrically operated circuit breakers, only, are
regularly supplied plain automatic.

Full Automatic. — Full-automatic overload-trip circuit breakers
have a mechanism making it impossible to hold the breaker in a
closed position while a continuous overload condition or short
circuit exists on the circuit.

Transformer Trip. — For manually operated circuit breakers
direct tripping from the secondary of current transformers is the
most common method of automatic overload tripping where no
time element feature is necessary. For some low voltage indoor
circuit breakers, series trip overload coils can be used, mounted
directly on the circuit breaker.

Where time limit features are wanted, inverse time limit dash-
pots are supplied on some types of circuit breakers, or relays
having this feature may be used.

OIL CIRCUIT BREAKERS 89

For electrically operated circuit breakers, tripping from the
secondary of current transformers is most common. This
tripping can be accomplished by connecting the secondaries
directly to the current trip coils of the circuit breaker, or by con-
necting them to relays which operate the current trip coils or
shunt-trip coils. Series automatic overload-trip coils can also be
used on some electrically operated circuit breakers.

The coils for current transformer automatic overload trip are
mounted in the cover plate or on the breaker mechanism of the
manually operated circuit breakers, and on the operating mechan-
ism of electrically operated circuit breakers.

Ordinarily, where current transformers are used for instru-
ments and watt-hour meters the trip coils can be connected to
the same transformers, if great accuracy is not required. Where
not required for instruments or meters, lower priced transformers
of good accuracy are available for connection directly to the
circuit-breaker trip coils or to relays.

Series Trip. — The coils for series automatic overload trip are
either dry insulated, mounted in the switchboard cover plate, or
they are contained in the circuit-breaker oil tank. In the former
case, the main connections to the series trip coils are made
through holes in the panel, these holes being covered by the
cover plate. This method of trip is recommended to be applied
only to .small low capacity installations not having current
transformers for meters.

Tripping Calibration. — Breakers automatically operated from
current transformers and current transformer trip coils or from
series trip coils are usually calibrated to function through a
range of from 80 to 160 per cent, of the normal current rating of
the current transformer or of the series trip coil. The tripping
coils can be set to function at any current within the range given
on the scale. Since the transformer trip coils are energized by
power from the secondaries of series transformers in the main
circuit, the high voltage is removed from the cover plate and,
therefore, from the front of the switchboard panel or other
operating station.

Inverse Time. — When inverse time limit is required to prevent
the circuit breaker coming out unnecessarily on short overloads,
an adjustable inverse time limit dashpot can be applied to the
standard cover plate of some breakers, With various mixtures
of oil, the time limit can be varied considerably.

90 SWITCHING EQUIPMENT FOR POWER CONTROL

Where automatic undervoltage protection is required or
where tripping is desired upon failure of power rather than from
an auxiliary circuit, an automatic undervoltage trip can be
supplied. Up to 600 volts alternating current the coil of this
attachment is shunted directly across the line but on higher
voltages the coil is connected in the secondary of a voltage
transformer.

The automatic undervoltage-trip attachment, as described
above, can be supplied with a 5-ampere coil and then used as an
automatic underload-trip device in connection with appropriate
current transformers to trip the circuit breakers upon the load
decreasing below a predetermined amount. These are of the
manual reset form.

Automatic overvoltage-trip coils can be used on circuit
breakers to trip the breaker in case the voltage of the circuit
increases to a certain predetermined setting.

CONDIT OIL CIRCUIT BREAKERS

A very complete line of oil circuit breakers has been put on the
market by the Condit Electrical Manufacturing Company, of
South Boston, ranging in size from the types G> I and N
for industrial service and motor starting, the M for manhole
and P for pole top through the various switchboard types
E and D to the large capacity separately mounted breakers
for compartment mounting and the outdoor high tension
breakers.

Motor Starters. — The type G-l oil motor starters are used
for starting squirrel-cage motors that do not need any auto
starter or compensators. These are essentially double-throw
breakers for currents up to 100 amperes for motors up to 35
H.P. In the starting position the overload coils are not in circuit
but as soon as the motor gets up to speed the breaker is thrown
over to the running position when the automatic coils are cut in
and time limit devices prevents a momentary current surge from
tripping out the breaker.

The type I motor starters are somewhat similar but in place
of overload coils the automatic protection is secured through
fuses that are cut out at starting but in circuit during the run-
ning position. These are used for motors up to 10 H.P. at 440
and 550 volts.

The N-l oil starter is suitable for circuits with starting

OIL CIRCUIT BREAKERS 91

currents up to 150 amperes at 110 volts, 80 amperes at 550 volts.
Its general features correspond with the G-l.

Entrance Switches. — The N-2 oil circuit breakers are in-
tended principally as entrance switches for a maximum current
of 60 amperes and maximum voltage of 600. The case is divided
into three parts: the top contains the fuses; the middle carries
the switch mechanism; the bottom forms the oil tank. While
this is a non-automatic device with or without fuse clips it can be
provided with shunt-trip or undervoltage release.

Manhole Switches. — For manhole service the M-5 is
furnished both single throw and double throw with cable sleeves
for single conductor cable and the M-6 is furnished for single
throw only and for multiple conductor cables. The design of
the operating mechanism of the M-5 and M-6 oil switches em-
bodies the highly important feature of easy closure, and at the
same time affords ample pressure at the contact surface. It is
extremely simple in design and positive in action. The bearings
are made of non-corrosive metal. The handle not only operates
the switch, but, being removable, also serves to insert and remove
the plug which seals the switch. Each brush or bridging member
is built of special hard-drawn copper laminae, so formed that each
lamina makes individual contact with the stationary contact
member and allows a definite space for the free circulation of
oil between adjacent laminae. The brushes make contact with
a long-wiping, self -cleaning action. They are secured to specially
treated wood rods in such a manner that they are self-aligning,
insuring each individual lamina carrying its full share of the cur-
rent. This construction gives the laminated brush decidedly
excellent current-carrying features. Each brush is protected by
two auxiliary arcing tips made of relatively heavy, special
shaped, hard-drawn copper. They are mounted on the extremi-
ties of a spring support fastened to the lower portion of the brush
so as to make contact with similar stationary arcing tips fas-
tened to the stationary contact member. Each of these arcing
tips is easily renewable and reversible, giving approximately
twice the usual length of service, and decreases the maintenance
cost of the switch correspondingly.

Pole Switches. — Pole line oil switches, type PK-5, are for
weatherproof service and are used for the sectionalizing of lines,
switching of transformer banks and similar service. They are
suitable for use on alternating-current circuits where the

92 SWITCHING EQUIPMENT FOR POWER CONTROL

current does not exceed 200 amperes at pressure of 4500 volts
or less.

The mechanism is extremely simple in construction and is
enclosed in a substantial weatherproof iron case. The cover is
provided with an overhanging rim, securely fastened by swinging
bolts and wing nuts, permitting easy access to the interior. A
depending projection on the front of the cover serves as an effi-
cient watershed for the operating handle and prevents the forma-
tion of ice and sleet from interfering with the operation of the
switch.

The oil tank is made of heavy sheet metal with welded joints,
combining strength and rigidity, and is fastened to the frame by
means of swinging bolt and wing-nut construction, thus allowing
the tank to be readily removed without disturbing any of the
operating parts.

The tank is provided with a suitable lining, and barriers are
interposed between the poles to give additional protection against
arcing under severe conditions.

Single-tank Breakers. — The E line of breakers is distin-
guished by having all poles of the breaker in the same tank.
The E-3 breakers are arranged for panel mounting, panel frame
mounting or remote control by hand or solenoid. Series trip
coils or current transformer trip can be used and a rupturing
capacity of 1600 amperes at 4500 volts, 3300 at 2500 can be
guaranteed.

Type E-3. — Condit type E-3 oil circuit breakers, Fig. 55, have
been designed primarily for controlling and protecting feeder
circuits, transformer banks, generators, etc., where moderate
interrupting capacity is required. They are made in two,
three and four poles, single and double throw, automatic and
non-automatic, for manual and electrical operation. All of the
automatic forms may be provided with undervoltage, shunt-
trip and time limit attachments. Auxiliary switches of the
circuit opening and circuit closing type may also be utilized in
connection with either the non-automatic or automatic form.

The automatic form may be furnished in either series,current
transformer, or relay trip. Type E-3 series trip oil breakers have
a maximum capacity of 200 amperes, and may be used where the
pressure does not exceed 2500 volts.

Non-automatic and current transformer or relay trip oil circuit
breakers are furnished in capacities up to and including 300

OIL CIRCUIT BREAKERS

amperes, and may be used where the pressure does not exceed
4500 volts. They are furnished for panel, panel frame or pipe
frame mounting for direct control, and are arranged for flat
surface or pipe frame mounting for manual remote control or
electrical remote control. Double-throw switches and circuit
breakers are arranged for panel mounting only.

FIG. 55. — Condit Electric & Mfg. Co. oil circuit breaker, type E3, single throw.

All automatic type E-3 overload circuit breakers have their
trip coils and calibration adjustments on the front of the switch-
board, and the mechanism is arranged to prevent the operator
from holding the switch closed during an overload or short
circuit. The mechanism is capable of adjustment to suit the
conditions of installation.

Studs. — The studs are copper rod of sufficient cross-section
to properly carry their rated current continuously, and are
insulated from the frame by high-grade, well-glazed porcelain
bushings, thus affording ample insulation. The top of the stud

SWITCHING EQUIPMENT FOR POWER CONTROL

is threaded to receive the terminal to which line conductors may
be connected. Fastened to the lower end is a stationary contact
member on which is mounted the stationary arcing tips.

The terminals are enclosed in an insulating sleeve in order to
prevent accidental contact with the live parts.

Tank. — The oil tank is made of heavy sheet metal with welded
joints, combining strength and rigidity. The tank fits inside of
an overhanging rib which forms a part of the cover or frame of the
breaker. This rib construction materially reinforces the tank
and prevents its sides from bulging outwards, even when sub-
jected to excessive pressure from within. It is fastened to the
cover or frame by means of heavy tank bolts and wing nuts,

thus allowing the tank to be
readily removed for inspec-
tion, without disturbing any
of the operating parts. The
tank is provided with a suit-
able lining and barriers are
supplied between the poles to
give additional protection
against arcing under severe
conditions. An oil line on
the outside of the tank indi-
cates the height to which the
tank should be filled with oil
when removed from the
breaker.

Type E-4.— Fig. 56 shows
the arrangement of the panel
mounting, double-throw
breaker, with the two inter-
locked closing handles. These
type E-4 breakers are made in capacities of 300 and 500 amperes
at 7500 volts and 800 at 4500 for rupturing capacities of 1700
amperes at 7500 volts for the 300 and 500 ampere sizes, 3160 at
4500 for all sizes, 6100 at 2500 for all sizes, and 15,000 for the
300 and 500 at 750, and 20,000 at 750 for the 300 ampere size.
Their general features correspond closely with those described
for the E-3.

All automatic type E-4 overload circuit breakers have their
trip coils and calibration adjustments on the front of the switch-

FIG. 56. — Condit Electric & Mfg. Co.
oil circuit breaker, type E4, double
throw.

OIL CIRCUIT BREAKERS

board, and the mechanism is arranged to prevent the operator
from holding the switch closed during an overload or short
circuit.

Fig. 57 shows the arrangement of the 800-ampere 4500-volt
type E-4 breaker hand operated, remote control.

Fia. 57. — Condit Electric & Mfg. Co. oil circuit breaker, type E4, hand operated,
remote control.

Motor Starters. — The type E-6 oil starter is a combination of a
switch and a circuit breaker, used for controlling and protecting
induction and self -starting synchronous motors whose continuous
full-load current, including overloads, does not exceed 200 am
peres at pressures of 2500 volts or less.

They are used extensively for starting squirrel-cage induction
motors without the use of auto transformers or compensators.

96 SWITCHING EQUIPMENT FOR POWER CONTROL

Three-pole switching equipment is furnished for use with 3-phase
or 3-wire, 2-phase induction motors, and 4-pole switching equip-
ment is furnished for use with 2-phase motors supplied from
4-wire, 2-phase, non-interconnected systems. Type E-6 oil
starters are made 3 or 4-pole, manually operated, panel mount-
ing only, arranged for series or current transformer trip with
time limit attachments and selective mechanical interlock.
They may also be provided with under- voltage and shunt-trip
attachments.

The faceplate is provided with two handles. The handle on
the left operates the starting switch and cannot be latched closed.
The handle on the right operates the circuit breaker which pro-
tects the motor, when running, from short circuit, overload, and
single phase running.

The trip coils and calibration adjustments are conveniently
located on the front of the panel.

Type E-7. — The type E-7 oil starter is a combination of a
switch and a circuit breaker, used for controlling 3-phase
induction or self-starting synchronous motors whose continuous
full-load current, including overloads, does not exceed 200 am-
peres at pressures of 2500 volts or less. These oil starters are
arranged only for 3-wire, 3-phase, and 3-wire, 2 phase, alternating
current motors. They are not suitable for use on 4-wire, 2 phase,
non-interconnected systems. They may be used in connection
with auto transformers having either 2 or 3 exciting coils, and
are made 4-pole, manually operated, panel mounting only,
arranged for series or current transformer trip with time limit
attachments and selective mechanical interlock. They may also
be provided with undervoltage and shunt-trip attachments.

The faceplate is provided with two handles. The handle on
the left operates the starting switch and cannot be latched
closed. The handle on the right operates the circuit breaker
which affords protection against short circuit, overload and single-
phase running.

Independent Tank Breakers. — Type D-12 circuit breakers
have independent tanks for each pole of the breaker but all
poles on the same frame. These breakers have a guaranteed
rupturing capacity of 1250 amperes at 15,000 volts; 2500 at
7500; 4200 at 4500, and 7500 at 2500 volts. The 300, 500 and
800 amperes at 2500 volts are made for panel frame mounting
and all of the other ratings for distant control only. They are

OIL CIRCUIT BREAKERS

used to meet the demands in controlling and protecting electrical
circuits and apparatus where the pressure does not exceed 15,000
volts. They are well adapted for installations where space
requirements are an important factor, and a relatively high
interrupting capacity is desired. They are used principally to
control feeder circuits in substations of large distribution systems

FIG. 58. — Condit Electric & Mfg. Co. oil circuit breaker, type D12, frame
mounted.

and for the control and protection of generators and feeders in
industrial service where a relatively high rupturing capacity is
required at moderate voltages.

All automatic type D-12 overload circuit breakers have their
trip coils and calibration adjustments on the front of the switch-
board, and the mechanism is arranged to prevent the operator
from holding the switch closed during an overload or short
circuit. They are furnished for current transformer trip or non-

98 SWITCHING EQUIPMENT FOR POWER CONTROL

automatic, as panel frame mounting shown in Fig. 58, 2500 volts
or less where the current does not exceed 800 amperes. For
flat surface (wall or cell mounting) or for pipe frame mounting,
they can be supplied manually operated remote control and elec-
trically operated for 4500 volts or less where the current does not
exceed 1200 amperes; 7500 volts or less where the current does
not exceed 1000 amperes; 15,000 volts or less where the current
does not exceed 800 amperes.

Electrically operated. — This type of D-12 oil circuit breakers,
Fig. 59 is furnished in the standard ampere capacities, poles,
and mountings at the various voltages. They consist of the

FIG. 59. — Condit Electric & Mfg. Co. oil circuit breaker, type D12, solenoid
operated, 1200 amps.

standard manually operated breaker equipped with a closing
magnet, opening magnet, control relay, control switch with red
and green indicating lamps, and one indicating lamp switch.

Terminals up to and including 800 amperes are enclosed in an
insulating sleeve to prevent accidental contact with live parts.
Circuit breakers in excess of 800 amperes are provided with
laminated terminals to which cable terminals or flat copper
connections may be bolted.

Each pole of the D-12 oil circuit breakers is provided with an
individual oil tank made of 3^-inch steel with welded seams, and
is provided with a suitable lining. Each tank is fastened to the
frame by a strong tank bolt construction, which allows ready

OIL CIRCUIT BREAKERS

removal for inspection without disturbing any of the operating
parts.

A depending flange, which serves to strengthen the frame,
prevents any tendency to tank distortion when circuit breakers
are called upon to interrupt the circuit under severe conditions.
An oil line on the outside of each tank indicates the height to
which the tank should be filled with oil when removed from the
breaker.

FIG. 60. — Condit Electric & Mfg. Co. oil circuit breaker, type D13, hand
operated, remote control.

Type D-13. — The D-13 oil circuit breakers have a guaranteed
rupturing capacity of 1000 amperes at 25,000 volts for the 300
and 500 ampere sizes; 1700 at 15,000, 3500 at 7500, 5800 at
4500, and 10,000 at 2500 for all sizes. They are made in single,
2-, 3-, and 4-poles, for manual remote control or electrical
operation with separate tanks per pole. They are furnished

100 SWITCHING EQUIPMENT FOR POWER CONTROL

in 300, 500 and 800-ampere capacity for pressures of 15,000 volts
or less, and for capacities of 300 and 500 amperes where the
pressure does not exceed 25,000 volts. This type is adapted for
flat surface mounting on either walls or in cells, or it may be
mounted on pipe frame structures.

Mechanism. — Each pole of the D-13 oil circuit breakers,
Fig. 60, is provided with an operating mechanism of unique
design. The upper extremity of the brush rod is provided with
a threaded ferrule fastened so as to give maximum mechanical
strength. The ferrule and rod are threaded into a pivoted
cross-head at the end of the operating mechanism which travels
with a straight-line motion. This construction serves as a
brush adjustment and maintains the brush rigidly in its proper
position in relation to the stationary contact members. The
brush is fastened in a self-aligning manner to the lower extremity
of the brush rod.

The mechanism closes easily and at the same time affords
ample pressure at the contact surface. It is designed particu-
larly to allow rapid acceleration of the movable contact
members during the initial opening of the circuit. Each of the
individual poles is operated through a common shaft, which
may be actuated either manually or electrically.

Attachments. — Undervoltage attachments for D-12 and D-13
breakers are designed so that the breakers will be released when
the pressure drops to approximately 50 per cent, of its normal
value. Shunt-trip attachments are provided with a heavy
tripping spring, which insures positive action. They are wound
for voltages of 110, 220, 440, and 550, for either direct or alter-
nating current, 25 or 60 cycles, and have an operating range from
55 to 115 per cent, normal voltage.

Many forms of devices, such as relays and time limit attach-
ments, may be used in conjunction with type D-12 oil circuit
breakers for the purpose of causing their operation in accordance
with predetermined conditions. Type D-12 oil circuit breakers
may be furnished with time limit attachments applied directly to
the calibration tubes, in capacities up to and including 800 am-
peres. Time limit attachments are not furnished for 1000 am-
peres and above.

Heavy-current Types. — Type Y-l and Y-2 oil circuit breakers
are used on circuits of moderate voltage and relatively large
ampere capacity, for the control and protection of generators,

OIL CIRCUIT BREAKERS 101

FIG. 61.— Condit Electric & Mfg. Co. oil circuit breaker, type Yl.

FIG. 62. — Condit Electric & Mfg. Co. oil circuit breaker, type Y2.

102 SWITCHING EQUIPMENT FOR POWER CONTROL

motors, transformer banks, feeder-circuits, as service entrance
switches, etc.

Type Y-l. — These oil circuit breakers as shown in Fig. 61 are
made 3 and 4-pole, automatic and non-automatic, for manual
remote- control and electrical remote-control operation. All of
the automatic forms may be provided with undervoltage and
shunt trip. They are furnished for use on circuits where the
pressure does not exceed 2500 volts and the current does not
exceed 2500 amperes at 60 cycles, or 3000 amperes at 25 cycles.

Type Y-2. — These oil circuit breakers, Fig. 62, are made 3-pole
only, for use on circuits where the pressure does not exceed 2500
volts, and where the maximum capacity does not exceed 4500
amperes at 60 cycles, or 5500 amperes at 25 cycles. Auxiliary
switches of the circuit opening and circuit closing type may be
utilized in connection with either the automatic or non-automatic
forms.

Ratings. — The Y-l breakers are made in 25-cycle ratings of
1800, 2400 and 3000, amperes with corresponding 60-cycle ra-
tings of 1500, 2000, and 2500. The Y-2 breaker has a 60-cycle
rating of 4500 amperes and a 25-cycle rating of 5500. The
guaranteed rupturing capacities of the Y-l are 7500 amperes at
2500 volts, 30,000 at 750, while for the Y-2 the rupturing capaci-
ties are 15,000 at 2500 volts, 50,000 at 750.

Each pole of the type Y oil circuit breakers is provided with an
individual steel oil tank with welded seams. Each tank is
fastened to the frame by a strong tank bolt construction which
allows ready removal for inspection without disturbing any of
the operating parts.

A rugged, box-shaped frame carries the operating mechanism,
to which is securely fastened a heavily ribbed, non-magnetic
metal cover which serves as a support for the insulating bush-
ings, studs and oil tanks.

Brushes. — Each brush or bridging member, shown in Fig. 63 is
built up of special hard-drawn copper laminae, so formed that each
lamina makes individual contact with the stationary contact
member and allows a definite space for the free circulation of oil
between adjacent laminse. The brushes make contact with a
long-wiping, self -cleaning action. Each brush is suspended by an
individual, specially treated wood rod, in such a manner that the
brushes are self-aligning in relation to the stationary contact
members. This construction permits of easy and convenient

OIL CIRCUIT BREAKERS 103

individual brush adjustment, without the use of shims — a feature
of great importance in apparatus for this class of equipment.

The studs are insulated from the supporting frame by moulded
insulation designed particularly to withstand mechanical strains
incident to the operation and installation of oil circuit breakers
of large ampere capacity. The studs are made up of laminated
copper bars, each 4-inch by ^-inch, the number depending upon
the ampere capacity. The top of the stud is arranged to receive
3^-inch bar connections or cable terminals to receive the line
conductors. Fastened to the lower end of the stud is the sta-
tionary contact member on which are mounted the stationary
arcing tips.

FIG. 63. — Condit Electric & Mfg. Co. brush construction type "Y2" oil current
breaker.

Each brush unit is protected by two extra heavy, special-
shaped auxiliary arcing tips made of hard-drawn copper. They
are mounted on the extremities of a spring support fastened to the
lower portion of the brush, so as to make contact with similar
stationary arcing tips. Each of these arcing tips is easily re-
newable and reversible, giving approximately twice the usual
length of service and decreasing the maintenance cost corre-
spondingly.

Cell Mounting. — The type F-6 oil circuit breakers, Fig. 64,
are furnished 3-pole only, cell mounting, in 500 and 800 ampere
capacities where the pressure does not exceed 15,000 volts. They
may be arranged for either hand remote control or electrical
operation and embody distinctive features which make them
highly desirable for installations where continuity of service is
essential.

Construction. — The renewable unit construction is employed
in connection with the type F-6 oil circuit breaker, as this renders
the quickest possible means of replacement, repair or inspection.
The operating mechanism is entirely enclosed in the expansion

104 SWITCHING EQUIPMENT FOR POWER CONTROL

chamber, which is firmly fastened to a 34-inch steel tank
supported on a three-point truck to facilitate easy handling.
The electrically operated mechanism is compact, of simple
design, and is mounted above the switch units. The conductors
may be brought to the circuit breaker either through the top or
rear of the cell.

FIG. 64. — Condit Electric & Mfg. Co. oil circuit breaker, type F6.

The important features of design which characterize the type F-6
oil circuit breakers are the efficient laminated brush, reversible
and easily renewable arcing tips, self-aligning, sure seating
action between the movable contact members and the station-
ary contact members, the rugged tank-per-pole construction,

OIL CIRCUIT BREAKERS

105

FIG. 65. — Condit Electric & Mfg. Co. oil circuit breaker, type D15 floor
mounting.

FIG. 66. — Condit Electric & Mfg. Co. oil circuit breaker, type D15, frame
mounting.

106 SWITCHING EQUIPMENT FOR POWER CONTROL

high head of oil over break, large expansion chamber and the
strong spring action inherent in the brushes which facilitates
rapid acceleration of the movable contact members on the initial
opening of the circuit.

High Voltage Breakers. — Type D-15 oil circuit breakers are
furnished for indoor application for the control and protection
of transmission lines, transformer banks, etc., where the normal
operating voltage is 44,000 volts or less. The type R-l oil cir-
cuit breakers are used where the normal operating voltage is
70,000 volts or less. For outdoor application, type D-16 oil
circuit breakers are furnished.

Type D-15. — These -oil circuit breakers are made 3-pole
only, arranged for manual direct control, manual remote control
or electrical remote control. They are furnished in the following
standard ampere capacities: 300 amperes, 44,000 volts or less;
300, 500 and 800 amperes, 25,000 volts or less. They are made
in two forms of mounting: floor mounting, where the tanks rest
on the floor, as shown on Fig. 65 and frame mounting, as shown
on Fig. 66.

They consist essentially of three separate, identical units,
sufficiently spaced so that cell walls and barriers are usually un-
necessary. Each unit consists of a strong, well ribbed cover,
forming a large expansion dome. This cover supports the me-
chanism and conducting parts. The oil tank is securely fastened
to the expansion dome, and is provided with an oil gauge and
oil drain.

The D-15 oil circuit breakers are characterized by the laminated
brush, reversible and easily renewable arcing tips, the rugged
tank construction, large expansion chamber, and the strong spring
action of the brushes which facilitates rapid acceleration of the
moving contact members upon the initial opening of the circuit.
They are furnished for current transformer and relay trip.

Type D-16. — These oil circuit breakers are furnished for
outdoor application for the control and protection of transmission
lines, transformer banks, etc., where the normal operating volt-
age is 44,000 volts or less. They are made 3-pole only,
arranged for manual direct control or electrical remote control
and are furnished in the following ampere capacities : 300 amperes
44,000 volts or less; 300, 500 and 800 amperes, 25,000 volts or less.

The D-16 oil circuit breakers are made in two forms of mount-
ing : floor mounting, where the tanks rest on the floor, and frame

OIL CIRCUIT BREAKERS

107

mounting, Fig. 67, where the tanks are supported by a frame
structure. They consist essentially of three separate, identical
units, so arranged with relation to a common operating mechan-
ism as to cause simultaneous operation of the contact members.
Each unit consists of a strong, well ribbed cover, forming a large
expansion dome. This cover supports the mechanism, bushings
and weatherproof hood. The oil tank is securely fastened to

FIG. 67. — Condit Electric & Mfg. Co. oil circuit breaker, type D16, frame
mounting.

the expansion dome and is provided with an oil gauge and oil
drain. These oil circuit breakers are characterized by large
expansion chamber with baffled gas vents, substantial tank
construction, reversible and easily renewable arcing tips, and
efficient laminated brush, the strong spring action of which
facilitates rapid acceleration of the moving contact members upon
the initial opening of the circuit.

108 SWITCHING EQUIPMENT FOR POWER CONTROL

GENERAL ELECTRIC OIL BREAKERS

The General Electric Company early advocated the use
of the oil circuit breaker for A.C. service and have done a great
deal of pioneer work in developing breakers suitable for various
classes of service. Their earlier designs have naturally been
superseded by later modifications embodying the improvements
that experience has shown to be advantageous.

Lines. — There are a number of different lines of breakers to
take care of the different classes of work. For the small in-
dustrial service, there are the TP-10' and similar breakers;
for the moderate capacity moderate voltage breakers for switch-
board service the 'K-5' and 'K-12' breakers are being super-
seded by the 'K-32' and 'K-35,' while for moderate voltages
and high rupturing capacity the 'H-3,' 'H-6,' and 'H-9'
breakers are utilized and the high voltage circuits are taken care
of by the 'K-24,' 'K-26,' <K-36/ etc.

Industrial. — For industrial service the TP-10' breaker is
built in capacities up to 50 amperes for 600 volts, is arranged
for conduit wiring and is suitable for induction motors up to
25 H.P.

The automatic breaker is provided with two series inverse
time overload trip coils, mounted inside the cover. Dashpots and
calibrating tubes are covered by a drawn steel casing attached
to breaker frame. The breaker cannot be held closed on overload
or short circuit. The undervoltage breaker can be furnished
triple or four-pole with a self-setting undervoltage release attach-
ment mounted inside the breaker frame which trips the breaker
if the voltage of the line drops to approximately 50 per cent, of
normal.

The non-automatic breaker is similar to undervoltage and
overload forms except there is no tripping attachment and operat-
ing mechanism is slightly different.

The combined overload and undervoltage breaker is made
triple-pole with undervoltage release and overload protective
plugs; four-pole with undervoltage release and double-series
overload trip. Both protective plugs and series coils with time
delay provide protection to motor when starting. Four-pole
breaker is used triple-pole by omitting connections to one set of
contacts.

The cover is a single piece of sheet steel and fits tightly over the
top of the breaker frame which is a light but strong sheet-steel

OIL CIRCUIT BREAKERS 109

box which supports all parts of the breaker. The words "off"
and "on" on the frame indicate whether the breaker is open or
closed. Oil dashpots give time delay to automatic overload
trip which can be set to remain inactive on starting current of
motor but to trip out breaker on sustained overloads, including
those caused by single-phase operation.

The operating handle is the only movable part of breaker
not enclosed. On opening this form of breaker manually, the
handle is moved some distance to the left before the contacts
begin to part, after which they are snapped quickly open by a
torsion spring on the operating shaft.

The fixed contacts are copper fingers flared at lower end to
form arcing tips. Contact studs are securely held in a porcelain
block.

The movable contacts are mounted in a porcelain block, and
consist of copper strips bent to form. The arc, on opening
breaker under load, is confined to the stationary arcing tips and
upper ends of movable contacts, and does not affect the working
contact surfaces. Contacts are always kept clean and will last
a long time even under rough usage.

All combinations, both automatic and non-automatic, except
the triple-pole, plain undervoltage breaker and the combined
undervoltage, protective plug breaker can be furnished either
with the quick break, or quick make and quick break mechanism.
Quick break is a feature of all these breakers. Breakers with
both quick make and quick break mechanism are especially
adapted for shipper rod operation.

Textile. — A modification of this breaker known as the 'FP-
15' is made for non-automatic service, particularly for motors on
textile machinery, and the operation is either manually or by
shipper rod. They can be used to great advantage to replace
knife switches as their safety features make the breaker dust-
proof and fireproof as well as guarding the operator.

Pole Line. — For pole line service the TP-7' is intended for
mounting on any vertical flat surface and is supported on the side
opposite the operating handle. The frame is a cast-iron box
which supports all parts of switch and is provided with a cast-
iron cover fastened to frame by four eye bolts with wing nuts.
Porcelain entrance bushings are used for all cables entering the
switch. The fixed contacts are drop-forged copper fingers
flared at lower end to form arcing tips while the movable contact

110 SWITCHING EQUIPMENT FOR POWER CONTROL

blades are wedge-shaped, which confines arc to top edge of blade
and flared portion of contact fingers. The oil vessel is made of
heavy sheet metal lined with laminated wood and barriers of
same material between poles.

Old K-5 and K-12. — Some of the older designs of type 'FE-
S' and 'FK-12' were built with insulators suitable for 15,000
volt service for the 500-ampere size, this being modified by using
shorter porcelains with extension pieces under the oil to utilize
the same moving parts and to secure the same depth of oil over
the contacts for 2500-volt service, and for 600-volt service. The
rupturing capacities assigned to the
FK-5 for their various voltages were
1700 at 7500, 2600 at 4500, 5300
at 2500 and 15,000 at 600 volts.

The contacts for these breakers
are usually made with flared copper
fingers supported by heavy steel
springs. The movable contacts had
wedge-shaped copper blades slotted
at the apex in such a way that oil is
forced through the slots into the arc.
Modifications of this breaker with
independent poles placed in masonry
compartments were used for large
capacities and high voltages.

Modern Types. — The more mod-
ern types of FK-12 breakers are
built in capacities of 300, 500, and
800 amperes with a single blade
contact, while the FK-12B is made
with a single blade for 1000 amperes
1200 and 1500 amperes, the latter

FIG. 68. — General Electric Co. oil
circuit breaker type "FK12."

and with double blades for
arrangement being shown in Fig. 68.

The frame is a single metal casting, supporting all of the
breaker parts. Suspended from it is the oil tank of heavy sheet
metal with welded joints. The oil tanks of single-pole breakers
are lined with fibre and those of the multipole breakers with
treated laminated wood. Multipole breakers have barriers of
the same special wood between poles.

The operating mechanism, carried on the frame, is designed to
produce parallel movement of the blades with the breaker opening

OIL CIRCUIT BREAKERS 111

by gravity assisted by the springs on the contact fingers and on
the mechanism. The operating rods attached to the mechanism
are made of specially treated wood, screwed and clamped into
the crosshead and into the movable contact blade. This blade
is wedge-shaped, confining the arc to the top of the blade and
protecting the actual contact surface from the damaging effect
of the arc.

The fixed contacts are drop-forged copper fingers secured to
the blocks at the lower end of the terminal studs. The fingers
are flared at the tips and one set is extended to act as arcing tips.
These contact studs and clip blocks are of one-piece solid drop-
forged copper, placed in bushings of one-piece glazed porcelain
extending below the level of the oil. The bushing clamps are
interchangeable metal plates with trued surfaces which firmly
secure the insulator to the frame in proper alignment.

Ratings. — The rupturing capacities assigned to the FK-12
and FK-12-B breakers built for various voltages are 700 amperes,
at 22,000 volts, 1200 at 15,000, 2760 at 7500, 4840 at 4500,
9000 at 2500 and 30,000 amperes at 750 volts.

Type K-32.— These FK-12 and FK-12-B breakers are being
superseded by the FK-32-A and FK-32-B standard unit designs
that can be assembled as single, double, triple, or four-pole com-
binations. Fig. 69 shows a 15,000 volt, 800 ampere, FK-32-B
breaker with tank lifter and one of the tanks dropped to show the
type of contacts used.

The fixed contacts for the FK-32-A breakers of 400 and 600
amperes are of wedge construction, double break per pole and
make sliding contacts under heavy pressure when the breaker is
closed.

The fixed contacts for the 800 and 1200 ampere FK-32-A
breakers and all FK-32-B breakers are of laminated brush con-
struction and double break per pole. Wiping motion at closing
insures clean surfaces on the wedge or brush contacts. With all
sizes, the arc is broken on secondary renewable contacts of copper,
which close and open after the main contacts. The operating
mechanism is simple and positive in action, with the breaker
opening by gravity and compression springs. The frame supports
the breaker mechanism and the standard breaker units, each
with its own tank.

The tanks are approximately elliptical in cross-section, of
heavy sheet steel lined with treated pressboard to protect the

112 SWITCHING EQUIPMENT FOR POWER CONTROL

tank against the action of the arc. Strong supporting rods
hook at the bottom of the tank and, extending through the cover
above, hold the tank firmly.

FIG. 69. — General Electric Co. oil circuit breaker, type FK-32.

Ratings. — The rupturing capacities assigned to the FK-32-A
breakers are 1900 amperes, at 15,000 volts, 4370 at 7500, 7670 at
4500, 14,300 at 2500, while for the FK-32-B they are 2900 at
15,000, 6670 at 7500, 11700 at 4500, 21,800 at 2500 volts.

Type K-35.— The FK-35-Y and FK-35 breakers are also built
on the standard unit construction, and are intended for lower
voltages and lower currents than the FK-32- A and FK-32-B.
The rupturing capacities assigned to the FK-35 are 2100 at 7500,
3900 at 4500, 7550 at 2500 and 20,000 at 750 volts.

The types FK-32A and FK-32B oil circuit breakers can be
furnished for manual operation mounted on panel, panel frame,
or remote on framework and for solenoid operation mounted on
framework or in cell.

Cell Type. — For masonry compartment mounting, the FK-52B
breaker as shown in Fig. 70 is built for 15,000-volt service for
mounting on four-foot centers and for 25,000-volt service on six-
foot centers. Each unit is supported on steel bedplates in a sepa-

OIL CIRCUIT BREAKERS 113

rate cell compartment and is leveled and bolted to these plates.
The operating rod of each pole passes up through the top of the
cell and a hand or solenoid mechanism can be furnished for operat-
ing all of the poles at the same time.

FIG. 70. — General Electric Co. oil circuit breaker type K-52B.

The operating mechanism is designed to produce parallel
movement of blades. It has rustproof parts and noncorrosive
pins. The breaker opens by gravity assisted by springs on the
mechanism. An oil dash is used to buffer the mechanism at
the end of the opening stroke and balancing springs help to
carry the weight of the moving parts in closing. Provision is
made for the insertion of a removable lever for emergency
operation.

114 SWITCHING EQUIPMENT FOR POWER CONTROL

The tanks are approximately elliptical in cross-section and
are made from heavy sheet steel, acetylene welded, and lined
with pressboard. They are supported from the cover by bolts,
which hook under the bottom of the tank and pass through the
cover where they are securely fastened. Oil gauges and gas vents
are provided for all tanks.

The bushings for 15,000 volts are of one-piece wet-process
porcelain extending below the level of the oil. For 25,000 volts a
short extension is clamped to the main insulator, thus giving the
contacts a greater depth in the oil.

The main contacts are of laminated brush construction making
end contact with heavy and uniform pressure, without any ten-
dency to force any laminations of the brush apart. Wiping
motion at closing keeps the contacts clean.

Up to and including 1200-ampere capacity, round studs are
screwed and sweated into the brush block; 1600-and 2000-ampere
capacities have laminated studs.

Ratings. — The 25,000 volt FK-52-B have rupturing capacities
of 3450 amperes at 25,000, 6400 at 15,000 while the 15,000-volt
FK-52-B have rupturing capacities of 5800 at 15,000, 13,350
at 7500, 23,500 at 4500, 43,500 at 2500 volts.

Type H. — The ' H ' line of breakers covers the high rupturing
capacity types used principally in stations distributing at the
generator voltage and handling large amounts of power. These
breakers have one tank per lead, six for a 3-pole breaker,
the tanks being cylindrical and normally located in masonry
compartments. The H-l breaker was the original pneumatically
operated breaker, the H-2 was the electro-pneumatically oper-
ated, the H-3 was and still is the motor operated breaker with
pots 8 inches in diameter, the H-4 was the high voltage design
of 'H' construction using wooden pots, the H-5 was a hand
operated breaker. The H-6 was, and is the motor operated
with 10-inch diameter pots, and the H-9 is the motor operated
breaker with 12-inch diameter pots.

Old Type H3. — Fig. 71 shows one of the oil breakers supplied
to the generating stations and substations of the New York
Central & Hudson River R. R. With this type the leads
are brought to the bottom of the two metal tanks in each
compartment, and the circuit is completed through the
plunger rods that pass through insulated bushings in the
top of the tanks. These rods are connected together by

OIL CIRCUIT BREAKERS

115

metal crosspieces, and where the amount of current exceeds
that which the plunger rods can carry, laminated copper
brushes are used for bridging across between the pots. The
brushes and plungers are lifted by means of wooden rods, oper-
ated by a motor driven mechanism located at the top of the
breaker. Each pole of the breaker is installed in separate
masonry compartments, and fireproof doors are used for closing

FIG. 71. — General Electric Co. oil cir-
cuit breaker type H3.

FIG. 72.

in the compartments. This style of breaker is very compact and
is particularly well suited for connecting to busbars, located
directly below the breaker on a lower gallery.

For larger currents, where the plunger contacts cannot readily
take care of the amount of current to be handled, auxiliary con-
ducting bars are run outside of the pots from the bottom contact,
attached to insulator, to the top, where plates are placed on the
tanks and brushes span across between the two tanks of the
same phase.

Tank Section. — Fig. 72 shows a sectional view through a
tank of an H-3 breaker in the open position with the plunger rod

116 SWITCHING EQUIPMENT FOR POWER CONTROL

withdrawn to the extreme limit of the stroke. In the closed
position the tip of the plunger rod engages with the stationary
contacts at the extreme bottom of the tank and has a fairly long
bearing surface to secure self-cleaning action between the moving
rod and the stationary contacts. A baffle plate is provided
about half way through the oil and about 40 per cent, of the space

in the top of the tank is left
available as an air compression
chamber to take up the shock
of the explosion when opening
under load.

The cut represents what is
supposed to happen in the tank
at the instant of opening under
load. The arc has a tendency
to follow after the moving con-
tact and a gas bubble is formed
that is largely prevented from
following after the moving con-
tact by the action of the baffle
plate. This minimizes the dis-
turbance of the oil in the upper
part of the tank.

By the adoption of the de-
mountable type of tank con-
struction shown in Fig. 73 the
time needed for taking down a
tank is reduced to a minimum
and by keeping a few spare
poles available a new one can
be quickly substituted and the
replaced one examined when a
suitable opportunity arrived.

This same feature has been

embodied in the H-6 and H-9 types of breakers to gain the
same advantages.

Type H-6. — To secure greater rupturing capacities than could
be obtained in the 8-inch pots of the H-3 breakers, the H-6 line
of breakers was brought out with 10-inch diameter pots and these
in turn have been followed by the H-9 line of breakers with 12-

FIG. 73.

OIL CIRCUIT BREAKERS

117

inch pots. Still larger pots can be supplied if necessary, or two

or more pots used in series to obtain greater rupturing capacity.

Fig. 74 shows a type H-6 breaker, 1200 amperes, 15,000 volts,

with the parallel arrangement of tanks. This is the manner in

FIG. 74. — General Electric Co. oil circuit breaker type H6 with parallel pots.

which the breaker is normally arranged, but for certain conditions
such as for bus sectionalizing circuits, the tandem arrangement of
pots as show in Fig. 75 works out to advantage.

These breakers are usually made bottom connected but the
parallel pot breakers can easily be arranged with the rear tanks
top connected. With the tandem pots, all can be made top con-
nected if this best works into the scheme of wiring.

With the H-9 breakers in a recent installation the position of
the pots was a compromise between the parallel pot and the
tandem and might be described as the staggered pot arrange-

118 SWITCHING EQUIPMENT FOR POWER CONTROL

ment. The pots were all top connected and the front pots were
sufficiently to one side of the rear pots that the leads could be
run straight back without any interference. Other modifica-
tions of the *H' line of breakers can be made to meet local con-
ditions.

FIG. 75. — General Electric Co. oil circuit breaker type H6 with tandem pots.

Mechanisms. — The mechanisms for the types FH-3 and FH-6
oil circuit breakers have the following features:

Speed. — The contacts part in 0.2 seconds after contacts of over-
load relay or control switch close, and the switch is completely
opened in 0.59 seconds. A complete cycle, opening and closing
can be accomplished in 2 seconds. Torsion springs counter-
balance the weight of the mechanism, making equally rapid
motion for either stroke.

Compression springs throw the breaker about 1 inch into con-
tact on closing and about 1^ inches from full stroke on opening,
both with a rapid movement. The stroke is completed by the

OIL CIRCUIT BREAKERS 119

motor. The motor completes the stroke begun by the compres-
sion springs and compresses the operating springs at the end of
each stroke (either opening or closing), thereby preparing the
breaker for the reverse operation.

The master finger closes a circuit paralleling the safety switch
at the first movement of the switch mechanism, thereby insuring
the completion of the operation.

The magnetic clutch disconnects the motor from the mechan-
ism when not needed, preventing injury to the motor by sudden
stopping of the mechanism.

Ratings. — The rupturing capacity assigned to these breakers
is as follows:

Volts 2,500 4,500 7,500 15,000

H-3 Amperes 75,000 40,300 23,000 10,000

H-6 Amperes 135,000 72,600 41,400 18,000

H-9 Amperes..... 150,000 92,700 52,900 23,000

For the smaller current ratings at the lower voltages the ratings
are limited to 100 times the normal ratings of the breakers as the
carrying capacities of the contacts are the limiting features.

High Voltage Breakers. — All of the high voltage breakers of
the General Electric Company now in standard production are of
the 'K' lines with various sub-number designations, the numerals
such as 24, 26, 36, etc., being followed by the letter 'O ' where the
breakers are used for outdoor service. These breakers are built
for pipe frame mounting up to 50,000 volts, for structural frame
mounting for 73,000 volts and for platform mounting for higher
voltages.

Type FK-24.— Fig. 76 shows a 15,000-volt 500-ampere FK-24
breaker for indoor service. Each pole is in a separate steel tank,
the individual tanks being on a common frame and operated by
a common mechanism that is designed to produce parallel move-
ment of the blades. This mechanism has rust proof parts and
noncorrosive pins. Provision is made in the mechanism for
insertion of a removable hand-closing lever. Where space is
' limited, the breaker can be furnished with a one-piece top, sup-
porting all of the elements.

Hung 'from the top are the tanks of heavy sheet steel, acetylene
welded, with separate tank for each pole, and oil gauges for
each tank. The bushings are one-piece porcelain made by the
wet process and extending below the level of the oil. These

120 SWITCHING EQUIPMENT FOR POWER CONTROL

bushings are held in clamps with interchangeable metal plates
with trued surfaces to get proper alignment and to facilitate re-
moval-and inspection.

The fixed contacts are made of forged copper fingers at the end
of the terminal studs that pass through the bushings. The
fingers are flared at the tips and one set is extended to act as

FIG. 76. — General Electric Co. oil circuit breaker type FK24.

arcing tips. The movable contact blade is screwed and clamped
to the operating rod. The contacts are wedge-shaped which
confines the arc to their top edge and to the flared portion of the
finger tips.

Ratings.— The rupturing capacities of the 35,000-volt FK-24
breaker is 1100 amperes at 35,000 volts; 1670 at 25,000; for the
25,000-volt breaker 1500 at 25,000; 2800 at 15,000 and for the
15,000-volt breaker 2500 at 15,000, 5750 at 7500.

Type FK-26.— Fig. 77 shows a frame mounted FK-26 breaker
for indoor service at 45,000 volts. Most of its features corre-
spond with those of the FK-24 previously described, but the

OIL CIRCUIT BREAKERS

121

general dimensions are considerably larger and the bushings
instead of being of the porcelain type are of built up material
with a contact tube extending through it and binding together
the upper and lower sections. A maple cover keeps out dirt and
protects the end of the bushing. Porcelain ends prevent injury
to the bushing by any arc or discharge that might occur.

FIG. 77. — General Electric Co. oil circuit breaker type K26.

The interior of the 45,000-volt bushing has the contact tube
surrounded by an insulating material and the bushing filled with
an insulating compound of high dielectric strength. The bush-
ing for 70,000-volt service has a set of cylinders of insulating
material concentric with the contact tube, the whole being filled
with an insulating compound. At the bottom of the 70,000-

122 SWITCHING EQUIPMENT FOR POWER CONTROL

volt bushing that is under the oil a static shield is provided that
partly surrounds the contacts.

Type FKO-26.— Fig. 78 shows the FKO-26 breaker for frame
mounting outdoor service, this differing principally from the
indoor type in the waterproof covering for the operating mechan-
ism and the porcelain rain shields over the portions of the bush-
ings that are exposed to the weather. With all of these breakers,

FIG. 78. — General Electric Co. oil circuit breaker type K026.

the cast-iron support built into the bushing serves as the means of
attaching it to the breaker. Where bushing transformers are
used, this cast-iron housing is made large enough to house and
protect them.

These breakers can be supplied for floor mounting or for frame
mounting. The framework for the 50,000-volt breaker is made
of pipe while that for the 73,000 is made principally of channel
irons.

The rupturing capacities for the 70,000-volt breakers are 1950
amperes at 70,000 volts; 2200 at 50,000; 2500 at 45,000; 3130 at

OIL CIRCUIT BREAKERS

123

37,000 and for the 45,000, 1600 at 45,000; 2050 at 37,000 and 3260
at 25,000.

Type FKO-36.— Fig. 79 shows a floor mounting FKO-36
for outdoor service, this breaker having a guaranteed rupturing

-.1

FIG. 79. — General Electric Co. oil circuit breaker type K036.

capacity of 3290 amperes at 110,000 volts. The sides of this
tank are practically flat but the arc is broken under the oil in a
special explosion chamber shown in Fig. 80.

Fia. 80. — General Electric Co. oil circuit breaker type K036. Explosion
chamber.

The function of this explosion chamber is based on the theory
that by confining the arc to a largely restricted space a high
pressure will be developed tending to blow the arc away from
the contact causing its rapid extinction. The steel cylinder
forming the explosion chamber can be readily made of ample
strength for the pressure developed.

124 SWITCHING EQUIPMENT FOR POWER CONTROL

Ratings. — The FK-36 ' and FKO-36 are built with various
sized tanks and given varying rupturing capacity ratings. For
example at 155 K.V. breakers are available with rupturing capa-
city ratings of 900, 2300 and 3500 amperes; for 135 K.V. the
ratings are from 950 to 3600 amperes; for 115 K.V. from 1000
to 4400 amperes, etc.

Modifications of these breakers are available and in services
up to 160,000 volts and designs have been made for service at
220,000 volts and such breakers are now being built for
California.

WESTINGHOUSE OIL CIRCUIT BREAKERS

While the Westinghouse Company had made oil switches and
oil circuit breakers in various forms prior to 1904, their annual
catalogue of that year was their first one with various lines of oil
circuit breakers and switches listed and described in it. At that
time the term oil switch was applied to those pieces of apparatus
in which the contacts were of the knife type that did not have
any tendency to come open and the term oil circuit breaker was
applied to those pieces of apparatus so designed that the con-
tacts tend to separate and were only held in the closed position
by means of triggers and toggles.

In the descriptions that follow, the oil circuit breakers are
taken up about in the order of their rupturing capacity in place
of alphabetically by type letters.

Knife Contacts. — Type I oil circuit breakers, manually oper-
ated, non-automatic, for indoor service, single and double
throw, are made for capacities up to 60 amperes 4500, volts A.C.,
interrupting capacity at rated voltage, 300 amperes. The
characteristic features of the type I oil circuit breakers are: knife
blade contacts submerged in oil; live parts carried on porce-
lain base affording high quality of permanent insulation between
adjacent poles, and between frame and live parts; small space
required for mounting; light weight; tanks removable without
disturbing contacts, making easy accessibility of parts for purpose
of inspection and repairs; enclosure of all live parts; and low first
cost. The breaker is essentially a knife switch submerged in oil
and arranged for external operation.

Type D. — Type D oil circuit breakers are manually operated
non-automatic made for indoor, outdoor and subway service,
single and double throw, for capacities up to 300 amperes, 1500

OIL CIRCUIT BREAKERS 125

volts, 200 amperes, 4500 volts, alternating current, interrupting
capacities at rated voltage 700 to 800 amperes.

These non-automatic oil circuit breakers have a wide range of
application, being made for indoor service in panel mount-
ing, direct wall-mounting, remote-control wall or pipe mount-
ing, and for subway mounting.

Outdoor Type. — The outdoor form of wall or pole mounting
breaker is primarily intended for service in exposed places.

The wall or pole mounting breaker is enclosed in a weather-
proof case having lugs cast thereon for mounting the breaker on
a wall or pole. On these outdoor breakers a crank handle is used
for operation. The leads are brought out underneath the top
part of the case, through sealed bushings at the side and under-
neath the main casting. The sealing-in of the bushings prevents
the entrance of rain or moisture to the interior of the breaker.

Subway. — The subway form of breaker is intended for mount-
ing in subways, manholes, or other places where a breaker may
be required to operate submerged. This subway form of breaker
is made in 2, 3 or 4-pole, single and double throw, for capacities
up to 200 amperes, 4500 volts.

The housing for the subway breaker complete, including the
oil tank, is of cast iron. All housing joints are made water-
proof by the use of gaskets. The housing has lugs cast thereon
for mounting the breaker on the wall of the subway, manhole
or other place of mounting.

The leads enter the breaker housing through individual water-
proof bushings in the top of the case. The operating handle is
provided with a waterproof stuffing box and is latched in either
the "on" or "off" position.

Features. — The characteristic features of the type D oil
circuit breakers are: knife blade contacts submerged in oil and
protected by auxiliary arcing contacts; live parts carried on in-
sulating supports affording a high quality of permanent insulation
between adjacent poles, and between the frame and live parts;
all parts supported by a single frame easily mounted on panel,
wall, pipe frame, post, bracket, or other vertical support; small
space required for mounting; accessibility of parts for the pur-
pose of inspection and repair; enclosure of all live metal parts;
simple but rugged construction.

Tanks. — The oil tanks are rectangular in shape and are made
of heavy sheet iron. Individual insulating cells on single-throw

126 SWITCHING EQUIPMENT FOR POWER CONTROL

breakers, and an insulating lining on double-throw breakers, are
used as an additional protection against arcing from current-
carrying parts to the metal of the tank. Where the individual
insulating cells are used on the single-throw breakers, they form
a separate compartment for each pole. While the tank is
securely fastened to the breaker frame, the construction permits
of easy removal for the purpose of inspection and repair.

The tanks are deep to allow ample space above the oil level
to act as an expansion chamber for the arc gases, and to reduce
slopping of the oil from internal disturbances. The gases are
vented through the clearance between the wooden operating
rod and the frame.

Type F. — Type F oil circuit breakers are made manually
and electrically operated, non-automatic and automatic, for
indoor and outdoor service, single and double throw, for capaci-
ties up to 3000 amperes, 13,200 volts A.C., interrupting capaci-
ties at rated voltage, 1000 to 15,000 amperes.

These type F oil circuit breakers comprise a complete line
of moderate-capacity, non-automatic and automatic, manually
and electrically operated breakers. For indoor service, the
breakers are made in the panel mounting, and remote-control wall
or pipe mounting forms, and for outdoor service in pole or sub-
way mounting forms.

Among the features of the type F breakers are: Wedge and
finger-type contacts. Auxiliary arcing contacts. Submersion
and opening of all contacts under oil. Quick opening of contacts,
assisted by arcing tip springs. Open position maintained by
gravity. Inability to hold full automatic breaker in the closed
position when an excessive overload or short circuit exists on the
line. Strong tanks and tank supports. Tanks removable with-
out disturbing the operating mechanism or contacts, making in-
spection easy. Ample air space at the top of the tank to allow
for gas expansion. Insulating lining in the tanks. Isolation of
poles by individual cells. Self contained rnultipole hand- or elec-
tric-operating mechanism on the multipole single-tank breakers.

The type F oil circuit breakers are made non-automatic
and full-automatic, direct or remote-control manually operated;
and non-automatic and automatic electrically operated.

Type F-l. — Fig. 81, shows a type F-l indoor manually
operated remote-control pipe mounting three-pole single-throw
200-ampere, 4500-volt breaker with micarta tubes over terminals

OIL CIRCUIT BREAKERS 127

and with tank removed. The standard overload-trip .range of
these breakers is 80 to 160 per cent, of the normal full-load cur-
rent rating or primary rating of the current transformer in the
trip coil circuit.

FIG. 81. — Westinghouse oil circuit breaker, type F-l.

Transformer Trip. — For this method, type F automatic
breakers are made with trip coils mounted on the coverplate of
hand operated breakers or on the electric mechanism of electri-
cally operated breakers. A single 5-ampere coil is regularly
used on single pole and 2-pole breakers, and two 5-ampere
coils on 3-pole and 4-pole breakers. For use on 2-phase or
3-phase, where accurate overload tripping is not required on
a single-phase overload or short circuit, single coil 3- and
4-pole breakers having only one special 8.7-ampere overload
trip coil, are obtainable. This special trip coil can be con-
nected to two current transformers in "vector parallel," in
which case the single-phase overload accuracy is within good
operating limits of the polyphase calibration.

Series Trip. — For series tripping, type F indoor breakers
are made with alternating-current series-overload trip coils
mounted in the switchboard cover plate dry insulated, for
voltages up to 2500 and capacities from 10 to 300 amperes.

Multiple -Multipole. — Multipole breakers having a single
mechanism and tank are made up to maximum capacities of 800

128 SWITCHING EQUIPMENT FOR POWER CONTROL

amperes. In addition, type F-3 breakers, either manually or
electrically operated remote control, can be supplied in capacities
up to 3000 amperes by using 3 or 4-pole standard units with
the contacts connected in multiple for each pole, (multiple-multi-
pole). Type F-3 breaker frames are specially designed for this
purpose.

Manual Operation. — Manually operated direct control break-
ers are made either for panel or panel-frame mounting, or for
remote control wall or pipe mounting. The type F-2 multiple
single-pole wall mounting breakers (a multipole breaker made
up of single pole units) and the type F-3 multiple-multipole wall
mounting breakers (a multipole breaker made up of standard
remote control 3 or 4-pole units to form one high capacity
multipole breaker) when equipped with appropriate fittings, can
be used for cell mounting, erected in brick, asbestos lumber, or
concrete structure, with each pole enclosed in a separate com-
partment.

Electrical Operation. — Electrically operated multipole single-
tank breakers are made with self-contained mechanisms for
either wall or pipe mounting. The multiple single-pole electric-
ally operated breakers are made for either wall or pipe mounting
with separate operating mechanisms placed above, below, or
behind the breaker, while the electric operating mechanism of the
multiple-multipole breakers can be mounted only below the
breaker.

Tanks. — Multipole single tank construction is used on all
type 'F1 breakers, except the type F-2 multiple single-pole, and
the type F-3 multiple-multipole, which use one tank per pole.
The oil tanks are rectangular in shape and are made of heavy
sheet-iron with all seams lap-welded, the bottom being flanged
and welded on the outside of the tank sides. As an additional
protection from arcing, individual insulating cells form separate
compartments for each pole where one tank is used on multipole
breakers.

Studs. — The terminal studs or bushings with stationary
contacts or feet on the lower extremity are supported by one-
piece vertical pillar type porcelain bushings clamped to the
framework. The studs and micarta-tube details are clamped to
these insulators. This construction avoids the use of babbitt
and cement, thus reducing the time and labor of maintenance.

OIL CIRCUIT BREAKERS 129

Contacts. — The main moving contacts are wedge type. The
main stationary contacts consist of fingers of the "controller"
type arranged in pairs facing each other so as to make perfect
contact on the two surfaces of the moving contact wedge when
the breaker is closed. The contact tips on the end of the fingers
are supported on the ends of thin flat steel springs, permitting the
contact to move in all directions and to automatically align itself
on the wedge, thus insuring that the full carrying capacity of the
contacts is always available. This spring is shunted by a liberal
copper-leaf shunt to conduct the current from the tips to the
terminal stud.

Arcing Contacts. — These are made of the butt type to protect
the main contacts from the action of arcs at breaking. The
stationary member consists of a spring plunger and copper
arcing tip mounted on the support of the main contact. A flex-
ible copper wire shunt carries the current from the stud to this
tip. A copper bolt is carried on the conducting cross-bar of the
moving contact element and serves as the moving arcing contact.
The auxiliary arcing contacts maintain contact for a considerable
distance after the main contact fingers have broken contact.
This time interval is predetermined by the amount of separation
of the main contact fingers produced by the steel stop and serves
to fully protect the main contacts.

Type H. — These oil circuit breakers are small capacity manu-
ally operated single-throw breakers for indoor use (dust-proof
wall mounting) and outdoor use (weatherproof, wall or pole
mounting). These breakers supply the need for a simple,
reliable, inexpensive oil circuit breaker for use in general indus-
trial applications. They are particularly useful for controlling
motor circuits, or other loads of low power factor, where exces-
sive arcing would occur when using an air-break switch at low
power factor, thus making the use of an oil circuit breaker
advisable. The cylindrical-rod butt-type contact is used. The
contacts consist of cylindrical rods, the lower one backed by
spiral springs to insure contact. This type of contact is used
on the multiple unit control system of heavy street-railway
equipment and has been adapted with great success to oil cir-
cuit breaker practices. It insures good contact at all times, and
prevents any possible failure due to the eating away of the con-
tact by continued arcing. The compression springs take up any

130 SWITCHING EQUIPMENT FOR POWER CONTROL

wear that may occur. The contacts have long life, and are
readily removed and replaced when necessary.

Type QF. — The type 'QF' motor starting oil circuit breakers
shown in Fig. 82, are especially designed for starting, in connec-
tion with auto transformers, 3 phase squirrel-cage induction
and self-starting synchronous motors up to 720 H.P. When
properly applied they protect the motor in the running position
from heavy overloads and short circuits, and guard it against
the sudden application of full voltage to the motor after it has
slowed down or come to rest following an interruption of power.

FIG. 82. — Westinghouse type "QF" Motor starting oil circuit breaker.

The type QF motor starting oil circuit breaker is a double-
throw breaker with special moving and stationary contact
arrangement. In effect, it is a 3-pole, double-throw breaker
with three additional terminals used to complete the auto-
transformer circuits when the breaker is in a starting position.
The auto transformers are mounted separately from the breakers.
The tap leads of the transformers are permanently connected
to the motor leads.

Type B. — The modern type 'B' oil circuit breakers comprise a
line of medium capacity breakers built of three different forms,
namely, types 'BA,' 'B-2/ and 'B-13/ each with a different
interrupting capacity, different maximum voltage and details of
construction.

These breakers have a wiping and self-cleaning form of lami-

OIL CIRCUIT BREAKERS

131

nated brush contact, protected by butt arcing contacts. The
opening of all contacts occurs under oil with a positive direct
gravity break assisted by spring acceleration, and with open
position maintained by gravity. The type 'B' circuit breaker
is in general a common-frame circuit breaker. The type 'B-A'
has a tank per pole in all sizes. The type 'B-2' has a tank per
pole in the 300-ampere and 600-ampere sizes, but a single tank
construction in the other sizes. The type 'B-13' has a tank
per pole in all sizes.

FIG. 83.— Westinghouse type "BA" oil circuit breaker, 300 amps., 15 K.V.

Manually operated circuit breakers are actuated by a handle
mounted in the switchboard cover plate. When the breakers are
supplied with automatic overload trip with remote control, an
accelerating spring device is used to quicken the opening of the
contacts, and this device, assisted by the arcing contact springs,
gives to the moving parts an acceleration greater than that caused
by gravity.

Fig. 83 shows a 4-pole 300-ampere, 15,000 volt 'BA'
oil circuit breaker with one tank removed, showing contact
details on one pole. Fig. 84 shows a 3-pole-solenoid operated

132 SWITCHING EQUIPMENT FOR POWER CONTROL

'B-13' breaker 600 amperes 25,000 volts arranged for pipe frame
mounting. All of the following sizes of circuit breakers can be
supplied either manually or electrically operated and either auto-
matic with transformer trip coils or non-automatic. The manu-

FIG. 84. — Westinghouse oil circuit breaker type B13.

ally operated breakers can be panel or panel frame mounting or
remote control, while the remote- control breakers, both hand and
electrically operated, can be furnished for wall mounting or pipe
frame mounting. All can be furnished in 2, 3 or 4-pole types.

Maximum

Amperes

Interrupting
capacity

T\/f

Type

ivi a xim u ni
volts

in arc
amperes

60 cycle

25 cycle

at rated

voltage

300

400

15,000

1,350

600

750

7,500

3,500

B-2

300

400

15,000

1,900

B-2

300

400

25,000

960

B-2

600

750

15,000

1,900

B-2

600

750

25,000

960

B-2

1,200

1,350

15,000

1,900

B-2

1,500

1,750

7,500

3,000

B-2

1,750

2,000

7,500

3,000

B-2

2,000

2,250

7,500

3,000

B-13

300

400

25,000

l',630

B-13

600

750

25,000

1,630

B-13.

1,200

1,350

15,000

3,400

OIL CIRCUIT BREAKERS 133

Multiple-Multipole. — These type B oil circuit breakers can be
furnished for applications requiring a breaker having current
carrying capacities up to 6000 amperes, 60 cycles. As indicated
by their name, these breakers consist of a number of multipole
single frame breaker units, each unit having its poles connected
in multiple to serve as one phase leg. All phase leg units are
operated simultaneously by means of a common operating
shaft and bell cranks. For example, a 4800-ampere 3-pole type
B-2 multiple-multipole breaker consists of three 2000-ampere, 3-
pole units. The poles of each 3-pole unit are connected in
parallel, thereby forming one 4800-ampere pole. Three such
poles units operated simultaneously meet all the requirements of
a 4800-ampere 8- pole breaker.

Connections. — In making connections to a multiple -multipole
breaker care must be exercised not to "bus" the connections at
the breaker studs on both sides. If this is done the contact
resistance of the connections is the only source of voltage drop.
Thus a slight increase in contact resistance on one stud of a
"bussed" connection results in the other studs in the same paral-
lel circuit taking more than their share of the current, heating
develops and then the results are cumulative. Any difficulties
from such a source can be overcome by using cables to connect
to the breaker on at least one side. The number of cables should
be the same as the number of parallel circuits through the breaker
or multiples thereof. The resistance of the relatively long cable
connections is such that even a 100 per cent, change in the contact
resistance at one stud would be but a small percentage change in
the total resistance of the total parallel circuit and no uneven
distribution of the current results.

Mounting. — The type B breakers are arranged for either
panel, panel frame or pipe frame mounting direct-control; and in
the remote-control form, for wall or pipe frame mounting. The
remote-control breakers can be mounted in cells, the single frame
circuit breakers being mounted as a unit in one cell, which can be
made of brick, asbestos lumber, or concrete.

Tanks. — These are rectangular in shape except on the 1200
ampere and 2000-ampere type B-13 breakers which have elliptical
tanks similar to those supplied on the type E line of breakers.
The tanks are made of heavy sheet-iron, with all seams lap-
welded, the bottom being flanged and welded on the outside of
the tank sides. The tanks have a micarta lining, and where one

134 SWITCHING EQUIPMENT FOR POWER CONTROL

tank is used on multipole circuit breakers, individual insulating
cells form separate compartments per pole.

The tanks are especially deep to give a large head of oil over
the contacts, to allow ample space above the oil level to act
as an expansion chamber for the arc gases, and to reduce spilling
of the oil from the internal disturbances. On the type B-A and B-2
circuit breakers, the gases are vented around the lifting rod.
The type B-13 circuit breakers are equipped with specially
designed baffled vents.

Moving Contacts. — The main moving contacts are of the
laminated butt brush type. When the high contact pressure
used is imposed on the movable contact (the butt brush), its
contact surface spreads out on the stationary contact (a plane
surface) producing a wiping action which automatically cleans
both the stationary and moving contact faces.

Stationary Contacts. — The stationary contacts are mounted on
the lower end of the terminal studs and provide a liberal contact
surface. The moving contacts of each pole of the breaker are
connected to the mechanism by an insulating rod. The contact
pressure is obtained by adjustable features which equalize the
pressure on both ends of the moving contact element.

Arcing Tips. — The main contacts are protected from burning
when opening heavy overloads or short circuits by the use of butt-
type arcing tips. The moving member consists of a plunger
actuated by a spring mounted on the support of the moving main
contact brush. A copper arcing tip is bolted on the main sta-
tionary contact in such a position that the head makes contact
with a similar tip on the arcing plunger. These arcing tips are
easily and inexpensively renewed when burned. A flexible
copper strap shunt carries the current between movable plungers.

The arcing contacts maintain contact for a considerable dis-
tance after the main contacts open; and, being placed outside the
main contacts, the arc formed between them is automatically
blown away from the main contacts, the auxiliary contacts thus
taking all the arc.

Type E. — These oil circuit breakers were originally built for
hand operation only and designed for mounting in a masonry
compartment. In 1904 they were listed up to 100 amperes at
25,000 volts, 300 amperes at 16,500 volts, 600 amperes at 7500
and 1200 amperes at 3500. Their rating converted to the modern

OIL CIRCUIT BREAKERS

135

methods of figuring would be expressed in amperes corresponding
to about 65,000 K.V.A. at the various voltages mentioned.

Old Forms. — The smaller frame breakers that had been uti-
lized in the 300 and 600- ampere sizes for cell mounting became the
E-l breakers for cell mounting; the larger breakers for cell
mounting became the E-2 and the corresponding frame mounted
breakers became the E-3 and E-4, these being suitable for mount-
ing against a flat wall or on structural iron framing.

To facilitate erection, dismantling and repairs or inspection,
the design of the E-2 was modified so that each pole could easily
be slid into a steel channel set in the
barrier walls between poles. The result-
ing design with a soapstone top was
known as the E-5 and the pole width
could be modified within certain limits
by changing the size of the soapstone
base.

Later Types. — When a definite width
became standard and the top was made
of steel in place of soapstone, the E-6
came into being and the same switch
for frame mounting became the E-7.

Where a breaker of the 'E' line was
desired but a smaller rupturing capacity
than that of the E-6 would suffice, a
smaller breaker was developed for cell
mounting known as the E-8, and for
frame mounting known as the E-9.
For the neutral circuits of generators
and for single phase circuits fed from
3-phase 4-wire systems, single-pole
solenoid breakers were developed, known
as the E-10, an adaptation of the older "E" mechanism being
used. Three-pole breaker design has the three poles on a com-
mon frame, although occasionally three independent solenoids
are used.

Fig. 85 shows a type E-6 cell mounting, electrically op-
erated breaker in the open position with one tank lowered and
two double doors of the cell structure removed.

Fig. 86 shows a 2000-ampere 4500-volt E-8 breaker, single-

FIG. 85. — Westinghouse
type ' ' E - 6 ' ' oil circuit
breaker, 300 amps., 25 K.V.

136 SWITCHING EQUIPMENT FOR POWER CONTROL

pole unit with tank removed, showing the stationary and mov-
ing contacts

The type E oil circuit breakers are particularly adapted to the
control of alternating-current circuits of capacity from 25,000 to
40,000 connected turbo-gen-
erator K.V.A. and voltages
not over 25,000. They are
designed for indoor mounting
apart from the switchboard
and for either manual or
electrical control.

Features. — The following
features particularly adapt
the type E breakers to their
class of service. Self-clean-
ing form of high-pressure
laminated brush; main con-
tacts protected by extra
heavy arcing contacts; sub-
mersion and opening of all
contacts under oil; quick
opening of contacts, assisted
by heavy accelerating spring;
open position maintained by
gravity; strong elliptical lap-
welded steel tanks and steel
tank supports; tanks remov-
able without disturbing the
operating mechanisms or con-
tacts, making inspection easy;
individual tanks enclose the
contacts of each pole of the
breaker; ample air space at
top of tank to allow for
proper gas expansion; in-
sulating linings in tanks; unit-type electrical operating mechanism
having closing, tripping, accelerating, and shock-absorbing fea-
tures self contained; manually operated breakers tripped free of
the mechanical remote control in the automatic overload-trip
forms; inability to hold full-automatic overload-trip forms of
breaker in the closed position when an excessive overload or

FIQ. 86. — Westinghouse type E8 oil
circuit breaker.

OIL CIRCUIT BREAKERS

137

short circuit exists on the line; each pole a complete unit,
operated by independently adjustable connecting rods to the
common electric or manual operating mechanism, and, in the
cell mounting forms, installed in a separate masonry compartment.
Ratings. — The following sizes are built in either two, three, or
four- pole breakers, manually or electrically operated.

Interrupting

Maximum Amperes

capacity

Type

Maximum
volts

in arc
amperes

60 cycle

25 cycle

at rated

voltage

E-6and E-7..

300

400

25,000

5,350

E-6and E-7..

600

750

25,000

5,350

E-6and E-7..

1,200

1,350

25,000

5,350

E-6and E-7..

1,600

1,800

15,000

10,000

E-6and E-7..

2,000

2,250

15,000

10,000

E-8and E-9..

600

400

25,000

2,200

E-8and E-9..

600

750

25,000

2,200

E-8and E-9..

1,200

1,350

15,000

4,500

E-8 and E-9. .

1,600

1,800

7,500

10,300

E-8 and E-9. .

2,000

2,250

4,500

18,200

Solenoid Control. — These breakers are operated by a solenoid
mechanism that is mounted above the poles on the cell mount-
ing breakers or on the floor for the wall, pipe frame or struc-
tural frame mounting breakers. The breaker is closed by a
solenoid and is held closed by a hardened steel latch and a trigger
which engage automatically. The closing solenoid is regularly
furnished for use on 125- volt (normal) direct- current circuits and
has a standard operating range from 70 to 140 volts. Coils for
other than standard voltage with the same proportionate range
can be furnished. Due to the wide operating range, breakers
with the standard coil can be satisfactorily operated from 110-
volt direct- current circuits.

Type E-6 and E-7 breakers have a device known as a "cut-
off" switch supplied as an integral part of the electric operating
mechanism. When properly connected and adjusted, it does
not allow an automatic breaker being held closed on over load
thus securing the trip-free feature.

138 SWITCHING EQUIPMENT FOR POWER CONTROL

Mounting. — These breakers are made for either cell or pipe
mounting. The cell mounting breakers, types E-6 and E-8, are
arranged for supporting the individual poles of the breaker in
fire proof compartments of brick, asbestos lumber, or concrete
structure with removable doors. The channel frame upon which
the manually operated mechanism or electrically operated mech-
anism is mounted is placed on top of the cell structure. This
construction provides, where necessary, for special wide spacing of
the poles when reactance coils, two sets of disconnecting switches,
etc., are used in connection with the breaker.

The pipe mounting breakers, types E-7 and E-9, are designed for
mounting on horizontal pipe supports. All capacities of both
types have the same dimensions of horizontally arranged pipe
centers so that the installation of several different capacities
can be made on a common pipe frame structure.

Unit Construction. — The type E breakers are made up of
single-pole units, each having its own steel supporting frame and
toggle arrangement for operating its moving contacts, so that all
contact adjustments are made and locked before shipment.
In the multipole breakers these individual pole mechanisms are
in turn connected to a common operating mechanism controlled
by the manually operated handle and trip coils or by the electric
operating mechanism.

The individual toggle arrangement for each pole permits each
complete pole to be placed in position and properly lined up.
This arrangement also permits the adjustment of contact pres-
sure and contact travel of each pole to be made independent of
the other complete breaker poles.

On the cell mounting breakers the operating mechanism
is mounted on a plate and channel frame structure fastened to the
top of the cell structure. On the pipe mounting breakers the
mechanism is mounted on the floor, to one side of the poles.

Latest Improvements. — Some of the latest improvements in
the E-6 breakers are the tank cradle and tie rod method of sup-
porting the tanks to obviate the possibility of the tanks being
blown off by an explosion and the furnishing of reversed brushes
on all breakers where the short-circuit current on the system
might rise to such a point that the magnetic stresses would
straighten out any ordinary brush of the usual wound copper
strip construction. Instead of the brush in the form of a half
ellipse being on the movable member, that member was made

OIL CIRCUIT BREAKERS

139

essentially straight and brushes in the form of a quarter of an
ellipse were placed on the stationary contacts with the concave
side down and turned in so that the magnetic force increased the
pressure between the stationary and movable members instead
of tending to diminish the pressure by straightening out the
brush when it was mounted with the concave side downward.
The new moving element is so stiff mechanically that the mag-
netic forces cannot distort its shape.

Type C. — The modern type C oil circuit-breakers are adapted
to the control of circuits of large capacity, up to 60,000, con-
nected turbo-generator K.V.A. and up to 15,000 volts. They are
made for indoor cell mounting and for electrical operation only.
They are especially used for lining up with existing installations
of similar breakers, and are noted for their great compactness
with high rupturing capacity.

The distinctive features of the type C breakers are the self-
contained multipole operating mechanism with positive and
direct solenoid operation, quick opening hastened by accel-
erating springs and open position maintained by gravity. The
contacts open under oil, and are of a highly efficient form of
brush with butt arcing tips. There is an expansion chamber
with baffled vent for the arc gases. The poles are isolated
in separate tanks and cells, the elliptical tanks being very strong,
with exceptionally strong fastenings, and removable without
disturbing any other part of the breaker.

Ratings. — The following sizes are built in three or four-pole
units electrically operated with either vertical or horizontal
arrangement of leads.

Maximum

Amperes

Interrupting
capacity

Type

60 cycle

25 cycle

volts

amperes
at rated
voltage

CG
CG

600
1 200

750
1 350

15,000
15,000

14,000
14,000

C-2
C-2
C-2

600
1,200
2,000

750
1,350
2,250

25,000
25,000
15,000

8,000
8,000
15,000

C-2

3,000

3,400

2,500

86,300

140 SWITCHING EQUIPMENT FOR POWER CONTROL

The breaker is designed for supporting the individual poles in
fireproof compartments of brick or concrete structure with
removable doors. Each pole of the breaker is covered by a cell
door consisting of a metal frame with asbestos panels and hinged
at the top to the iron mechanism base. The electric operating
mechanism which controls all poles simultaneously is mounted on
the cast-iron bedplate or base which covers the top of the cell
structure.

FIG. 87. — Westinghouse type "C" circuit breaker installation.

Cells. — These breakers worked into very satisfactory structural
arrangements, particularly in plants where the galleries could be
so arranged that one row of breakers would be on a gallery below
the busbars and the other one on a gallery above the bus. They
also were well fitted for installations with the bus bar back of the
breakers and particularly for a feeder and group arrangement,
such as has been employed in many plants, that permit a generator
to be readily used with either of two feeder groups immediately
adjacent to it or to be connected to a main bus to facilitate paral-
lel operations or tied on to a transfer bus to allow it to feed
any set of feeder groups. Fig. 87 shows an installation of 'C'

OIL CIRCUIT BREAKERS 141

breakers arranged for group feeder operation with one row of
breakers on an upper gallery with the generator bus back and
above it, and a main bus back of the lower part of the breaker.
On the floor below, the feeder breakers are arranged with the
bus above them. There are two complete sets back to back
arranged for a ring system.

Tanks. — In the type CG breaker, the tank construction is the
same as that for the type G-l oil circuit breaker, consisting of
heavy sheet steel tanks, double lap-welded on the vertical
seam, and having the bottom flanged outside and lap-welded.

In the type C-2 breaker, the tank construction is the same as
that for the type "E" oil circuit breaker except that the top
engages a flange on the expansion chamber instead of on the
supporting frame as in the "E" breaker.

In the type CG breaker, the expansion chamber is supported
from the 3^-inch sheet steel bedplate by strong steel rods.

In the type C-2 breaker, wood strain insulators support the
expansion chamber from the slate base portion of the bedplate,
thus completely insulating the tank unit from ground.

In both types of breakers, the expansion chamber provides a
large space above the oil level, into which the gases formed
between contacts by the arc, at the time of opening the circuit,
can expand. Each chamber has a vent to provide an exit for
gases and these vents are baffled to prevent the throwing of oil
when the breaker opens under heavy overloads or short circuits.

Mechanism. — The mechanism with operating coils is self
contained on a single bedplate or base. To make the opening of
the breaker rapid and positive, accelerating springs are used to
force the breaker to the open position. Dashpots absorb the
momentum of the mechanism in closing and in opening. The
bedplate is also fitted with leather bumpers to support the weight
of the moving contacts and rods after the dashpots have brought
the breaker to rest in the open position.

Type O. — The modifications necessary for a 60-cycle breaker
of about 4000-amperes capacity, involved the use of two
sets of studs in parallel or a total of four studs per pole and this
logically lead to a circular design of tank as special round tank E
breakers and these worked out so well that a modified type of
mechanism was developed and a line of breakers with 16-inch
diameter round tanks became the type O-l, while corresponding
breakers with 20-inch tanks became the type O-2.

142 SWITCHING EQUIPMENT FOR POWER CONTROL

With the type O-l or O-2 breaker, as well as with the
E-6, the unit type of construction is used and the pole units
can be assembled as 2, 3 or 4-pole units with a single mechanism
for operating all the poles simultaneously. Each pole is nor-
mally arranged to slide into a channel iron recess in the barriers
between adjacent poles and the two channels set back to back

FIG. 88. — Westinghouse type "O-l" oil circuit breaker.

occupy the same thickness as a 4-inch barrier wall. This results
in the minimum spacing between poles for normal construction.
The substitution of an "I" beam for a double channel results in
the saving of a centre distance of an inch, while the locating of the
channels outside of the barrier walls means slightly greater
spacing.

A typical 3-pole breaker type O-l is shown in Fig. 88, this
being the type of the breakers at the West Farms substation
of the New York Edison Company controlling the supply of
the single-phase electrification of the N. Y. N. H. & H. R. R.

OIL CIRCUIT BREAKERS

143

Co. at that point. Fig. 89 is a 3000-ampere 3-pole type O-2
breaker.

FIG. 89. — Westinghouse type "O-2" oil circuit breaker.

Cells. — As the general type or cell construction for the E-6,
O-l, 0-2 breakers is identical, these three types or any two of
them can be readily assembled side by side in a symmetrical
structure. When it is considered possible that future growth
in a station may require larger breakers it is possible to put
up structures for the 0-2 breakers and slightly modify a type
O-l or E-6 breaker so that it can be arranged readily in the
larger structure. O-l breakers are installed in 0-2 structures
in the plant of the Buffalo General Electric Company, auxiliary
channel irons being utilized to take up the difference in width
between the two sizes.

The type O oil circuit breakers are particularly adapted to the
control of systems of large capacity from 40,000 up to 100,000
turbo-generator K.V.A. where voltages do not exceed 25, 000 volts.

This line supplements the type E line of cell mounting breakers,
providing higher current and interrupting capacities. These

144 SWITCHING EQUIPMENT FOR POWER CONTROL

breakers are supplied in single-pole unit form for cell mounting
only, each pole being mounted in a separate masonry compart-
ment. The operating mechanism is mounted on the top of
the cell structure on a channel and plate base, and operates the
several poles as a single unit.

Tanks. — The tanks are cylindrical in form, seamless, and
with rounded base, being die pressed from heavy sheet steel.
They represent the strongest form of tank construction possible.
Type O-l tanks are 16 inches in diameter, and type O-2 tanks
20 inches in diameter. These breakers are built in the following
sizes, all cell mounting, electrically operated only, in 2-, 3-, or 4-
pole forms.

RATINGS

Maximum

Amperes

Interrupting
Capacity

Type

60 cycle

25 cycle

Maximum
voltage

in arc
amperes
at rated
voltage

O-l

600

750

25,000

9,600

O-l

1 200

1 400

25 000

9 600

O-l
O-2
O-2
O-2

1,600
2,000
3,000
4,000

1,800
2,400
4,000
5,000

15,000
25,000
15,000
15,000

18,000
12,300
23,000
23,000

These breakers are electrically operated by the solenoid
mechanism mounted on the cell top. The breaker is closed by a
solenoid and is held closed by a hardened steel latch and a trigger
which engage automatically. The closing solenoid is regularly
furnished for use on 125-volt (normal) direct-current circuits
and has a standard operating range from 70 volts to 140 volts.
Coils for other than standard voltage with the same proportion-
ate operating range can be supplied on special order. Due to
the wide operating range, breakers with the standard coil can
be satisfactorily operated from 110- volt direct- current circuits.

Acceleration. — In all the type O breakers, an . accelerating
spring is provided as part of the complete breaker mechanism to
assist in forcing the breaker to the open position; an air cylinder
dashpot in the lower portion of the spring container takes up the

OIL CIRCUIT BREAKERS 145

shock of the moving parts. The action of this dashpot can be
adjusted by a screw needle- valve which regulates the size of
opening of the dashpot valve.

The high interrupting capacity rating of these breakers is
due to the form of tank, the use of steel supporting flanges with
steel bolts, steel tops, large volume and head of oil, liberally
designed arcing tips and the rapid acceleration of the moving
contacts when opening.

Oil gauges of the sight-glass form are supplied on each tank so
that proper maintenance of the oil level is assured with reason-
able degree of inspection. Drain valves are supplied on all
forms of this breaker so that when desired, the tanks can be
emptied before lowering.

Tanks. — The tanks are deep, providing ample space above the
oil level as an expansion chamber for the arc gases and to reduce
slopping of the oil from internal disturbances. The gases are
vented through specially designed check-valves, providing full
venting of gases, but at the same time preventing passage of oil.

Arcing contacts of the spring-actuated, butt type protect the
main current-carrying contacts. Each part can be easily re-
placed at little expense. The arcing contacts open only after the
main contacts have separated a considerable distance. As they
are placed outside the main contacts so that the magnetic blow out
effect of the current will blow the arc away from them, the
main contacts are fully protected from any possibility of arcing.

A modification of the design permits these breakers to be
made for frame mounting and the mechanism can be placed on
the floor at one side or in any of several different locations to
suit the desired arrangement of the station.

Specially wide spacing has been used in a few particular cases
where breakers were used with bus reactors and the pole spacing
was to match that of the reactors.

Type CO. — Where great compactness and high rupturing
capacity is desired the CO line can be used, these being essentially
O-l or O-2 poles with a simple compact mechanism something
like that of the type C.

The type CO oil circuit breakers in general perform on circuits
of not over 15,000 volts, the same service as the type O line,
but in more compact space. They have a unit-type electric
operating mechanism, forming part of an entirely self containing
breaker as shown in Fig. 90 which requires no intermediate
10

146 SWITCHING EQUIPMENT FOR POWER CONTROL

walls in the cell structure for supporting individual poles. The
complete breaker is shipped in one piece, except for the doors and
barriers, with all adjustments of contacts and mechanical parts
locked, thus reducing the installation work.

Comportments ifllo-ftrtt 0*

FIG. 90. — Westinghouse oil circuit breaker type COl.

Ratings. — The following sizes are built only in 3-pole elec-
trically operated cell mounting form.

Maximum Amperes

TVnp

Capacity

iype

60 cycles

25 cycles

volts

amperes
at rated
voltage

CO-1
CO-1

600
1 200

800
1 500

15,000
15 000

18,000
18 000

CO-1

1,600

2,000

15,000

18,000

CO-1

2,000

2,400

15 000

18 000

CO-2
CO-2
CO-2

600
1,200
1 600

800
1,600
2 000

15,000
15,000
15 000

23,000
23,000
23 000

CO-2
CO-2

2,000
2,400

2,400
3,000

15,000
15,000

23,000
23,000

Interrupting

OIL CIRCUIT BREAKERS 147

The type CO breakers are made for mounting in brick, concrete,
or steel structure compartments. The two outstanding features
of the type CO breaker are its compactness and its ease of
installation. No intermediate structure walls are required
for supporting the individual poles, all of them being supported
from the common steel top. The breaker is supported in the
structure compartment by means of anchor plates set in and
projecting from the cell walls. The steel top of the circuit
breaker rests on these anchor plates and bolts hold it securely in
place. The space between the circuit-breaker top and the floor
in front of the circuit-breaker tanks is covered with removable
doors. Three doors are furnished with each standard 3-pole
breaker. Each door consists of a metal frame with asbestos
panels and is hinged at the top to the mechanism base.

Type G. — The type G oil circuit breakers of modern design
comprise a complete line of high voltage breakers for indoor or
outdoor use. Four forms of these breakers are built, known as
types 'GA,' 'G-l,' 'G-2' and 'G-ll.' Each form has a different
interrupting capacity with corresponding differences in con-
struction.

The type G breakers all have the condenser type of terminal
bushings, steel tanks with welded seams, and large expansion
chamber with baffled vents for the arc gases.

All type G breakers can be had in automatic or non-automatic
forms. Automatic overload tripping can be obtained either
from separate current transformers or from bushing type current
transformers which are slipped over the breaker terminal bush-
ings.

Sizes. — These breakers are available for all voltages from
22,000 to 155,000 indoor or outdoor, manual or electrically oper-
ated. They are available for frame mounting up to and including
73,000 volts. With interrupting capacities of from 1440 to 5350
arc amperes per phase at rated voltage available with different
types, the requirements of present high voltage systems are well
met with this line of breakers. Practically all such breakers
are arranged for solenoid operation as 3-pole units and are
built with a separate steel tank for each pole of each breaker.
Usually these steel tanks are so arranged that their spacing
may be made to suit the wiring of the installation in case the
minimum spacing normally used with the breakers would intro-
duce undesirable bends in the wiring.

148 SWITCHING EQUIPMENT FOR POWER CONTROL

FIG. 91. — Westinghouse 37-K.V. oil circuit breaker type Gil.

FIG. 92. — Westinghouse 154-K.V. oil circuit breaker type GA.

OIL CIRCUIT BREAKERS

149

Indoor-outdoor. — All of the high tension breakers can be
made suitable for either indoor or outdoor service but are usually
supplied for outdoor, so most of the illustrations and descriptions
will apply to the outdoor type of equipment, but enough indoor
apparatus will be illustrated to show the essential differences
between the two types.

Up to 73 K. V. the high tension oil circuit breakers whether for
indoor or outdoor service are usually made frame mounting to
permit the tanks to be easily dropped to secure rapid inspection
and adjustment of the contacts.

Indoor. — Fig. 91 shows a 37-K.V. G-ll breaker for indoor
service and clearly illustrates the pipe framework used for
supporting the breaker at such a height that the tanks can be
readily dropped. The highest voltage breaker that has been
built for indoor service is shown in Fig. 92 which illustrates
the 154-K.V. type GA floor mounted breaker furnished to the
Big Creek Power Company a number of years ago.

FIG. 93. — Westinghouse type GA oil circuit breaker — contact details.

Quick Break. — Circuit breakers for high voltage service such as
these illustrated involve long travel of the contacts and heavy
moving elements and therefore are arranged to embody a special
quick break feature for the rapid separation of the arcing contact
which is so essential on a high power interrupting service.

Fig. 93 shows the contact details employed with the 154

150 SWITCHING EQUIPMENT FOR POWER CONTROL

K.V. breaker. The lower end of the condenser terminal bushing
is enclosed in a porcelain arc shield for protection from the arcs
that arise during operation. Between this arc shield and the
stationary contact is a metallic static shield for distributing
the stress uniformly over the surface of the terminal bushings.
The main contacts are of the butt type, each terminal having
two main contacts and two arcing contacts, the latter being
designed to take all of the arcing so that the main contact will
not become pitted or burned by the arc. The entire stationary
contact is enclosed in a metal hood which distributes the electro-
static stress that might otherwise be excessive due to the sharp
corners on the edges of the contact mechanism.

Arcing Contact. — The arcing contacts attached to the sta-
tionary terminals of the breaker are so arranged that in the
closed position they are latched in touch with the corresponding
arcing contacts on the movable member. When the breaker
opens the main contacts separate at once, but the latch holds the
arcing contacts together, forcing the upper one to be pulled
down against the compression of a spring for a distance of ap-
proximately 7 inches. After the moving member has dropped
the 7 inches, the latch releases and the spring retrieves the upper
arcing contact, breaking the circuit very quickly.

The break in the circuit occurs in the free oil and the natural
tendency of the gas bubble to rise is not in any way impeded.
The magnetic effect of the current passing down one stationary
contact across the moving member, and back the other stationary
contacts is such as to blow the oil away from the contact and
toward the side of the case. This effect together with the natural
tendency of the gas bubble to rise through the oil enables the arc
to be quickly carried away.

While the descriptions that follow apply to outdoor breakers,
corresponding indoor breakers differ only from the outdoor ones
in the omission of the rain shields from the condenser bushing
terminals and certain minor changes in the housing of the mech-
anism and the venting of the tanks.

37 K.V. — Fig. 94 shows a 400-ampere 37-K.V. 3-pole solenoid
operated frame mounted outdoor breaker with one tank removed
to show the contacts. This breaker has a guaranteed rupturing
capacity of 1700 amperes at 37 K.V. With the frame mounting
it is possible to drop the tank on any one pole to obtain ready
access to the contacts.

OIL CIRCUIT BREAKERS

151

FIG. 94. — Westinghouse type "G-ll" outdoor oil circuit breaker, 400 amps.
37 K.V.

FIG. 95. — Westinghouse type "G-ll" outdoor oil circuit breaker, 400 amps.,
73 K.V.

152 SWITCHING EQUIPMENT FOR POWER CONTROL

73 K.V.— Fig. 95 shows a 400-ampere 73-K.V. solenoid op-
erated outdoor frame mounting oil circuit breaker having a
guaranteed rupturing capacity of 2400 amperes at 73 K.V.
This breaker has elliptically shaped oil tanks made of. steel plate
with lap-welded seams and a cast steel top of domed shape to
secure ample strength against explosion. The tanks are ar-
ranged for suspension from the supporting frame and are hung
by suitable tie bolts connected to a supporting grid beneath
the tank. An overhung lip around the top is interlocked with
the tank rim and suitable packing between the top and the rim
insures waterproof joints. A suitable removable cover with
interlocking rim gives access to the upper portion of circuit-
breaker mechanism. Conduit pipe with packing washers and
lock nuts affords weatherproof communication from pole to pole
for the operating levers and for the control leads when required.
Solenoid operated mechanism is located at one end of the unit,
housed in a case or box with a removable cover having packed
joints. This box has conduit pipe for connection to the circuit-
breaker mechanism.

The steel top in addition to supporting and protecting the
operating mechanism is arranged to form an expansion chamber
to cushion the pressure caused at the instant of interrupting the
circuit. As considerable oil vapor and gas may collect in this
chamber, suitable baffled vents are placed in such positions as to
relieve sudden air pressures, and in addition, to induce circulation
of air through the chamber to drain out the accumulating oil
vapor. As the oil is of more or less volatile nature, this latter
function is of considerable importance. To prevent the trans-
mission of a disturbance in one tank to adjacent tanks and to the
box containing the operating mechanism and solenoid, suitable
baffles can be placed in the connecting conduit pipe. Pressure
can be vented to the outside, but propagation of pressure from
tank to tank will be prevented.

The terminal bushings are sufficiently protected by petti-
coated insulators to afford insulation under the most severe
conditions of driving rain, wet snow or sleet. It is not uncom-
mon to find the entire structure, including the exposed portions
of the porcelain insulators, incased in a coating of sleet, or to
see snow piled up practically to the entire height of the terminal
bushings.

OIL CIRCUIT BREAKERS

153

Frame Mounting. — On circuit breakers of small and moderate
size where the weight of the oil tanks and oil is not prohibitive,
the frame mounting arrangement of circuit breaker is highly
desirable as it permits the ready removal of the oil tanks for the
purpose of inspecting the contact details and the operating
mechanism without disturbing the line connections.

Platform Mounting. — Breakers for higher voltages and larger
rupturing capacities are usually made platform mounting owing
to the difficulty of lowering the tank filled with oil.

FIG. 96. — Westinghouse type "G-ll" outdoor oil circuit breaker, 400 amps.,
95 K.V.

With the larger breakers access to the interior of the tanks is
secured by the removal of the mechanism cap which exposes the
lever system and presents a sufficiently large opening to withdraw
any necessary part. The mechanism is ordinarily so arranged
that a terminal bushing complete with its contact details can be
withdrawn without disturbing any other details, and the moving
contact elements can also be withdrawn through the manhole
or mechanism cover.

Experience has indicated the desirability of providing a struc-
tural frame or platform that will permit access to the bottom of

154 SWITCHING EQUIPMENT FOR POWER CONTROL

the tank, allowing free air circulation as this assists in keeping all
parts free from rust and corrosion.

In certain cases the tank bases are made with openings in the
rim so that the bottom of the tanks can be painted with a long-
handled brush if the foundation is of concrete or masonry that
would otherwise make it difficult to get at the bottom of the
tanks.

Platform Type. — A typical outdoor platform mounted breaker
is shown in Fig. 96 which illustrates a 95-K.V. 400-ampere
breaker with elliptical tanks having a guaranteed rupturing
capacity of 2400 amperes at 95 K.V.

FIG. 97. — Westinghouse type "G-2" outdoor oil circuit breaker, 400 amps.,
135 K.V.

Type G-2. — The type G-2 oil breaker is of "all-steel construc-
tion" and has a tank of the strongest possible construction.
The shape of the tank is cylindrical with spheroidal top and
bottom, having the same radius of curvature as the sides. This
form of tank having all seams riveted is tested to withstand a

OIL CIRCUIT BREAKERS

155

static pressure of 150 pounds per square inch. The steel top
and bottom are flanged inside and riveted to the tank body,
completing a form of construction, all details of which are directly
comparable to that followed in the best high-pressure boiler
practice.

FIG. 98. — Westinghouse type "GA" outdoor oil circuit breaker, 400 amps.,
135 K.V.

This construction takes full cognizance of gas pressures which
accompany the interruption of high voltage large ampere capa-
city arcs. Of necessity these pressures are transmitted equally
through the surrounding oil medium to the walls of the containing
vessel. Due to the voltage and power of the arc, reliance is
placed on a large head of oil aiding the natural buoyancy of gas
bubbles to present an ever changing mass of cool and clean oil
to the arc while at the same time the mechanical strength of the

156 SWITCHING EQUIPMENT FOR POWER CONTROL

containing vessel is made ample to withstand pressures that may
be transmitted from the arc through the oil medium. Past
operating experience with high powered moderate voltage systems
has shown the danger involved in trying to confine this arc to
too small a vessel with a low head and small volume of oil.
This is particularly true when recognition is given to the demands
of modern operation for a breaker to be capable of opening its
rated interrupting capacity in arc amperes twice within an
interval of two minutes.

The large size of these circular tanks with the consequent
immense volume of oil, strength of materials and construction,
depth of contacts below the oil level and the rapidity with which
the contacts are opened, result in a breaker entirely adequate for
the largest power systems.

Fig. 97 shows a 400-ampere, 135-K.V., 3- pole breaker
having a guaranteed rupturing capacity of 4300 amperes per
phase at 135 K.V. This breaker was furnished to the West
Penn Power Company for 132-K.V. service and a modification of
it is available for 155-K.V. service

Type GA.— Fig. 98 shows the 400-ampere 135-K.V. electric-
ally operated oil circuit breaker having a guaranteed rupturing
capacity of 1600 amperes at 135 K.V. A number of these breakers
are in service in Michigan.

Designs have been prepared for breakers for use on 220-K.V.
circuits, and some are now being built.

CHAPTER V
RELAYS

Functions. — Modern distributing systems require protection
more selective and flexible than that afforded by the usual control
features of automatic circuit breakers and this need is supplied
by automatic devices known as relays which trip a circuit breaker
upon the occurrence of some predetermined change.

Types. — Relays are built to furnish protection on A.C. or D.C.
circuits against overvoltage, no voltage, overload, no load, reverse
load and reverse phase and such relays either directly or in con-
nection with other relays may be made instantaneous or provided
with a time limit either of definite duration or inversely propor-
tional to the extent of overload, etc.

Definite Time. — This type is used with circuits where the
service must be maintained at all hazards no matter how great
is the overload provided it does not last more than a definite
period of time say from 2 to 4 seconds, depending on the ability
of the system to withstand such conditions and the length of time
required for various feeder breakers to trip out, relieving the
system protected by the breaker with definite time limit.

Inverse Time. — This relay gives a selective action varying
inversely with the load so that usually the faulty line carrying the
heavier load will have its breaker tripped out before the other
breakers are affected.

D.C. RELAYS

Overload. — The D.C. overload relays of the Condit Electrical
Manufacturing Company are made with series coils in the form
of a solenoid for current ratings from 5-600 amperes as shown
in Fig. 99. For currents from 800-3000 amperes the magnetic
circuit is arranged to slip over a round stud while for currents from
800-8000 amperes the magnetic circuit can be put around the
copper strap connections in the leads or bus. These relays
are made as instantaneous or with inverse time limit features.

157

158 SWITCHING EQUIPMENT FOR POWER CONTROL

A modification of the arrangement is made by the addition of
the voltage coil that changes the relay to a D.C. reverse power
relay with the current element to slip over a circular stud.

FIG. 99. — Condit Electric & Mfg. Co. type "DC" relay.

Reverse. — When an adjustable reverse-current D.C. relay
with time limit is desired, a type of relay is used built on the
principle of a permanent magnet D.C. ammeter operated from
a shunt. In normal operation the armature of the relay tends to
turn in one direction but is restrained by a stop, while in the case
of reversal the armature turns in the opposite direction, its
movement being restrained by a spring and being proportional
to the strength of the current in the reverse direction.
The angle through which the armature has to turn to close the
contacts is adjustable by moving the stationary contact. The
inverse time element feature is obtained by the movement of the
aluminum frame, on which the armature is wound, in the intense
magnetic field, the eddy currents in the frame furnishing the

RELAYS 159

damping action. A modification of this design is used for D.C.
overload relay.

A.C. RELAYS

Overload. — One of the simplest overload A.C. relays designed
for instantaneous operation, definite time limit and inverse time
limit, consists essentially of a solenoid and core. In the in-
stantaneous relay the core lifts immediately and closes or opens
contacts that trip the circuit breaker when the current in the
coil reaches a certain value. With the inverse time limit the
movement of the core is opposed by a bellows with an adjustable
valve mounted above the coil. With the definite time limit the
same kind of bellows and valve is used but the solenoid does not
work directly on the bellows. When the overload occurs the
core rises instantly compressing a spring which in turn acts on
the bellows. If the core, due to continued overload, keeps the
spring in compression the required time, the air will be forced
out of the bellows and the tripping circuit operated. This type
of relay can be set for any time limit between 1 and 10 sec-
onds. Relays of this type are usually operated from current
transformers but are sometimes mounted on a high tension
insulator and connected in the high voltage circuit. This plunger
type of overload relay has been practically superseded by the
induction type.

Radial System. — The proper relaying equipment for use on
any A.C. line will depend among other things on the type of
distribution used. Where there is a single source of power with
feeders radiating out from the generating station and possibly
passing through one or more sectionalizing or transforming sta-
tions, proper selective action can usually be obtained by making
the breakers farthest from the power house practically instantar
neous in their operation, those at the power house being provided
with relays set for a definite time of from one to two seconds and
the intermediate sections being provided with relays having
various time settings.

Current Settings. — In addition to securing discrimination on
the part of the relays by means of a definite time feature, it is also
possible to discriminate by the current setting because trouble
which occurs at the far end of a branch line will not draw as
heavy a current as though it were closer to the source of power.
Selective action can frequently be obtained to advantage by the
use of an inverse time limit relay having characteristic curves

160 SWITCHING EQUIPMENT FOR POWER CONTROL

similar to those shown in Fig. 100. This type of relay has an
adjustable definite time element in addition to the inverse time,
and the combination of these two is well adapted for the protec-

800 1000 1200 1400

Percent Current Required to Close Contact!

FIG. 100. — Relay characteristic curves.

tion of circuits of this kind, because either the inverse time part

of the curve or the definite time part can be utilized, dependant

upon the particular circuit standard.

Type CO. — Such a combination of definite time and inverse

time is obtained in the type 'CO' Westinghouse relay shown in
Fig. 101. This relay is built on
the induction principle, and its
great success has been largely due
to its remarkable accuracy and
permanence of its calibration. The
use of a permanent magnet as a
time limit device, prevents over
swinging and chattering of the con-
tacts, and the construction is such
that the relay will instantly cease
FIG. loi.-westinghouse type its movement when the over load

CO definite minimum inverse time disappears.

limit overload relay. Torque Compensator.— One of

the essential features of this relay is the torque compensator
embodied in its design. This is essentially a small current
transformer having comparatively little iron in its magnetic
circuit so that it saturates at a little more than 5 amperes in
the primary. With this device the primary current can be

RELAYS 161

momentarily increased to 200 times normal without increasing
the secondary current more than a small percentage. As
it is this secondary current that actually works on the relay
mechanism the force of the relay is practically constant,
independent of the amount of the current, so that its speed of
operation is independent of the value of the short circuit and
is determined by the restraining influence of the permanent
magnet and the distance through which the contact has to move.
As this distance is adjustable, the definite time setting on the
standard relay can be made anything from 0.1 of a second up to
2 seconds, and in special cases up to 4 seconds. A current ad-
justment is also provided on the relay so as to secure normal
operation with relay current varying from 4 to 12 amperes.

Parallel System. — Where the distributing system instead of
being a radial one is provided with parallel circuits between the
generating stations and the points of distribution, such systems
can sometimes be protected satisfactorily by means of inverse
time element relays if the short circuit conditions are such that
relays of this type can properly discriminate, but the more usual
method of protecting service against trouble on parallel feeders
is to place reverse power relays at the substation end of each
feeder and definite time limit relays at the generator end.

FIG. 102. — Ring arrangement of circuits.

Ring System. — A modification of the parallel feeder arrange-
ment is the ring system where each substation is fed from two
directions, as indicated in Fig. 102. On such a system definite
time limit reverse power relays must be utilized and the time
setting of each successive relay should be increased by a
sufficient amount to allow time for the circuit breaker in the
preceding substation to open. On the diagram the time settings

162 SWITCHING EQUIPMENT FOR POWER CONTROL

of the various relays have been marked and for )£ -second time
interval will work satisfactorily if the relays are accurate and the
circuit breakers quick acting. Such a system becomes somewhat
more complicated if power is fed in at more than one point, as
for example if a generator ties in at station D. The adjustment
of the relays on such a system would have to be modified depend-
ing on whether the power was being generated at A or at D
so that it is evident that relays are desirable whose adjustments
can be quickly changed.

Reverse Power. — For the protection of a parallel feeder system
or a ring system, reverse power relays are necessary and these are
made by the Westinghouse Company in the form of a two ele-
ment relay, the current element being practically the same as
that of the 'CO,' and having the same overload and time ele-
ment characteristics. In addition to the current element there
is a watt element that closes a contact whenever the flow of
energy is in a reversed direction from the normal one. The cur-
rent element closes its contacts on excess current in either direc-
tion, but the relay will not function to trip the circuit breaker
unless the selective wattmeter element also functions due to the
power being in the reversed direction.

While in many cases transmission and distribution systems
can be readily sectionalized by the standard application of over-
load and reverse power relays, there are other conditions that
can best be handled by a balanced system of relays.

Balanced System. — This system, utilizing pilot wire schemes
and standard overload relays, operates from the secondaries
of current transformers placed at two ends of the feeder, but such
an arrangement requires conductors to be run between these
current transformers and, ordinarily, on long distance transmis-
sion lines, such an arrangement is not very practicable.

Split Conductors. — A split conductor scheme can often be
utilized to advantage where the power to be transmitted is such
as to required two conductors in parallel. In most cases, how-
ever, an arrangement of balancing relays on parallel feeders using
the cross connection of reverse power relays will work out to the
best advantage.

Balanced Relays. — Such an arrangement is indicated in Fig.
103, this showing four circuits between a generating station and
receiving station. This schematic diagram has been simplified
by showing only one phase on each of the feeder circuits. By

RELAYS

163

reference to these two figures it will be noted that the current
transformers at the generating station are connected in series for
each particular phase and similarly at the substation, and that
each relay, that must be of the reverse power (uni-directional)
type, is shunted across its own current transformer.

Generating Station

FIG. 103. — Balanced arrangement of relays.

Under normal conditions the load in each of the parallel feeders
will be the same, and since the relays have a higher impedance
than the current transformers, the current from the latter will
circulate through all of them in series without any flowing through
the relays. If the trouble occurs at any point outside the section
protected by the cross connected relays, the current over the
feeders will still be balanced and consequently there will be no
force tending to operate the relays. In other words, a short
circuit occurring on some other portion of the system will have no
tendency to trip out any of the breakers in this section.

On the other hand if trouble occurs at a point within the pro-
tected sections, the current over the defective circuits will be
higher than that in the others, and this excess current from its
current transformer must pass through the relays. While under
this unbalanced condition, current will flow through all of the
relays, it will be observed that the current is in the proper direc-
tion to cause the relays to act only at each end of the defective
section as shown by the arrows in the diagram.

Pallet switches are connected in the transformer secondary
circuit and are mechanically operated by the breaker so that
when the breaker opens the current transformers are short-

164 SWITCHING EQUIPMENT FOR POWER CONTROL

circuited. By this method, a feeder can be cut out of service
without interfering with the electrical balance in the current
transformer circuits.

Double Contact Relays. — Where there are only two parallel
feeder circuits, a double contact reverse power relay can be
utilized. This relay is so arranged that in case of trouble, the
watt element will close the circuit leading to the trip coil of the
breaker in the defective circuit, and the excess current element
will operate to trip out that breaker under suitable conditions
of overload and time element.

More complicated networks can usually be taken care of by
proper selection of the type of relays to be employed. It fre-
quently happens that the problem of automatic sectionalizing
can be very much simplified if, at the instant of short circuit, a
number of circuit breakers are opened for the purpose of simpli-
fying the operation of the remainder of the systems.

These induction type relays of the Westinghouse Company
have their characteristic curves marked on their nameplates.
The corresponding relays of the General Electric Company
have the information in the form of tabulated data on their
nameplates. All of these induction type relays utilize many of
the parts of the induction type watt-hour meters of the respective
makers.

The inverse definite time limit relays of the Condit Electrical
Manufacturing Company have many features similar to those
mentioned above, except that they do not use any power con-
suming retarding element, such as bellows, dashpot, magnetic
drags, etc. The current adjustment is obtained by means of a
calibrated compression spring and the time adjustment is
obtained by moving the contact arm into various positions on
the worm wheel.

The usual sectionalizing relays are intended for disconnecting
defective feeders and are not primarily intended to protect
apparatus in case of overload. The current settings of such
relays are generally a function of the current flowing under short
circuit and are thus higher than required for protection against
sustained overload.

Temperature Relay. — This may be used to protect any alternat-
ing current apparatus from excessive heating if the apparatus is
so arranged that exploring coils can be installed. The relay
is intended to protect apparatus against overheating from sus-

RELAYS 165

tained overloads. To afford this protection with the least
interruption of service the breaker should be tripped through
the direct effect of the temperature of the apparatus. The
relay should be so arranged that it prevents the breaker from
tripping if the overload is of such short duration that the tem-
perature does not rise to a dangerous value; while, if the overload
persists, the breaker must be tripped out as soon as the tempera-
ture rises beyond the critical value. This is accomplished as
follows :

Principles. — The temperature relay operates on the Wheat-
stone bridge principle. Two arms of the bridge are copper
exploring coils arranged to be placed in the oil or embedded in
the windings of the apparatus to be protected, the other two
arms are unchanging resistance mounted in the relay. The
current for the bridge is supplied by the current transformer
connected in the circuit of the apparatus to be protected. The
relay has two windings, corresponding to and co-operating to
produce torque in a manner similar to the current and voltage
coils of a wattmeter. The main winding is a coil operated
directly by the current transformer. The auxiliary coils are
connected to the Wheatstone bridge arms similarly to a galvano-
meter connection, and thus receive current the magnitude and
direction of which depends upon the resistance of the search coils.
Above a certain temperature the torque of the relay is in the
contact direction and below, in the opposite direction. It will
thus be noted that, in order to close the contact, two predetermined
conditions must co-exist: excess current, and excess temperature.
Neither one will separately trip the relay.

Transfer Relays. — These are used with protective relays that
operate on excess current where a direct-current trip circuit is
not available. They energize the trip coil of the circuit breaker
through current transformers.

The breaker operates solely through the current transformer
and the relays. When there is no fault on the line the trip coil
of the breaker is mechanically and electrically isolated from the
circuit, avoiding possibility of tripping due to imperfection in the
relay contacts ordinarily shunting the trip coil.

The relay contains two series coils, an upper or operating coil
and a lower or holding coil (see diagram of connections, Fig. 104).
The holding coil holds down the armature core, until a third coil,
wound on the same magnetic circuit and known as the releasing

166 SWITCHING EQUIPMENT FOR POWER CONTROL

coil, is short-circuited by the protective relay. The releasing
coil acts as the secondary of a transformer and when short-cir-
cuited, a current flows through it, demagnetizing the core. The
holding coil, therefore, allows the operating coil to raise the core
which operates the transfer switch, thus closing the trip coil
circuit.

FIG. 104. — Transfer type relay.

The transfer switch and other current-carrying parts of the
relay are designed to carry 5 amperes continuously, but during
time of short circuit the switch may be called on to handle as
much as 100 or 200 amperes.

A current transformer must be selected of sufficient capacity to
operate the protective relay, the transfer relay, and the trip coil.
Low ratio bushing type current transformers sometimes used on
high voltage circuit breakers are not suitable.

Only one trip coil is required for use on a polyphase circuit, but
if the breaker is equipped with as many trip coils as there are
relays, it is advisable to connect each trip coil to its corresponding
relay.

Bell Relay. — This provides an alarm to notify the attendant
that a circuit breaker has tripped automatically. It is generally
mounted behind the switchboard. This relay operates the alarm
when the tripping is due to the action of automatic tripping
devices, but does not operate when a circuit breaker is opened
intentionally. The alarm can consist of a bell or other indicating
device. The relay action is such that the alarm continues until
stopped by pushing a button.

The bell relay consists of a contact-making armature actuated
by an electromagnet excited by two windings. One winding

RELA YS

167

is in series with the automatic trip circuit. When automatic
tripping occurs, current passes through this winding and the
armature is attracted, closing the bell circuit. The other winding
is in parallel with the bell circuit, so that when the bell circuit is
closed this second winding holds the armature and does not
permit the circuit to open when the trip circuit has opened with
the circuit breaker. The bell circuit is opened by means of a
push button provided for this purpose, whereupon the armature
of the relay opens contact.

B A

To-f Operating Bus.

To Opening Wire
Gen Oil Switch.
Vfre
itch.
To Opening Wire
Of uuy other Switch
which it may be
desirable to Open.

FIG. 105. — Schweitzer & Conrad multi-circuit relay.

S. & C. Relay. — The multiple circuit sensitive relay of
Schweitzer and Conrad is used where it is desirable to have a
relay that will operate on very small currents and yet have con-
tacts that will carry sufficient current to operate remote-control
circuit breakers, field circuit breakers, blower motor circuits and
the like. This is accomplished by having a relay provided with
a weighted arm that has its weight just beyond the center so that
very little energy is needed to carry it past the center and allow it
to fall into the position where it will close the necessary number of

168 SWITCHING EQUIPMENT FOR POWER CONTROL

auxiliary circuits. This type of relay can be used to advantage in
connection with the Merz-Price system of differential protection.

With this scheme, the relays are connected between the three-
phase pilot wires and the neutral pilot wire connecting the
secondaries of the neutral current transformers to the secondaries
of the terminal current transformers. The relays are connected
at the electrical centers of the pilot wires. The balancing resis-
tances shown in the diagram are necessary in order to be able to
connect the' relays to the pilot wires at the electrical center, as
in most cases it would be impractical to connect them midway
between the two sets of current transformers.

Connections. — The scheme of connections shown in Fig. 105
provides for only three relay contact circuits. A favorite ar-
rangement with large generators is to use a four-circuit relay to
open the two generator oil circuit breakers, the field circuit
breaker and blower motor circuit breaker.

With the circulating current system of generator protection the
relays are not affected by an unbalance of current in the different
phases, or by overloads and external short circuits no matter how
great, or by reverse power, provided the connections are made as
shown and the balancing resistances are of the proper value. In
other words, the relays will operate only in case of a ground or
other fault occurring in the generator windings or on the leads
between the neutral current transformers and the terminal
current transformers. Furthermore, they will operate on such
small currents and so quickly that they will disconnect the
generator from the system and open the field circuit before
material damage is done at the point of breakdown and with a
minimum of disturbance to the system itself.

Series Relay. — In high voltage stations requiring overload
protection and where the extra cost of separate current trans-
formers has prohibited the use of accurate relays, the high voltage
series relay shown in Fig. 106 has been an economical substitute
affording ample overload protection and an approximate time
element. These relays have been used chiefly for circuits of 100
amperes or less; for heavier currents the use of ring type current
transformers built around the circuit breaker bushings and op-
erating induction relays will be found more convenient. Series
relays are for indoor use and are suitable for any frequency.

The relay coil is inserted in the high voltage line, but the
contacts and timing parts are insulated and can be handled,

RELA YS

169

adjusted, or tested without disconnecting the feeder. The coil
can be mounted on a disconnecting switch or choke coil without
separate insulators, and the contact mechanism mounted in
the position most convenient. A solenoid mechanism operates
a timing and circuit-closing element through a wood rod or
micarta chain of such length
as to provide ample insula-
tion for the voltage in use.

Two forms of series relays
are furnished: inverse time
element and definite time
element. The inverse time
element relay can be set for
practically instantaneous
tripping.

Inverse Time. — In this re-
lay the solenoid and chain are
opposed in their motion by
a bellows with an adjustable
valve. The valve has a small
numbered dial which permits
of any setting between a
maximum time element of
about 20 seconds at 25 per
cent, overload and a mini-
mum of about 1 second at
the same overload. With
greater overload the relay
acts in a shorter time.

Definite Time. — In this relay the same kind of bellows and
valve are used as for the inverse time element, but the solenoid
chain does not act directly on it. The core and chain rise
instantly when the current reaches the tripping valve, and
compress a spring. The spring in turn acts on the bellows. If
the overload continues for the time for which the relay is set
the tripping contacts close. The time required for the spring
to close the contacts depends only on the setting of the valve,
and is entirely independent of the magnitude of the overload.
The relay can be set for any time element between 1 and 10
seconds.

The minimum current at which the relay will trip depends

FIG. 106. — Series type of relay.

170 SWITCHING EQUIPMENT FOR POWER CONTROL

on the number of weights placed on the arm of the contact
making mechanism. This can be varied from 80 per cent, to
160 per cent, of the rated current of the relay.

These relays are not as accurate as to time element as the
magnetically damped relays. Their time element will be found
sufficiently accurate to afford protection on the circuit to which
applied, but selective protection with regard to other circuits in
the system cannot always be satisfactorily obtained with a
bellows relay.

The circuit breaker should have auxiliary contacts to open the
trip circuit when the breaker opens, reliev-
ing the relay contacts of this duty.

One relay is required to protect a single-
phase circuit, two relays for a 2-phase or
3-phase ungrounded neutral circuit, and
three relays for a 3-phase grounded netural
circuit.

An insulating support for the relay
element is not furnished separately as the
relay is intended to be mounted on the
disconnecting switch pillar or other support
of the high voltage line. Where required
a bracket support complete with insulator
and necessary mounting plate can be
supplied.

High Voltage Induction. — Fig. 107 shows
the latest modification in this type of equip-
ment where the series solenoid is replaced
by a low voltage series transformer, an
accurate induction type relay and a transfer
type relay, all of these devices being
mounted on a small panel, the latter being
supported by a high voltage insulator. The current transformer
and induction relay permit very accurate relay settings with ad-
justable definite time delay from 0.1 to 2 seconds, and current
settings from 4 to 12 amperes. The operation of the induction
relay serves to close the circuit of the releasing coil of the transfer
relay. This transfer relay is connected through a micarta in-
sulating chain to the switch whose contacts, on closing, cause
the electrical tripping of the breaker.

With certain changes this type of relay has been made suitable
for outdoor high voltage service.

FIG. 107. — Westing-
house high voltage
induction type relay.

CHAPTER VI
SWITCHBOARD METERS

While this chapter deals particularly with instruments, their
detail design will not be touched on but some general information
will be given relative to meters and their various functions in
connection with switchboards.

Compactness. — This is one of the essential features of switch-
board meters owing to cost of panel space, reduction in attendance
and visibility of all instruments from one point of operation.
While securing compactness, length of scale has not been lost
sight of in design and this length of scale varies greatly in instru-
ments of different designs occupying approximately the same
amount of space.

Accuracy. — While this is of great importance it is necessary
to distinguish between the accuracy that is desired in laboratory
instruments and the accuracy which can be obtained in switch-
board meters without sacrificing other essential qualities such
as ruggedness, sensibility and accessibility. For switchboard
work it is better to secure instruments that will stay accurate
within 2 per cent, with an initial error of 1 per cent, than to
use meters whose initial error is only a small fraction of 1 per
cent, but which will not remain within 2 per cent, when used in
actual switchboard work where the magnetic stresses resulting
from system short circuits are apt to damage a very sensitive
meter. High accuracy and ruggedness are more or less antago-
nistic qualities and a satisfactory compromise is an initial error
of about 1 per cent, and a final error in actual service of less
than 2 per cent.

D.C. Meters. — For direct-current service the cheaper grades
of meters are made of the moving iron type while the better
grade of ammeters and voltmeters are of the D'Arsonval per-
manent magnet construction. When the meters are so designed
that the movements can be readily removed without disturbing
the magnetic circuit by the removal of the pole pieces they are
particularly suitable for switchboard service.

171

172 SWITCHING EQUIPMENT FOR POWER CONTROL

A.C. Meters. — For A.C. service the indicating instruments are
made as "moving iron," "moving coil" or "induction" type
and the relative advantages and disadvantages of these types
are as follows:

Moving Iron. — This electromagnetic type of meters has
good initial accuracy and is approximately free from tempera-
ture and frequency errors and is easy to repair. Unless
heavily shielded they are subject to external fields and their
scale length is short.

Moving Coil. — This electrodynamometer type is free from
errors due to temperature and frequency variation and can be
made with very high initial accuracy. They are usually delicate
and difficult to repair, have short scale lengths and are subject
to external fields of same frequency unless heavily shielded by
internal laminated iron shields.

Induction Type. — These meters have good initial and service
accuracy, rugged and simple movements, extremely long and
easily read scales and are easy to repair. The frequency error is
greater than in the other types and they are subject to slight
errors from external fields only when of the same frequency and
in certain directions.

D.C. Ammeters. — Direct-current ammeters of the moving
iron type are built for connecting directly in the circuit in capaci-
ties up to about 600 amperes while the permanent magnet
meters are made in all capacities and are usually operated from
shunts having a drop of approximately 50 millivolts.

D.C. Voltmeters. — D.C. voltmeters of any type are connected
directly across the circuit in series with a resistance or are con-
nected across a portion of the resistance in such a way that their
scale reading gives a correct indication of the pressure. As
most D.C. plants whether for railway or for light and power
service are operated at practically constant potential the volt-
meters are depended on as a guide to the operators in maintaining
the proper pressure.

A.C. Voltmeters. — These are usually wound for connecting
directly to the circuit for pressures up to approximately 750
volts and beyond that point are operated from voltage trans-
formers usually with a 100-volt secondary. These voltmeters
are frequently marked with scale corresponding to primary volt-
age of the transformers, and have coils that will stand 150
volts. For example, the voltmeter used with the 6600-volt cir-

SWITCHBOARD METERS 173

cuit would probably be operated from a transformer having a
ratio of 6600-110 volts and would be provided with a scale of
9000 volts.

A.C. Ammeters. — Certain types are made in capacities up
to about 300 amperes for connecting directly in the circuit
unless the voltage is high, but the better grades of instruments
are operated from current transformers usually having a sec-
ondary current of 5 amperes. The scale reading of the meter is
usually made to correspond with the primary capacity of the
current transformer. Arrangements can usually be made so
that one A.C. ammeter can be operated from any number of
current transformers, so as to read the current in any circuit.

Wattmeters. — On A.C. generator panels and sometimes on
other panels of a switchboard, indicating wattmeters are desirable
to show at a glance the output of that particular circuit indepen-
dent of the voltage or power factor of the circuit. They are
particularly useful on A.C. generator panels to facilitate the
proper division of the load. On panels for use with synchronous
motor-generator sets or tie circuits which may either be taking
power from or delivering power to the bus bars, double reading
wattmeters with the zero in the center of the scale are recom-
mended.

Watt-hour Meters. — On feeder and load panels and sometimes
on generator panels it is often deemed advisable to install watt-
hour meters either A.C. or D.C. to record the power supplied to
a certain feeder, to one set of bus bars or furnished by one genera-
tor. A.C. watt-hour meters can be provided with a recording
demand chart to give readings every 15 minutes.

Power Factor. — On panels for control of the A.C. end of
synchronous converters and synchronous motors it is advisable to
install power factor meters or reactive factor meters as these
instruments will show at a glance whether the fields have been
adjusted to best advantage or whether the current taken is
leading or lagging in character. As the pointer on one design
of the power factor meter can move through an arc of 360 degrees
it can indicate whether the circuit in which it is connected is
delivering power to or taking power from the bus and whether the
current is leading or lagging.

Field Ammeters. — These are often supplied for use in con-
nection with generator and synchronous motor circuits to aid in
the proper adjustment of the field.

174 SWITCHING EQUIPMENT FOR POWER CONTROL

Frequency Meters. — These can often be used to advantage to
determine the frequency at which the plant is operating. Where
there are two or more sets of bus bars, or several stations feeding
into a common transmission line this point is often of vital
importance.

Synchronoscopes. — On the better class of A.C. boards it is
usual to supply synchronoscopes instead of depending on lamps
for synchronizing. These instruments of General Electric
or Westinghouse make are so made as to actuate a hand moving
around a dial in such a manner that the angle between the pointer
and the vertical indicates the phase angle between the E.M.F.
of the bus bars and the machine to be connected. If the fre-
quency of the incoming machine is too high, i.e., if the machine
is running too rapidly the pointer will revolve in the direction
marked "fast" while if the machine is not running rapidly enough
the pointer will revolve in the direction marked "slow."

The synchronoscopes of the Weston Electrical Instrument
Company are built on a different principle resulting in the ap-
parent movement of the hand across the scale in one direction or
the other corresponding to the "fast" or "slow" direction with
the pointer stationary at the middle of the scale at the instant of
synchronism.

Static Ground Detectors. — For higher voltages static ground
detectors are recommended. The Westinghouse types are
operated from condensers so that there is no danger from high
voltage in the instruments, in case of accidental contact. With
the General Electric device, rods of high resistance material
limit the current to an inappreciable amount in case of accidental
contact.

Graphic Meters.— In addition to the indicating meters de-
scribed above various manufacturers furnish D.C. ammeters and
voltmeters as well as A.C. ammeters, voltmeters, wattmeters,
power factor meters and frequency meters that plot a graphic
chart either as a circular chart with polar co-ordinates or on a
continuous strip with rectilinear co-ordinates. In the first
case circular charts about 8 inches in diameter are used, revolving
once an hour or once a day or at some other predetermined rate
while with the latter type the scale on the chart moves at 2,
4, 8 inches per hour or at any other desirable speed and a record
for a month or so can be made on a continuous strip of paper if
desired.

SWITCHBOARD METERS
GENERAL ELECTRIC INSTRUMENTS

175

Horizontal Edgewise. — The indicating instruments of the
General Electric Company are made in various forms but the
usual design for use on large A.C. switchboards is the horizontal
edgewise arrangement illustrated in Fig. 108. These instruments

FIG. 108. — General Electric Co. horizontal edgewise meter.

are about 6^ inches high, 8 inches wide and all of the usual types
of indicating meters both A.C. and D.C. are made in this form,
presenting a very uniform appearance on a switchboard. The
A.C. meters are operated from current and potential trans-
formers and the D.C. ammeters either
direct in the circuit for moderate
capacities or operated from shunts in
the larger sizes. These meters are
very substantial in their construction
and withstand well the short-circuit
stresses met with in actual station
operation.

Round Pattern. — Round pattern
meters are made as ammeters and
voltmeters for A.C. and D.C. service
in two sizes, one about 9^ inch and
the other 7>^ inch diameters. The D.C. instruments work on
the D'Arsonval principle, while the A.C. instruments work on
the Thomson inclined coil principle, the appearance of these
meters being as shown in Fig. 109.

D. C. Watt-hour Meters. — All G. E. direct-current switchboard
watt-hour meters are essentially high torque devices. Friction

FIG. 109. — General Electric Co.
round pattern meter.

176 SWITCHING EQUIPMENT FOR POWER CONTROL

is reduced to lowest value and ratio of torque to friction is maxi-
mum, insuring long life with continued accuracy. The design
of the commutator and bearings is such that the possibilities
of increased friction due to age and wear are minimized, hence the
ratio of torque to friction increases, which is the real criterion of
the accuracy of a meter, is very large.

Having no iron in armature or field circuits, no considerations
of magnetic saturation are involved. Therefore, meters have
straight-line characteristics even to point of physical destruction.

The armatures of the D.C. watt-hour meters are spherical
and move in a circular field. This secures highest torque with
lowest watt loss, the greatest possible number of magnetic lines
being cut by the armatures. Their astatic arrangement mini-
mizes effect of stray fields since any magnetic field tending to
weaken the torque of one armature strengthens torque of the other.

A.C. Watt-hour Meters. — These meters for switchboard
service are rectangular in shape and provided with metal cover
or glass cover and arranged for single phase or polyphase service.
These meters are provided with testing terminals that allow
testing meters to be cut into the circuit or the meter winding
isolated without interrupting the circuit or without going behind
the switchboard. The corresponding house meters for single
phase or polyphase service are provided with metal covers.

Round pattern curve drawing instruments are provided with
electrical elements of the solenoid type, direct acting with gravity
control. Charts are circular 8-inch diameter with a chart speed
of one revolution in either 12 or 24 hours, but other speeds can
be furnished.

Large graphic meters with a rectangular chart about 5 inches
wide and a paper speed of 3 or 6 inches per hour can be supplied
as ammeters, voltmeters, indicating wattmeters, power factor
meters, frequency meters, etc.

BRISTOL, ESTERL1NE, DUNCAN, SANGAMO METERS

A complete line of graphic instruments are made by the Bristol
Company embracing the usual ammeters, voltmeters, and watt-
meters, as well as recording thermometers, pressure gauges and
other similar devices. The Esterline Company build graphic
instruments of all kinds, while shunt type D.C. watt-hour meters
are made by the Duncan and by the Sangamo companies. Space
does not permit a description of them.

SWITCHBOARD METERS 177

THE ROLLER SMITH COMPANY

The Roller Smith Company make indicating instruments in
various sizes and shapes for D.C. and A.C. work to measure
current, voltage, etc.

For direct-current work for batteries and automobile work,
ammeters up to 100 amperes and voltmeters up to 150 volts are
made with an over-all diameter of 3^ inches and body diameter
of 2% inches in either the protruding or flush styles of mountings.
These instruments are of the permanent magnet moving coil
type with light but rigid moving elements. These are known as
"Junior Imps. "

The 4-inch Imps are made as ammeters up to 200 amperes and
as voltmeters up to 300 volts. These instruments are 4 inches in
diameter of the moving coil type.

Junior and 4-inch Imp instruments are made as A.C. ammeters,
voltmeters and single-phase wattmeters. The ammeters and
voltmeters are of the electromagnetic type while the single-phase
and D.C. wattmeters are of the electrodynamometer type. A
very efficient air damping scheme is used.

The standard D.C. switchboard ammeters and voltmeters
are made in 7^-inch and 9-inch round pattern protruding or
flush type and illuminated dial. These meters can be furnished
with the usual ranges and are all of the permanent magnet mov-
ing coil D'Arsonval type. Horizontal edgewise ammeters and
voltmeters can also be furnished.

A.C. instruments can be supplied in the 7^-inch and 9-inch
round patterns and illuminated dial types, the mechanism being
the electromagnetic type air damped for the ammeters and volt-
meters. Ammeters and voltmeters can also be supplied in the
horizontal edgewise construction. Power factor meters, fre-
quency meters, indicating wattmeters, synchronoscopes and
ground detectors can also be furnished.

Recording Synchronoscope. — A recording device made by
Schweitzer and Conrad, for attaching to a synchronoscope consists
essentially of a paper holding and shifting device, and insulated
ring in the synchronoscope dial and a spark coil or vibrator. A
continuous ribbon of paper is fed from a metal spool on the left
along guides and across the upper half of the synchronoscope dial
to the spool on the right.

The dial plate of the ordinary synchronoscope is replaced by
one of insulating material having a brass ring set in flush with its
surface. The ring has a radius a little less than the length of the

178 SWITCHING EQUIPMENT FOR POWER CONTROL

instrument pointer and is furnished with an insulated stud extend-
ing through the back of the indicator case. To the under side
of the pointer and directly in line with the ring is attached a
platinum point.

One of the leads from the spark-coil secondary is connected to
the insulated stud, and the other to a stud screwed into the instru-
ment case and therefore is in electrical connection with the
pointer. The primary leads are connected to a direct-current
source, such as the exciter or operating bus, through an auxiliary

Bemoved.' From To Oil

Pot. Trans. Switch

FIG. 110. — Connections of Schweitzer & Conrad record synchronoscope.

contact the location of which depends upon the scheme of control
wiring. The purpose of the auxiliary contact is to close the
circuit to the spark-coil primary simultaneously with the closing
of the control switch and to keep it closed until opened by the
operator.

The connections of this device are shown in Fig. 110. With
the energizing of the spark coil at the time the control switch is
closed, a succession of sparks jump from the insulated ring to the
electrode on the pointer, puncturing the paper ribbon and so form-
ing the record. For a perfect operation the record will be a very
short row of quite large punctures. These will be all on one

SWITCHBOARD METERS 179

side of the synchronous position if the machine was running
faster than the system frequency and all on the other side if slower.

WESTINGHOUSE INSTRUMENTS

As typical of a complete line of instruments, the various types
made by the Westinghouse Electric & Manufacturing Company
will be enumerated in considerable detail.

Small D.C. — For automobile service the type El ammeters
have 2-inch dials and IJ^-inch scales, while the type EW instru-
ments are made as ammeters and voltmeters with 3-inch dials
and 2%-inch scales.

Type El. — This instrument utilizes the polarized vane con-
struction, comprising a moving soft-iron vane polarized by
a stationary permanent magnet and deflected over its scale by the
action of a stationary current coil. No springs or moving coils
are used, thus resulting in great simplicity and ruggedness. The
indications are made deadbeat by means of an efficient damper.

Type EW. — The instrument operates on the D'Arsonval
principle, involving a permanent magnet and a moving coil, with
spiral current-carrying springs, mounted in pivot and jewel
bearings; the movement being rendered deadbeat by winding the
moving coil on an aluminum damping frame.

Both types of these meters are mounted in open-faced circular
pressed-metal cases arranged with a flange for flush mounting.

For use where small size is essential, the types BX, AW, EH
and FW instrument designs are well adapted.

Type BX. — These instruments for direct current or alternating
current of any frequency have 2-inch dials, 2-inch scales and they
may be used for the measurement of small direct currents, such as
the filament and plate currents of radio communication sets, or on
farm-lighting or other small charging and lighting panels, or in
dental, electro-medical, or other applications where space,
economy and accuracy are essential.

Type BX instruments operate on the D'Arsonval principle.
By combining the millivoltmeter with a noninductive heater and
thermocouple it is made suitable for the measurement of high
frequency alternating currents such as are encountered in radio
communication. The same instrument may also be operated
on alternating-current circuits of commercial frequency.

Type AW. — The type AW switchboard instruments for direct
current are 3 inches in diameter with 2%-inch scales and are

180 SWITCHING EQUIPMENT FOR POWER CONTROL

especially suitable for use on small direct-current switchboard
panels, such as battery charging, generator and control panels
for marine, dental, telegraph, telephone and farm lighting
equipments. The D'Arsonval type of movement is employed,
using a case with a round open-face, glass cover, with rear mount-
ing studs, stamped metal case and rim.

These instruments are guaranteed to be correct within 2 per-
cent of full scale at all parts of the scale, and are 3^ inches in
diameter over all and project 1% inches from face of panel;
studs suitable for panels up to % inch thick.

Type FW. — The type FW switchboard instruments for direct
current are 5 inches diameter with 4-inch scales and are similar
in main features to the type AW.

FIQ. 111. — Westinghouse D.C. instruments — comparison white and black dials.

Seven-inch Meters. — For most of the important switchboards
built by the Westinghouse Company they utilize the 7-inch
diameter meters known as type SL for D.C. service and SM, SI, or
SD for A.C. These meters are made either with the usual white
dials and black figures or with black dials having white figures.
The relative legibility of the two different types of dials with the
same illumination is shown in Fig. Ill, where a lamp directly
above and between two meters is provided with a half shade to
throw the light directly on the dial of each meter.

D.C. INSTRUMENTS

Type SL. — These switchboard ammeters and voltmeters for
direct current are intended for the most general switchboard
applications, wherever highest grade instruments are required.
Their cases are of soft iron, easily removed, the base remaining
on the panel, and they are provided with covers of flat glass
rendering the entire pointer visible; this makes it easy to take

SWITCHBOARD METERS 181

readings from a distance and from any angle. The scales are
approximately 7 inches long and the meters operate on the
D'Arsonval principle, but have a moving coil operating in a
single air gap. The complete movement is readily removed for
repairs. The single air gap construction makes it possible to
remove the moving coil without first removing the pole pieces and
without disturbing in any way the magnetic circuit.

Voltmeters. — The resistance of the voltmeters is approximately
50 ohms per volt up to 750 volts. For higher voltages the
resistance is 100 ohms per volt. The accuracy is 1 percent of
full scale at points between % and % scale, and average accuracy
2 percent of full scale at other points. These instruments have
an over-all diameter 7^6 inches; depth from switchboard, 4
inches.

Ammeters. — With the exception of the self-contained styles,
type SL ammeters operate from shunts and give full scale de-
flection with 50 millivolt drop at the terminals of the shunt.

Pyrometry rmllivoltmeters for use with thermo-electric couples
can be adjusted for 20 to 100 millivolts, full scale. The current
required at full scale is 0.01 amperes. The scale can be cali-
brated in millivolts or degrees.

For temperature indicators voltmeters arranged as resistance
type temperature indicators, complete with coils or bulbs, can be
furnished for reading the temperature of machinery, ovens, etc.
The scale can be calibrated in volts or degrees.

Type SM. — The A.C. instruments, switchboard ammeters,
voltmeters and wattmeters for alternating current have an
over-all diameter of 7%6 inches; depth from switchboard
4 inches (the polyphase wattmeter requires hole 7^6 inches
diameter through panel) with 14^-inch scales.

Type SM instruments operate on the induction principle,
with two A.C. fields so displaced that they produce a rotating
magnetic field that causes an aluminum drum to tend to rotate.
This tendency to rotation is opposed by a spiral spring.

The complete movement is readily removed for repairs. The
moving element consists of a light drum and a pointer, both of
aluminum, mounted on an aluminum shaft, with removable
steel pivots.

The ammeters and voltmeters are guaranteed to be correct
within 1 percent of full scale at all points of the scale; the

182 SWITCHING EQUIPMENT FOR POWER CONTROL

wattmeters within 2 percent. The general appearance of this
meter is shown in Fig. 112.

Type SI. — Other instruments of the induction type operating
on a somewhat different principle are the type SI power factor
meters, reactive factor meters and synchronoscopes, the power
factor meter being shown in Fig. 113. These operate on the
rotating field principle. In the rotating field produced by coils
connected to the metered circuits there is pivoted a movable
iron vane or armature, magnetized by a stationary coil the current
for which is taken from a current transformer in one phase of
the circuit. As the iron vane is attracted or repelled by the
rotating field, it takes up a position where the zero of the rotating
field occurs at the same instant as zero of its own field. Thus
its position indicates the phase angle between the voltage and
current of the circuit.

FIG. 112.— Westing-
house type S.M. A.C.
ammeter.

FIG. 113. — Westing-
house power factor in-
dicator.

In the 3-phase instrument the rotating field is produced by
three voltage coils spaced 120 electrical degrees apart; and in
the single-phase instrument by means of a split phase winding
connected to the voltage circuit.

The instruments are enclosed in round, dust-proof cases.
There are no movable coils or flexible connections and no springs
are used to control the movement. The construction is, therefore,
extremely simple and rugged. External fields can not influence
the readings.

Synchronoscope. — The type SI synchronoscope indicates by
means of a pointer, which assumes at every instant a position
corresponding to the phase angle between the E.M.Fs. of the
bus bars and the incoming machine. It gives exact indications

SWITCHBOARD METERS 183

and pointer is continuously visible during both the dark and
the light periods of the synchronizing lamps.

The principle of operation is a rotating field produced by
current from the bus bars passing through a split phase winding
and two angularly placed coils. In this rotating field is a mov-
able iron vane, or armature, magnetized by a stationary coil
connected across the incoming machine. The iron vane takes
a position where the zero of the rotating field occurs at the same
instant as the zero of the stationary field. Thus its position at
every instant indicates the phase angle between the voltage of
the incoming machine and that of the bus bars. As this angle
changes, due to difference in frequency, the iron vane with the
pointer attached to it rotates, and when synchronism is reached
it remains stationary.

Frequency Meter. — Still another induction type instrument is
the type SD switchboard frequency meter. The instrument,
which operates on the induction principle, consists of two volt-
meter electromagnets acting in opposition on a disk attached to
the pointer shaft. One of the magnets is in series with a reactor
and the other with a resistor, so that any change in the fre-
quency will unbalance the forces acting on the shaft and cause
the pointer to assume a new position where the forces are again
balanced. The aluminum disk, acted upon by the magnets, is
so arranged that when the shaft turns in one direction the torque
of the magnet tending to rotate it decreases, while the torque
of the other magnet increases. The pointer, therefore, comes to
rest where the torques of the two magnets are equal. This
arrangement insures freedom from error due to varying voltage.

Illuminated Dials. — Where illuminated dial instruments are
wanted they can be supplied for either D.C. or A.C. service.
The direct-current instruments operate on the D'Arsonval prin-
ciple and alternating-current instruments on the induction prin-
ciple. The movements are similar to these of the corresponding
round type instruments. The scales are 15^ inches long, and
are made of translucent material, illuminated from the rear by
two 110- volt 6-candlepower tubular lamps.

The D.C. voltmeters and ammeters are guaranteed correct
within 1 percent of full scale at all points. The A.C. volt-
meters are guaranteed to be correct within 1>^ percent of
full scale at all points; ammeters 2 percent at all points.

These instruments have the following dimensions: Over-all

184 SWITCHING EQUIPMENT FOR POWER CONTROL

height, 12^ inches; over-all width, 15% inches; depth 3 to
3^ inches; mounting screws suitable for switchboards up to 2
inches thick.

Glow Meters. — The electro-static glow meter is a vacuum
tube type of electrostatic potential indicator that may be used
for indication of potential on the line, as a ground detector
connected as shown in Fig. 114 or as an electro-static synchronism
indicator connected as shown in Fig. 115.

FIG. 114. — Glow meter
connected as ground de-
tector.

FIG. 115. — Glow meter connected as syn-
chronoscope.

The indicating device consists of three small bulbs filled with a
rare gas which gives out a vivid orange-red glow on an extremely
small static discharge, such as can be obtained over one section
of a multi-section line insulator. The base of the instrument is
of micarta and the bulbs are mounted between spring clips and
are separated from each other by micarta tubing which forms
barriers for the light from the individual bulbs.

This instrument utilizes the electrostatic discharge of one
section of an insulator column. When used as a ground detec-
tor one bulb is in parallel with the bottom section of each of the
three insulator columns.

Static Synchronizer. — When used for synchronizing, the phase
connections through the top lamps are so made that the lamp will
be out at synchronism. The phases of the two lower lamps are
crossed so that they glow at synchronism. When out of phase
60 degrees, all three lamps have about half voltage impressed on
them and glow with the same brilliancy; when out of phase 120
degrees, one of the bottom lamps is out and the other bottom lamp
and the top one are glowing. If the two circuits are out of
synchronism there will be an apparent rotation of the light in
such a direction as to show whether the incoming line is fast
or slow.

SWITCHBOARD METERS

185

Watt-hour Meters. — The type OA watt-hour meters shown in
Fig. 116 operate on the induction principle. The torque that ro-
tates the disk is proportional to the product of voltage, current
and power factor of the circuit, and is counter balanced by a
retarding force exactly proportional to the speed. The speed of
rotation is, therefore, proportional to the power in the circuit.

Polyphase type OA meters are in reality two single phase meter
elements supported on one mounting frame, both moving ele-
ments being mounted on a common shaft and driving a common
register.

When properly connected, these meters indicate the true power
in a 2-phase 3-wire or 4-wire, or a 3-phase 3-wire circuit, regard-
less of the power factor or the degree of unbalance between
phases.

FIG. 116. — Westinghouse single-phase FIG. 117. — Westinghouse recording
watthour-meter — cover removed. demand watthour-meter.

Extra terminals are provided on the front of the meter under
the cover to facilitate checking the meter while in service. These
terminals are so arranged and connected by test-links that the
test meter can be inserted in the circuit from the front of the
switchboard, for testing the switchboard meter, without opening
the current transformer circuits. By these terminals and links,
the switchboard-meter elements can likewise be disconnected
from the transformer circuits, the current transformers being
short-circuited, and connected to a test load and portable stand-
ard watt-hour meter.

Demand Meter. — The type RA recording demand watt-hour
meter shown in Fig. 117 in one unit measures both the kilowatt
hours consumed and the integrated demand. It indicates on

186 SWITCHING EQUIPMENT FOR POWER CONTROL

a four-counter dial the total kilowatt hours consumed and records
in a permanent form the integrated demand over successive
predetermined time intervals.

It is applicable for determining the demand of power installa-
tions where a permanent record of the demand, involving the
time and length of occurrences, is wanted.

The type RA recording demand watt-hour meter consists of a
watt-hour meter with the usual four-counter register and, in
addition, the mechanism for obtaining a graphic record of the
demand. The time interval of the meter and the advance of the
record paper are controlled by a hand-wound clock mechanism.
Under load, the gear train of the watt-hour meter advances the
counters in the regular manner. At the same time the gear
train causes the ink-carrying pen to advance across the record
paper in proportion to the energy registered. At the end of a
predetermined time interval a stud on the reset wheel releases
the pen gear from mesh with the gear train and a balancing weight
returns the pen to zero where it is again meshed with the gear
train to repeat its advance during the next time interval.

Just before the pen gear is released, the record paper is ad-
vanced a sixteenth inch by the operating spring so that the pen
makes a distinct and readily observed record of the maximum pen
travel, showing both the amount of integrated demand and, by

( the time calibration printed on the

record paper, the time of its oc-
currence.

The reset wheel, which makes one
complete revolution per hour, is ar-
ranged for the insertion of four studs.
When all four studs are used, the
meter has a 15-minute time interval
on the integrated demand. With
two studs in place, arranged 180 de-
grees apart, the meter has a 30-
minute time interval; and with only
one stud, a 60-minute interval.

Graphic Meters. — The type M

Switchboard graphic instruments for alternating and direct-
current circuits shown in Fig. 118 make an accurate and
permanent record of the electrical quantities involved in power
house operation. Records of kilowatt output are especially

FIG. 118. — Westinghoust
graphic recording instruments.

SWITCHBOARD METERS 187

important. The load wave indicated by this instrument fur-
nishes a basis for rates to prospective customers whose probable
demands for electric power during different hours of the day
can be estimated.

Relay Principle. — All instruments operate on the relay princi-
ple, the measuring element actuating only contacts and not mov-
ing the pen directly. In turn, these contacts energize a device
arranged to move the pen. The use of resistances prevents
harmful sparking at the contacts, which are made of special
alloy.

The approximate dimensions of all except direct-current watt-
meters are: over-all width 13^ inches, over-all length 16^ inches,
over-all depth Q/^Q inches.

The record is made by a pen moving in a straight horizontal line
at right angles to the motion of the paper, giving a scale having
rectangular co-ordinates.

The motion of the pen and consequently the sensitiveness of
the instrument may be regulated easily, and the record made
either to show slight variations in the circuit or to slur over these
irregularities and form a more even line. The pen can be made
to travel full scale in any time from 1 to 30 seconds. This motion
is absolutely dead beat so that the pen will not "overshoot."

Paper. — The record paper is supplied in a long roll providing
continuous records for any desired period. It is legibly printed
in black and is inexpensive. The width is approximately 6%
inches, the scale being 5^ inches. Standard rolls are for two
month's service at a speed of 2 inches per hour. The standard
paper speeds are 1, 2, 4, or 8 inches per hour. Each instrument
has a paper collecting roll of 124 feet capacity.

The clock, which turns the paper rolls, is of the electric self-
winding type and operates from the control circuit at the end of
each 2-inch period.

Paper Speed. — If an instrument is desired the speed of which
can be adjusted from 8 to 4 or 2 inches per hour, a clock suitable
for this purpose can be provided with extra sets of gears.

In direct-current ammeters and wattmeters and in power
factor meters, the pen is operated by solenoids energized
through the relay contacts. In alternating current-direct-
current voltmeters, -alternating-current ammeters and watt-
meters, and frequency meters, the pen is operated by a small
motor similarly energized through the relay contacts.

188 SWITCHING EQUIPMENT FOR POWER CONTROL

Ammeters, voltmeters, wattmeters, and frequency meters are
guaranteed correct within 1 percent of full scale at all points.

Meter Elements. — The measuring elements of alternating-
current and direct-current voltmeters, alternating-current am-
meters and alternating-current and direct-current wattmeters
are of the Kelvin-balance type. They are independent of
variations in frequency, external fields, temperature, power
factor, or wave form. Polyphase wattmeters are correct with
any degree of unbalancing of phases. Direct-current ammeters
are of the permanent magnet type with moving coils, and operate
from shunts.

Direct-current wattmeters are similar to the alternating-
current wattmeters except that the series coils are designed to
carry the total current.

Totalizing Graphic. — Type M totalizing graphic wattmeter
is used far measuring the total power in a group of 2 to 12
independent circuits.

It is possible to record on this instrument the total power in
several circuits not in synchronism or of different characteristics
such as frequency, transformer ratio, voltage, etc. These instru-
ments can be made for any capacity and frequency and can be
used with instrument transformers in service, even though
of different ratios. The measuring elements are all mechanically
connected to one set of contacts, so that it is the total pull of all
the elements that closes and opens the contacts. The control
element is supplied for operation by either direct current or by
alternating current, as ordered.

Type U Graphics. — These graphic ammeters and voltmeters
are intended for purposes where graphic instruments that are
easily operated, light in weight, comparatively low in price, and
reasonably accurate are required. The instrument consists of a
solenoid and core acting on an arm that carries the recording
pen, and a continuous strip of paper moved uniformly by a clock
mechanism. To overcome the slight friction of the pen on the
paper, the solenoid is made powerful in its action. Its action
is controlled by a heavy spring, which minimizes inaccuracies due
to slight errors in leveling. The energy consumed by the volt-
meter, including its external resistor, is 25 watts. The energy
consumed by the ammeter is 7 watts, thus adapting it for use
with ordinary current transformer for currents higher than the
current rating of the instrument. On direct current the type

SWITCHBOARD METERS

189

U voltmeters have an accuracy of 2 percent and ammeters 3
percent, with somewhat greater accuracy on alternating current.
Temperature errors, and errors due to ordinary frequency changes
are negligible.

Temperature Indicators. — These devices for switchboard
mounting are desirable, especially in large capacity generators,
in order to know what are the maximum temperatures in the
machine so that the load may be controlled in accordance with
the safe temperature limits of the insulation.

Methods. — Three general methods of temperature measure-
ments may be used: by thermometer, by measuring increase
in the resistance of the windings, and by embedded temperature
detectors. With the first of these, surface temperatures of
stationary parts only can be observed. The second method
gives only average temperatures of the winding and does not
give temperatures of hot spots. It is, therefore, upon the third
named method that the greatest dependence can be placed.

There are two forms of embedded detectors for temperature
measurement: exploring coils, and thermocouples.

Exploring Coils. — Outfits for use with embedded exploring
coils give a direct and continuous indication of temperature. A
separate source of direct & ^ Co//

current of constant voltage
must be provided.

The Wheatstone bridge
principle is used. The
exploring coil is a resistor,
the resistance of which
varies with the temperature
of the mass surrounding it,
and forms the fourth arm
of the bridge. The values of the other three resistances of the
bridge are such that when the temperature of the exploring coil
has reached some predetermined value the bridge is in balance and
there is no difference in voltage between points 2 and 4, Fig. 119.
With the exploring coil at any other temperature, there will be
a difference in voltage indicated on the voltmeter which is
calibrated in degrees. The four arms of the bridge are made
equal at the temperature for which greatest accuracy is desired,
and at this temperature the indications will be independent of
applied control-circuit voltage. The standard temperature

3eries~Re$istor used only
for Voltages above 20.

FIG. 119. — Temperature indicating diagram.

190 SWITCHING EQUIPMENT FOR POWER CONTROL

is 100 degrees Centigrade, but any other temperature may be
chosen for balance. The instrument can be calibrated for any
temperature that the exploring coils can withstand.

The exploring coil is made up of a large number of turns of
copper wire wound on a strip of mica. The finished coil is
about 5 inches long and y± Q inch thick and at normal tempera-
ture has a resistance of approximately 30 ohms.

The bridge resistors are generally mounted in a bridge box
back of the switchboard panel, and any source of direct current
of constant voltage will serve.

Thermocouples. — Outfits for use with embedded thermo-
couples balance the E.M.F. of the test couple against that of
another couple at known temperature; it thus avoids all errors
due to variation in leads, etc., and as it indicates on the "null"
or zero-reading principle, very accurate readings can be obtained.
Danger of short circuit or open circuit when placed in machine
is a minimum.

One thermocouple is embedded in the mass of which the
temperature is to be measured and the other, the "cold" couple,
located where its temperature can be easily recorded on a thermo-
meter. An instrument can then be so connected that it will
show the difference in voltage between the two couples and
therefore the temperature can be easily determined.

Calibrations. — The instrument is calibrated to read directly
the temperature of the test couple that is made by welding copper
and "advance" (nickel-copper) alloy ribbons together. These
ribbons are ordinarily 0.005 inch thick, 0.25 inch wide and of any
desired length. The couple is insulated with mica and micarta
paper to withstand a temperature of at least 150 degrees Centi-
grade. An inherent characteristic of this couple is that its
difference in potential is 42 microvolts per degree Centigrade
difference between the two couples.

The Westinghouse type DT temperature indicator combines
in one case all necessary parts except the test couple. It operates
on the "potentiometer principle." The instrument case con-
tains the "cold" couple which is in contact with the bulb of a
mercury thermometer, by which the temperature of the "cold"
couple is observed.

A dry cell supplies current to a resistance wire equipped with
two sliding contacts. The drop of potential between these con-
tacts is proportional to the current in the wire and to the distance

SWITCHBOARD METERS 191

between them. Two pointers which move with the contacts
indicate the positions of the two contacts. The scale is calib-
rated in millivolts and degrees; divisions on the millivolt scale
are of equal width; divisions on the temperature scale are spaced
according to the E.M.F. law of the couple. A rheostat in the
battery circuit is used for adjusting the current exactly to the
value that will cause a drop of E.M.F. per degree on the tempera-
ture scale equal to the thermo E.M.F. per degree in the couples.
Leads from the thermocouple connect through a sensitive galva-
nometer to the slide wire contacts of corresponding polarity.
If the E.M.F. between the contacts is equal to the thermo
E.M.F., there will be no deflection of the galvanometer. If
higher or lower, there will be a deflection of the galvanometer
in one or the other direction. By changing the distance be-
tween contacts, using the galvanometer as a guide, the posi-
tion at which the slide E.M.F. balances the thermo E.M.F.
is easily located.

In practice, the lower pointer is set at the position on the
scale corresponding with the temperature of the "cold" couple
and the upper pointer is moved until a balance is obtained as
described. Actual temperature of "hot" couple can then be read
directly on the scale.

One galvanometer serves both for measuring the current
in the slide wire, in which case it is connected in multiple with
a shunt, and for indicating balance when it is connected directly
in series with the couple.

Leads. — In ordinary practice, individual copper wire leads are
used to connect each individual couple through a dial switch on
the switchboard to the instrument and a common advance alloy
lead connects all the couples to the instrument. This side of the
circuit is usually grounded in order that no voltage may be
carried to the switchboard by failure of the armature coil insula-
tion to the couple, which would allow generator potential on
the circuit; also in order that any static disturbance may not
affect the accuracy of the instrument.

It is usual to install six thermocouples in each generator.
The leads from these are then brought out to a terminal board
on the generator and from there to the switchboard. By install-
ing a dial switch on the switchboard, connection can be made
readily from the instrument to any one of the couples.

192 SWITCHING EQUIPMENT FOR POWER CONTROL

WESTON INSTRUMENTS

The Weston Electrical Instrument Company makes a very
complete line of instruments for switchboard service as well as
for laboratory and general testing purposes.

Types. — For D.C. service, ammeters and voltmeters are avail-
able in either round cases, illuminated dial fan-shaped cases or
vertical edgewise cases, to suit different conditions. The higher
grade instruments are all made of the pivoted movable coil
permanent magnet type usually known as the "D'Arsonval"

type, with the ammeters
operated from shunts with a
drop of 50 millivolts.

Round Pattern. — The
round pattern meters are
made with binding posts on
the front of the meter or with
rear connected studs or of
the flush type, the latter being
shown in Fig. 120. The am-
meters up to 75 amperes are
self-contained with the shunt
forming an integral part of
the meter. For higher ca-
pacities the shunt is separate.
The current at full scale is

about 0.04 amperes at 0.05 volts so that the energy taken by
the meter is only 0.002 watts. Based on a full load of 1000
amperes the loss in the shunt with 0.05 volts drop is 50 watts
with proportionate losses at other currents. The round pattern
meters, model 57, have an external diameter of 9.562 inches, a
scale length of 6^ inches. A smaller type of round pattern
meter known as the model 24 has an external diameter of 734
inches, a scale length of 5Ke inches and has an accuracy of 1
percent.

Eclipse Meters. — A cheaper line of round meters known as the
"Eclipse" are made on the soft-iron or electromagnetic principle.
The ammeters are connected directly in the circuit and are built
in capacities up to 500 amperes. These meters are made in two
diameters, the same as for the previous types.

Illuminated Dial. — For large D.C. switchboards illuminated
dial meters can be supplied either for attaching by means of

FIG. 120. — Flush mounting round pattern
Weston D.C. meter.

SWITCHBOARD METERS

193

brackets to the front of the switchboard or of the flush type
countersunk in the switchboard. The scale length of these meters
is 11.8 inches and the scale of translucent glass is illuminated
from the rear. The voltmeters can be supplied as differential
meters for paralleling purposes or with zero center where desired.
These meters have a width of 14.62 inches and height of 13.20
inches for the normal type, but a smaller design is available,
91^e inches wide, 8% inches high. For special service instru-
ments are available with a scale length of 28.09 inches, width
27.375 inches, height 19.50 inches, or
with a scale length of 37.65 inches, a
width of 38.75 inches and a height of
29.25 inches.

Edgewise. — Where it is desired to
place instruments in an elevated posi-
tion or very close together, the vertical
edgewise meters shown in Fig. 121 can
be furnished for assembling in carrying
frames accommodating from 2 to 6 me-
ters. These meters are so arranged that
they can be tilted forward at any angle.

A.C. Meters. — A complete line of
A.C. switchboard instruments is also
built by the Weston Company. For
ammeters and voltmeters the soft-iron
or electromagnetic construction is FIG. 121 . — Vertical edgewise

i , i i ,1 j f Weston meter.

adopted and the meters are made of

the round type either 9% inches or 7K inches diameter and

have scales that are fairly uniform.

Wattmeters. — The wattmeters are built on the electrodyna-
mometer principle, as are the synchronoscope and power factor
meter. The fixed winding of a single-phase wattmeter is made up
of two coils which act together to produce the field of the watt-
meter, these being fed from a series transformer. The movable
coil placed inside the fixed coils is connected in series with a
resistor in a voltage circuit. The general appearance of a
single-phase wattmeter is shown in Fig. 122. As the current
in the series (stationary) coils increases the movable (potential)
coil tends to turn so that the fields of the two elements will
coincide. This tendency is resisted by a spring but the movable
coil in turning causes the pointer to pass over the scale until a

194 SWITCHING EQUIPMENT FOR POWER CONTROL

FIG. 122. — Weston indicating wattmeter.

point is reached when the torque of the coils is just equal to the
restraining torque of the spring. The polyphase wattmeter has
two of the single-phase meter elements so located in tandem as to
act on the same shaft.

The field coils of the synchronoscope are very similar to those
of the wattmeter, except that they are wound with much smaller

wire as they are essentially
potential coils in place of
current coils. The field coils
of the power factor meter
are similarly placed but made
in an elongated form.

In all of these instruments
the pointer is made in the
form of a triangular truss
with tubular members, mak-
ing a very stiff construction
with very small weight. An
effective form of air damper
is used, made with very thin
metal stiffened with ribs, the
whole damper being placed in a damper box where the air leakage
is reduced to a minimum, increasing greatly the amount of damping
while keeping down the weight and the moment of inertia.

Synchronoscope. — The Weston synchronoscope has a switch-
board electrodynamometer movement, mounted with the
pointer behind a translucent glass scale and illuminated by a
synchronizing lamp connected to synchronize light. The fixed
coil is connected across the line through a resistor and the mov-
able coil is connected through a condenser across the incoming
machine. The pointer stands normally in the middle of the
scale. The mechanical construction of this instrument is similar
to that of the Weston single-phase wattmeter, except that both
the fixed and movable coils are wound with fine wire.

Since the lamp is dark when the E. M. Fs. are in phase opposition,
and light when they are in phase coincidence and have the same
frequency, the pointer will be seen at rest in the middle of the
scale when perfect synchronism is attained.

When the E.M.Fs. are not exactly in phase or in phase opposi-
tion, there will be torque tending to turn the movable coil, the
value of the torque increasing with the phase displacement.

SWITCHBOARD METERS

195

The direction of the torque depends upon the relative directions
of the currents in the coils; that is, the direction of deflection in-
dicates whether one lags or leads with respect to the other.
If the two machines are not running at the same frequency, the
phase displacement will continuously shift from phase coincidence
through complete cylces of 360 time-degrees, and with it the
torque will vary continuously from zero to plus maximum, back
through zero to minus maximum, etc., thus causing the pointer
to swing back and forth over the scale. Each swing denotes a
shift in phase angle from quadrature plus or minus to quadra-
ture minus or plus, and, therefore, it will coincide with a period of
light or darkness, and the pointer will be seen only during every
other swing; that is, it will appear to rotate in one direction.

FIG. 123. — Diagram of connections. Weston synchronoscope.

The direction of apparent rotation indicates whether the incom-
ing machine is fast or slow and the speed of rotation is a measure
of the amount by which the frequencies differ. If the machines
have the same frequency but are not in phase coincidence, the
pointer will come to rest at some point at one side or the other of
the middle of the scale.

The connections of the various operating parts of the synchro-
noscope are shown schematically in Fig. 123.

Power Factor Meter. — The powerfactor meter is a special
form of electrodynamometer. Its movable system consists of
two circular coils arranged on the same staff and in planes
at right angles to each other. The movable coils of the power
factor meter are practically identical in magnetic strength

196 SWITCHING EQUIPMENT FOR POWER CONTROL

when traversed by the same current, and are accurately and
permanently located in planes at right angles to each other.
The coils are wound by machine and interlaced layer for layer
at diametral crossing points. The completed coil is then treated
with a special cement which gives it exceedingly great rigidity,
and thus assures a permanent relative location of the coils.
The general construction is quite similar to that of the single
phase wattmeter.

On polyphase systems, the movable coils are connected across
leads in which the E.M.F. differs in time-phase, while on single-
phase circuits a phase-splitting device is used. When the current
in one of the movable coils is in time-phase with that in the fixed
coil it will place itself parallel with the fixed coil. If the current
in the fixed coil reaches its maximum at some time intermediate
between the time of maximum current in either of the other coils,
the movable coils will take a position such that the resultant
maximum field, which is in time-phase with the fixed field, due
to the fixed coil will coincide with the fixed field.

Since the fixed field is in time-phase with the load current, and
the field of one of the movable coils is in time-phase with the
E.M.F. between leads, the space position of the resultant field of
the movable coils, which is in phase with the fixed field, will vary
with the phase angle between E.M.F. and current; that is, the
deflection of the movable system is a measure of phase angle or
power factor.

Frequency Meter. — This meter indicates accurately the in-
stantaneous value of the frequency of the system to which it
is connected. Its movement is of the soft-iron type with two
fixed coils, each made up of two sections. They are wound
flat and one is slipped inside the other and at right angles to it.
The movable system consists of a staff carrying a damper, an iron
needle and a pointer; it is mounted in highly polished sapphire
jewel bearings. There are no springs or other connections to the
movable system, therefore, it is perfectly free to rotate.

The shape of the fixed coil is such as to establish with minimum
material a strong field of uniform density, such as is necessary to
the production of uniform scale. The needle is extremely thin
and is made of a special alloy having a low hysteretic constant.

The coils are connected in series across the line, with a reactor
in series with one and a resistor in series with the other. A re-
sistor is connected in parallel with one coil and the reactor, and

SWITCHBOARD METERS 197

a reactor is connected in parallel with the other coil and the re-
sistor; then the whole combination is connected in series with a
reactor, the purpose of which is to damp out the higher harmonics.
The circuits form a Wheatstone bridge, which is balanced at
normal frequency. An increase in frequency will increase the
reactance of the reactors and thus upset the balance of the bridge,
allowing more current through one coil and less through the other.
Therefore, every change in frequency is accompanied by a cor-
responding shifting of the space position of the resultant field,
which is indicated by the pointer.

These A.C. meters are usually made about 9% inches in
diameter but the ammeters and voltmeters can also be furnished
73^ inch diameter.

CHAPTER VII
INSTRUMENT TRANSFORMERS

Functions. — Owing to the small amount of power required for
the operation of A.C. switchboard instruments, circuit-breaker
trip coils and relays, and the difficulty of insulating them for
high voltages or making them with current coils of large capacity,
it is customary to furnish voltage transformers for pressures
over 600 volts and to use current transformers where the current
exceeds a certain value or the voltage is above 2400 volts. For
the purpose of interchangeability most instruments and relays
used with transformers are made with voltage coils to be operated
at a maximum of 150 volts and current coils for a maximum of 5
amperes.

Voltage. — The voltage transformers are made of the dry type
for pressures of 200 to 6000 volts, while oil insulated voltage
transformers are made for pressures of 200 to 60,000 volts or
higher. Where these voltage transformers are used with from
one to three instruments they are usually compensated to give
accurate transformation ratios at an output of 15 volt amperes,
while with a greater number of instruments or when used with a
regulator or similar device they are compensated to give a correct
ratio at 100 or 200-volt ampere outputs.

Currents. — Current transformers are made in various designs,
either dry or oil immersed, depending on the voltage. As a
rule the current transformer steps down from a comparatively
large current to a smaller one and the primary consists of a few
turns connected directly in the main circuit. For very accurate
work the number of ampere-turns should be at least 600 but
where great accuracy is not required and the secondary load is
small the number of primary ampere-turns can be greatly reduced.
For currents of 600 amperes or more, transformers with accurate
current ratio and very small "phase displacement error" can
be made without any primary winding and arranged to slip over
the cable, switch stud, bus bar strap or similar connection, which
then forms the primary. For use with relays or with ammeters

198

INSTRUMENT TRANSFORMERS 199

calibrated specially current transformers of this type can be
made for ratios down to 100-5, or even smaller in certain cases.

Oil Immersed. — For high voltage service oil immersed current
transformers are used and where it is desirable to have two differ-
ent current ratios for the operation of various instruments and
relays it is possible to build transformers with one primary coil,
two iron circuits and two secondary coils to give the two different
ratios desired. Dry type transformers are also built of this
"double secondary" construction.

By the use of current and potential transformers low voltage
circuits are obtained with characteristics in practical agreement
with the high voltage circuit. Current transformers are ex-
tensively used to obviate the necessity of carrying large or high
voltage conductors to instruments and protective devices.

Purpose. — An instrument transformer is a device suitable for
use with measuring instruments in which the conditions of cur-
rent, potential and phase in the primary or high voltage circuit
are represented with acceptable accuracy in the secondary or low
voltage circuit.

While accuracy is of vital importance, it is absolutely essential
in current transformers that their construction be such as to
withstand momentarily short-circuit currents many times their
rated carrying capacity without injury. Furthermore, it is of
great importance that the design afford a high degree of insula-
tion. Unusual care has been exercised in the design of trans-
formers to provide a high factor of safety.

Load. — Tripping coils of most protective devices usually
impose a heavy "burden" upon current transformers. Where
extreme accuracy is required, it is recommended that separate
instrument transformers be used to supply energy to instruments
or meters, and that tripping transformers be used in connection
with trip coils of protective devices.

Precautions. — Current transformers should not be mounted
where they will be exposed to unduly high temperatures, oil
drippings, moisture, etc., and care should be taken that the
primary terminals are properly insulated.

In mounting current and potential transformers, sufficient
distance should be provided between terminals of adjacent trans-
formers and between terminal and ground, to prevent flash-over
due to momentary voltage surges. The transformer frame and
secondary windings should be thoroughly grounded to eliminate

200 SWITCHING EQUIPMENT FOR POWER CONTROL

electrostatic charges and afford protection to attendants. Con-
tact to ground should be thoroughly inspected before working on
the circuit.

The secondary circuit of current transformers should not be
opened with current in the primary, owing to the high voltage
momentarily induced when the circuit is opened. It is well al-
ways to short-circuit the secondary windings of current trans-
formers before disconnecting instruments, meters, or tripping
coils.

Transformers should be handled with care to prevent mechani-
cal injury or possible weakning of insulation.

Makers. — Nearly all manufacturers of instruments and oil
circuit breakers make current and potential transformers for use
with them. Those of the Condit Company and the Westinghouse
Company have been selected for description as being fairly typical.

Types. — The current transformers of the Condit Electric
Manufacturing Company, are built in two sets of types, the
*B' for circuit-breaker tripping, and the 'S' intended for use
with meters as well as trip coils.

FIG. 124. — Condit Electric & Mfg. Co. current transformer type B-6.

Type B-6. — This type shown in Fig. 124 is intended for primary
windings from 5 to 200 amperes at voltages not exceeding 7500
for either 25 cycles or 60, to carry a load of one ammeter and one
indicating wattmeter for the best efficiency and a maximum load
of one ammeter and one circuit-breaker coil. It has a capacity
of about 50 volt amperes. It is made with a wound primary con-
taining the proper number of turns, and it is designed to stand the

INSTRUMENT TRANSFORMERS

201

electromagnetic and thermal effects resulting from sustained
short circuits.

Type B-4.— The type B-4, Fig. 125, for currents from 300
to 600 amperes at voltages not exceeding 7500, is intended for
slipping over a cable or stud and is provided with a circular open-
ing 2 inches in diameter. It has an output of 40 volt amperes
with 5 amperes in the secondary at 60 cycles and 20 at 25 cycles.

Fio. 125. — Condit Elec. & Mfg. Co. current transformer type "B-4."

Type B-5. — This is made for currents from 600 to 1200 at
voltages not exceeding 4500 and is intended for slipping over rec-
tangular bars and has an opening of 1% Q x 4^f 6 inches. It
has same output as the type B-4 and same general appearance
except provided with a rectangular opening in place of circular.

Type B-8. — This is built for currents from 1500 to 3000 and is
intended for slipping over rectangular bus bars or multiple cables
for voltages not exceeding 4500. It has an output of 50 volt
amperes at 60 cycles and 25 at 25 cycles. It has an opening
2% x 4^ inches.

These larger capacity transformers are designed primarily
for operating circuit-breaker trip coils, but they may be used to
operate indicating meters in conjunction with trip coils and will
afford the usual accuracy required of indicating meters for switch-
board service.

Type B-7. — These current transformers are built for currents
from 300 to 500 amperes for voltages up to 15,000 and are intend-
ed to withstand heavy short-circuit stresses without distortion.
It has the same output as the B-4. The B-9 and B-ll trans-
formers have current ratings from 5 to 300 amperes for voltages
up to 25,000 and 50,000 volts respectively for indoor service and
the B-13 and B-14 are the corresponding outdoor transformers.

202 SWITCHING EQUIPMENT FOR POWER CONTROL

Type SI & SC. — The type SI current transformers are built
double ratio for currents from 5 to 800 amperes and voltages up to
15,000 for circuit-breaker trip coils and indicating meters. It can
readily be used as a differential transformer, and is built to with-
stand short-circuit stresses on large systems. It has an output
of 60 volt amperes at 60 cycles and 30 at 25 cycles. The type
SC is designed primarily for use with instruments where a high
degree of accuracy is desired. It resembles the type SI in its
general features.

FIG. 126. — Condit Electric Mfg. Co., potential transformer, type "W.'

Voltage Transformer. — The type W transformer, Fig. 126, is dry
insulated, thoroughly impregnated, and exceptional care has been
exercised to provide a high factor of insulation. All transformers
have one primary and one secondary lead properly marked to
indicate the polarity. The windings are so related that the in-
stantaneous "ingoing current" of the marked high voltage or
primary lead corresponds to the "outgoing current" of the
marked low voltage or secondary lead. The transformer is so
constructed that a minimum space is required for its instal-
lation. For pressures of 2500 volts or less, the cut-out base may
be furnished as an integral part of the transformer and makes a
very compact and neat arrangement. On pressures in excess of
2500 volts the fuse base must be separately mounted. Oil
insulated transformers are supplied for pressures in excess of
5500 volts.

GENERAL ELECTRIC TRANSFORMERS

The General Electric Company have a very complete line of
current and potential transformers for all classes of service prac-

INSTRUMENT TRANSFORMERS

203

tically paralleling the line of Westinghouse transformers whose
description follows.

WESTINGHOUSE TRANSFORMERS

Type K. — Westinghouse current transformers, type A (dry
type) indoor, are designed for normal voltage of 4600 2-
wire, 1150 3-wire, test voltage for one minute of 14,000 2-wire,
5000 3-wire; for 25 to 133 cycle circuits; capacity 25 volt amperes,
compensated for 12^ volt amperes.

Two-wire. — The type K 2-wire transformers comprise a line
of low priced transformers of good accuracy, available over a large
range of application. This type is suitable for ammeter, watt-
meter, or watt-hour meter use, but may be used also for operating
relays and circuit-breaker trip coils where the load at 4 amperes
does not exceed 25 volt amperes at 25 cycles or 65 volt amperes
at 60 cycles. They should not be used with relays where the
circuit-breaker trip coil is connected in series with the relay.

Three-wire Type K. — Designed for use with watt-hour meters
on 3-wire distribution systems. The primary consists of two
separate windings, one of which is connected in each outside wire
of the 3-wire system, and the secondary winding is connected
to the watt-hour meter. When so connected, the watt-hour
meter measures the total output of the system. The ampere
rating refers to the current in the outside wires.

FIG. 127. — Westinghouse current transformer type " KA."

Types KA and KB. — These dry type indoor transformers are
built for a normal voltage of 6900 and 13,800, a test voltage
of 16,500 and 33,000 for 1 minute; for 25 to 133 cycle circuits;
capacity 50 volt amperes, compensated for 25 volt amperes. A

204 SWITCHING EQUIPMENT FOR POWER CONTROL

Hand Hole
Cover

high degree of accuracy in the ratio of primary to secondary
current and a minimum phase displacement error are obtained
in these transformers. This type is for indoor use in all cases
where highest accuracy is required.

As shown in Fig. 127, the transformers are arranged with the
primary leads on the opposite ends of the coils, an arrangement
well adapted for switchboard use. Lugs are provided for
mounting purposes.

Type KC. — These dry type indoor transformers are built
for a normal voltage of 23,000, test voltage of 52,200 for 1
minute; for 25 to 133 cycle circuits; capacity 50 volt amperes,
compensated for 25 volt amperes. They are mounted in cast-
iron end caps which are
filled with insulating com-
pound. This construction
insures ample insulation
between the high voltage
winding and the secondary
winding or the core.

Double secondary type
KC transformers shown in
Fig. 128 are similar in con-
struction and voltage
rating to the type KC,
but have two independent
secondary windings, each
compensated for 25 volt
amperes. One of these

transformers, therefore, takes the place of two ordinary trans-
formers on the same circuit.

Relay Transformers. — Type KR (dry type) indoor trans-
formers for operating relays and circuit-breaker trip coils have a
maximum voltage of 6900, test voltage, 16,500 for 1 minute,
for 25 to 133 cycle circuits. This line of transformers in capa-
cities 5 to 200 amperes inclusive is supplementary, for circuit-
breaker use, to the through type FR transformers listed in
capacities up to 500 amperes. These transformers have sufficient
capacity to operate relays or trip coils and will have an error in
ratio not exceeding about 10 per cent, where the load at 4 amperes
does not exceed 25 volt amperes at 25 cycles or 65 volt amperes at

FIG. 128. — Westinghouse current transformer
type " KC " double secondary.

INSTRUMENT TRANSFORMERS 205

60 cycles. They should not be used with relays where the circuit-
breaker trip coil is in series with the relay.

These transformers are for use only with relays, or circuit-
breaker trip coils. They have sufficient capacity for operating
circuit breakers within the limits of ordinary accuracy demanded
in such service but should not be used for connection to measuring
instruments. The general type of construction is similar to
type KA transformers, except that these are much smaller.

The through-type FR (dry type) indoor transformers for
operating relays and circuit-breaker trip coils, for 25 to 133
cycle circuits are similar to types FS and FB ; but in the capaci-
ties covered by this line, 100 to 500 amperes inclusive, a through-
type transformer cannot be made of sufficient accuracy for
ordinary use in connection with measuring instruments. This
line of transformers is, therefore, primarily adapted for circuit-
breaker tripping, either through relays or by direct connection
to the breaker.

Special Calibration. — In order to obtain the advantage of a
through-type transformer of low current rating for instrument
service, these transformers may be so used where it is possible to
calibrate the instrument with the transformer. This application
can only be made in the case of ammeters, and requires the use of
a calibration curve for each instrument. The same transformers
should not, however, be used both for instrument work and
circuit-breaker work. These transformers have sufficient capa-
city to operate relays or trip coils and will have an error in ratio
not exceeding about 10 per cent, where the load at 4 amperes
does not exceed exceed 25 volt amperes at 25 cycles or 55 volt
amperes at 60 cycles. They should not be used with relays
where the circuit-breaker trip coil is in series with the relay.

Through-types. — Types FS and FB (dry type) indoor trans-
formers have a rated voltage of 2300, test voltage 10,000 for
1 minute, for 25 to 133-cycle circuits. These transformers in
capacities up to 6000 amperes have a potential rating of 2300
volts. By the use of longer insulating tubes over the primary
conductor, they may be used at higher voltages. In sizes up to
and including 1000 amperes, they have a capacity of 25 volt
amperes and are compensated for 12^ volt amperes; above 1000
amperes they have a capacity of 50 volt amperes and are
compensated for 25 volt amperes. These "through-type"
transformers have no primary windings but slip over a cable,

206 SWITCHING EQUIPMENT FOR POWER CONTROL

stud, or bus bar, which forms the primary of the transformer.
The type FS is intended for cables and round studs, and the type
FB for rectangular bus bars.

Short Circuits. — The momentary current due to a heavy short
circuit on a large system is extremely great, and the mechanical
stresses set up between the primary and secondary windings of a
current transformer due to this current are extraordinarily large.
The "through-type" of transformer is the only type in which
these stresses are balanced up within the transformer itself;
and they are therefore of special value where, due to special
conditions, other types of transformers are liable to overstrain
from such stresses.

Outdoor Types.— Types MA, MB or MC (dry type) outdoor
transformers have rated voltage of 6900, 138,000 and 23,000;
test voltage of 16,500, 33,000 or 52,200 for
1 minute; for 25 to 133 cycle circuits; capacity
50 volt amperes, compensated for 25 volt
amperes. These transformers are mounted
in cast-iron end caps with the leads extending
downwards through suitable bushings. The
transformers are impregnated with an in-
sulating compound which thoroughly seals up
joints between the laminations and end caps.
Oil Insulated.— Types OA, OB or OC (oil
insulated) transformers have a normal
voltage of 34,500, 44,000 or 66,000 and a test
voltage of 69,000, 88,000 or 132,000 for 1
minute; for 25 to 133 cycle circuits; capacity
50 volt amperes, compensated for 25 volt
amperes. These transformers are designed
for separate mounting, in compartments or
otherwise. They are heavily insulated between
primary and secondary windings and form a
barrier of great strength between the line and
the instrument circuits.

Double Secondary. — In cases where it is
desirable to operate relays or circuit breakers
together with indicating instruments or watt-hour meters, trans-
formers having two independent secondary circuits can be fur-
nished. The instruments can then be isolated from the relays or
circuit breakers, and the accuracy of the former will be unaffected
by the heavy load represented by the latter.

FIG. 129.— West-
inghouse outdoor oil
immersed current
transformer 66 K.V.

INSTRUMENT TRANSFORMERS

207

Outdoor transformers like Fig. 129 differ from the indoor type
only in having high voltage outlet bushings suitable for outdoor
service.

Voltage Transformers. — These are made either dry type or
oil insulated. The dry type voltage transformers are mounted in
end frames and are adapted for use on voltages up to 6000. The
end frames of transformers up to and including 2000 volts have
lugs cast on them for mounting fuse blocks.

Oil Insulated Voltage Transformers. — The oil insulated type
voltage transformers are designed for use on voltages from 2300
to 66,000. Up to 6900 volts they are
mounted in cases made to fit in cells
or in the limited space behind switch-
boards. For voltages up to 6900, they
are mounted in cast-iron cases provided
with mounting lugs. For voltages
above 6900, the transformers are built
for floor mounting. For voltages of
4000 to 6900 inclusive, the trans-
formers are so designed that the high
voltage leads can be brought through
either the top or the sides of the case,
by means of the extra bushing holes
and flanges. This feature is of par-
ticular advantage in switchboard
wiring. Oil insulated transformers for
outdoor operation like Fig. 130 can be
furnished for standard voltages.

The ratio of transformation should be such as to give a nominal
voltage of 100 on the instruments. Thus, for a 2200-volt cir-
cuit, a 2000-100 ratio should be used, making the normal voltage
on the instruments 110.

For protection against line surges, transformers designed for
voltages of 22,000 and above, have choke coils mounted in their
cases and connected between the transformer windings and the
line.

Outdoor Metering. — These equipments as shown in Fig. 131
are designed for supplying service from high voltage transmission
lines where the expense of a substation is not warranted, these
metering equipments being furnished enclosed in weatherproof
casings. Each equipment consists of a standard polyphase

FIG. 130. — Westinghouse
outdoor oil immersed poten-
tial transformer 66 KV.

208 SWITCHING EQUIPMENT FOR POWER CONTROL

watt-hour meter, two current transformers, a polyphase voltage
transformer, and three choke coils to protect the transformer
windings against high-frequency disturbances; all enclosed in a
sheet steel case with cast-iron cover. The sheet steel case is
subdivided into 2 compartments, one of which is filled with oil
in which the transformers and choke coils are immersed, while

FIG. 131. — Westinghouse outdoor metering equipment.

the other serves to enclose the meter and meter panel. On the
meter panel are also mounted two fuses to protect the voltage
circuit of the meter and two calibrating links located in the cur-
rent circuit of the meter. The meter may be read or checked
upon opening the hinged door which covers the entire front of
the meter compartment. The arrangement is such that the
entire outfit, including meter panel, can be raised out of the tank
without disconnecting the meter leads.

CHAPTER VIII
LIGHTNING ARRESTERS

The apparatus furnished for the protection of electrical
equipment against the effects of lightning or static disturbances
of any kind is usually considered as part of the switching devices
and is frequently included in the same contract as the switch-
board and the switching apparatus. For this reason it seems
logical to take up its consideration in this book after the circuit
breakers, relays, meters and instrument transformers.

Terms. — Lightning, from the protective standpoint, is a
term used to cover all kinds of disturbances in electrical trans-
mission systems that take the form of high voltage. There
are two kinds of lightning, viz.: that due to atmospheric lightning,
and that due to internal disturbances in the line itself. Lightning
arresters are designed to take care of atmospheric lightning
and those internal surges that are transient in nature, but not
those that are continuous.

Cause. — Atmospheric lightning is due to discharges that
occur between two oppositely charged clouds or between a
cloud and the earth.

Direct Strokes. — When a discharge from a cloud strikes an
electrical conductor directly, it almost always breaks down
the insulation at or very near that point. It rarely travels
along a transmission line far enough to reach an arrester and if
it did it would probably destroy any type of arrester except
possibly an electrolytic one. Arresters are not designed, there-
fore, to handle direct lightning strokes. It is usually the line
insulators rather than the station apparatus that are injured by
these direct strokes and they are best protected by overhead
ground wires well and frequently grounded rather than by
arresters.

Induced Strokes. — By far the greater number of disturbances
in transmission systems due to atmospheric lightning are induced
therein by discharges between clouds overhead or between a
cloud and the earth in the vicinity.
14 209

210 SWITCHING EQUIPMENT FOR POWER CONTROL

Surges. — Internal surges are caused by any change in the
load conditions. They may be either transient or continuous.
Transient surges are caused by sudden changes of loads such as
are occasioned by switching, the operation of circuit breakers,
etc. They are usually comparatively unimportant but may be
quite severe where a very heavy current is broken suddenly.
Continuous surges are caused by arcing grounds which result in
occillations of great power at a frequency usually a few thousand
cycles per second. This frequency is inherent in the line and
is determined by the capacity, resistance, and inductance of the
line. Surges are very destructive and frequently result from
breakdowns of insulation caused by induced lightning. Light-
ning arresters (except the electrolytic for a limited time) cannot
handle continuous discharges such as these without being
destroyed by overheating. Arresters do protect against arcing
grounds, however, by protecting against the induced surges
that are their primary cause in so many cases.

Displaced Neutral. — On a transmission line another cause of
trouble that results in a continuous high voltage is a displaced
neutral due to a ground on one phase of an ungrounded neutral
system. This raises the voltage of the other phases above
ground abnormally. In the case of transformers of high ratio
this effect may appear even on the opposite side of the trans-
former and cause arresters to discharge continuously and be
destroyed without apparent cause, inasmuch as the ground may
exist a great distance away and on a different circuit.

The arresters described in this book are designed to take
care of atmospheric lightning and transient internal surges
but not of continuous surges.

Importance of Good Ground. — Too much importance cannot
be attached to the making of proper ground connections. These
should be as short and straight as possible. A poor contact
will render ineffective every effort made with choke coils and
lightning arresters to divert the static electricity into the earth.
It is important, therefore, not only to construct a good ground,
but in doing so to appreciate thoroughly the necessity of avoiding
unfavorable natural conditions. Many lightning arrester troubles
are traceable directly to poor ground connections.

Connection to Existing Grounds. — Direct connection to an
underground pipe system (such as a city water main), furnishes
an excellent ground, because of the great surface of pipe in

LIGHTNING ARRESTERS

211

contact with the moist earth and the maximum number of
alternative paths for the discharge. A supplementary ground
line should always be connected to the structural steel framework
of the station, and to any nearby trolley rails. In water power
plants the ground should always include a connection to the
pipe line or penstock and to the case or frame of the apparatus
to be protected.

Ground Conductor. — For the conductor between the arrester
and the ground connection, either strap copper or copper tubing
should be used. It is important that a conductor having the
greatest possible superficial area be used, inasmuch as high
frequency discharges are carried almost wholly on the surface of
the conductor. Strap copper, having a section say ^2 inch by
1^ inches, makes a good conductor for the average conditions.
Such a ground conductor may be fastened directly to the station
structure with wood screws The course of the ground conductor
should be direct and have few turns — the fewer the better.

D.C. Arresters. — For direct-current service, lightning arresters
are required for comparatively low voltages, but of high discharge
capacity. The most satisfactory arresters, in order to ade-
quately protect motors, generators and converters, must have the
ability to discharge static at the lowest possible voltage rise
above normal operating voltage, without danger of the generator
current following and destroying the arrester. In general
direct-current arresters are of two kinds: first, those which
allow the generator current to fol-
low a discharge when normal volt-
age is established and then disrupt L^
it; and, second, those in which
the generator current does not
follow a static discharge. The
latter type requires no resistance
in the static discharge path, as in
the case of the first type, to limit
the generator current, and pro-
vides the greatest freedom for dis-
charge of static and the lowest
voltage discharge point.

Multipath Arrester. — For A.C. or D.C. service for voltages not
exceeding 1000 a "multipath" arrester, Fig. 132, has been
developed by the use of a carborundum block fastened between

FIG.

132. — Multipath lightning
arrester.

212 SWITCHING EQUIPMENT FOR POWER CONTROL

the two terminal plates and allowing the static discharge to spread
itself over a number of minute discharge paths. The normal
voltage between the line and the ground is divided into so many
minute gaps that the voltage across each gap is too small to
maintain an arc after the discharge has passed.

Condenser Arrester. — One form of condenser arrester consists
of a condenser alone; the other consists of a condenser in series
with a spark gap, the condenser being shunted by a high re-
sistance. The condenser is of the flat plate unit-form, which,
in case of burnout, is easily exchanged without the necessity
of dismounting the arrester. The condensers have a capacitance
of one microfarad, which is equivalent in capacity to 100 miles of
average line.

In the arrester without gap the condenser is connected directly
across from line to ground, whether mounted on pole or car.
Direct current cannot pass through a condenser, and there is,
therefore, no leakage. The condenser is charged to normal
voltage, but as soon as static surges appear the condenser dis-
charges these surges at any voltage above normal. The use of the
arrester without gap is important in the protection of apparatus
having weakened insulation. Many railway cars are operating
with motors that will not stand a breakdown test at the voltage
necessary to bridge an arrester gap, but with this type of arrester
they are given protection.

In the arrester with gap the principal differences are that the
condenser is always discharged and, therefore, affords a slightly
increased capacity for discharge of any static wave of great
volume. The use of the gap also provides a means for testing the
operation of the arrester by the use of tell tale papers and pro-
vides an easy way to make and break the circuit for testing the
condenser.

Non-arcing Type. — One of the first successful high voltage
arresters for A.C. service was based on the discovery of "non-
arcing metal " by Mr. A. J. Wurts. The peculiar property of this
metal is that an alternating current will not maintain an arc
between adjacent cylinders of this metal, provided the voltage is
not too high, and that the power current that followed the
lightning discharge does not vaporize too much of the metal. The
first condition was met by having a fairly large number of very
small gaps in series, and the second condition gave no trouble on
the early high voltage installations where the amount of power

LIGHTNING ARRESTERS

213

Mounting Iron not extend
under base more than if

current was comparatively small. For large amounts of power it
was necessary to use resistances in series with the spark gaps to
limit the current and these resistances reduced the effectiveness
of the arresters. For very high voltages different schemes were
used to reduce the number of gaps required and it was found that
by shunting a certain number of these gaps the effectiveness of the
arrester was increased.

Fig. 133 shows an arrester of this design intended for service
on 6600-volt lines where the capacity does not exceed 2000
K.V.A. The non-arcing cyl-
inders are contained between
porcelain insulators in such a
way that the seven cylinders in
each of the two sets have air
gaps of about ^2 inch between
adjacent cylinders. The marble
slab forming the base of the
arrester also has mounted on it
two graphite resistance rods
shunting some of the gaps.
Modifications of this scheme
were used for the "low equiva-
lent/' "multigap," "multiphase"
and similar "shunted gap" ar-
resters that were installed before
the electrolytic arresters were

brought out and which are still giving good satisfaction in many
plants operating at voltages as high as 88,000.

Multi-chamber Type. — The arresters previously described are
a few of the many types made by the Westinghouse Electric &
Manufacturing Company for moderate voltage circuits, and the
General Electric Company have a somewhat similar line of
arresters. For use on A.C.. systems up to 3000 volts Schweit-
zer & Conrad Inc. build the multi-chamber arrester which
consists of a number of discharge gaps connected in series with a
resistance and mounted in a porcelain housing. This housing is a
porcelain tube closed at both ends, except for a venting hole at the
lower end. The mounting bracket is an integral part of the main
housing and is adapted for either cross arm or wall mounting.

Operation. — The operating element of the arrester consists
of five series gaps, each gap being mounted in a separate cylin-

FIG. 133. — Non-arcing arrester.

214 SWITCHING EQUIPMENT FOR POWER CONTROL

drical chamber in a block of insulating material. These cylin-
drical chambers are open only at one end, and the discharge gap
in each chamber is located near the closed end.

When a discharge passes through this arrester, the heated air
back of each gap in the closed end of the respective chambers
blows the arc out towards the open end of the chamber. This
blowout action is very effective in extinguishing the arc and in
rupturing the dynamic current which tends to follow the high
voltage discharge.

FIG. 134. — Schweitzer & Conrad multi-chamber arrester.

As will be seen from Fig. 134, the insulating blocks are as-
sembled so that the openings of adjacent chambers are diametri-
cally opposite in the porcelain tube, making the path between
adjacent gaps a maximum. This arrangement prevents bridging
of the gaps by the arc or the arc vapor. The spark gap points
are made of a non-arcing metal, which feature assists in extin-
guishing the arc.

Electrolytic Type. — While arresters of various types have been
developed and are in service for high voltage installations, the
electrolytic arrester has been found to furnish the maximum

LIGHTNING ARRESTERS

215

amount of protection and is the one most frequently employed
by the Westinghouse Electric & Manufacturing Company and
the General Electric Company, where continuity of service and
value of the equipment to be protected makes it advisable to
furnish the highest grade of equipment.

of electrolytic lightning arrester.

Arrangement. — The essential parts of an electrolytic lightning
arrester of Westinghouse design are shown in Fig. 135. The ar-
rester consists of a system of aluminum cup shaped trays (sup-
ported on a porcelain and secured in frames of treated wood)
arranged in a steel tank. The system of trays is electrically

216 SWITCHING EQUIPMENT FOR POWER CONTROL

connected between line and ground, and between line and line.
These trays contain a liquid electrolyte which on charging the
arrester forms a film on their surfaces. This film prevents
flow of current at normal voltages, but forms a free path for
abnormal voltages or static discharges. Upon cessation of the
abnormal stress the film regains its original resistance practi-
cally instantaneously, and prevents power current from following
the discharge.

These aluminum trays are separated from each other by por-
celain spacers arranged around the edge of the tray insuring
positive separation and ample space for the escape of such gases as
are formed during a heavy discharge. The porcelain spacers
vary slightly in thickness, but this does not affect the operation
of the arrester because the resistance of the cell resides primarily

on the film of the tray and
only slightly in the electro-
lyte. The trays are thoroughly
treated chemically and elec-
trically and are shipped out
with the film already built up.
The General Electric ar-
resters have the same main
features but the details of
construction are somewhat
different.

132 K.V. Arrester. — Fig.
136 shows the arrangement
of tank bushings, trays and
supports used for electrolytic
arresters for 132 K.V. service.
As may be noted the tank is
elliptical in shape with two
terminals, the longer one con-
necting to the line circuit,
the shorter one being used
for the neutral connection.

These tanks are thoroughly grounded and the aluminum trays
are mounted on insulated supports and provided with barriers
to obviate the likelihood of any high voltage jumping from the
trays through the oil to the grounded tanks.

Gaps. — For high voltage service, horns with sphere gaps are

FIG. 136. — Westinghouse electrolytic
lightning arrester 132 K.V. Assembly
of complete pole and tray column.

LIGHTNING ARRESTERS

217

provided and charge and discharge resistors furnished, these being
connected in series with the aluminum trays and under normal
conditions there is no voltage impressed on the trays. Abnormal
voltage or high frequency surges will bridge the gaps allowing
current to pass into the trays.

The horn-type gap was first used and is still employed in many
cases. It is so arranged that any arc forming will follow the
natural tendency to rise and will be extinguished by the magnetic
blowout effect and the increased width of spacing at the top of
the horn.

Sphere Gaps. — A sphere gap has a shorter dielectric spark lag
than the horn gap, i.e., it has a greater speed of discharge. 'The
use of sphere gaps on high voltage arresters considerably in-
creases the protection afforded the apparatus. On the lower
voltage arresters the rods forming the horn gaps are of such a
diameter that they have practically the same effect as sphere
gaps; i.e., the gap is so small in proportion to the diameter of the
horn that the effect is the same as if sphere gaps were used.
Where sphere gaps are employed, they have horn extensions rising
above the spheres to assist the arc to rise and thus be quickly
extinguished.

FIG. 137.— Westinghouse impulse gap for arrester.

Impulse Gap. — The latest development along the line of high
speed gaps used by the Westinghouse Company is the impulse
gap shown diagrammatically in Fig. 137. This impulse gap is

218 SWITCHING EQUIPMENT FOR POWER CONTROL

stated to excel every other known gap in assisting arresters to
give protection from lightning and other high frequency or high
voltage disturbance. The original horn gap has considerable
time lag, allowing high frequency surge before discharging and
giving protection. The sphere gap partly prevents this situation
by eliminating the time lag so that all frequencies are discharged
at the same voltage. The impulse gap has a negative time lag,
i.e., the higher the frequency the lower the voltage at which the
gap discharges. Thus the impulse gap automatically selects
the dangerous surges and gives protection more quickly than any
other known form of gap. With the impulse gap the high fre-
quency discharge voltage may be as low as two-thirds or even one-
third of the normal frequency value. It is therefore possible to
use a gap setting that will permit of the desired degree of pro-
tection against dangerous surges and not permitting too frequent
discharging on minor surges at normal frequency.

Gap Speed. — The high speed of the sphere gap as compared
with the horn gap is due to the elimination of the time required
to build up a sphere of equi-potential surface on the discharge
part of the horn gap. The sphere of the sphere gap provides at
once for this, and practically eliminates corona. It does not,
however, give the desired protection against the steep-wave
front or high frequency surges due to its in-
ability to discharge these disturbances at
lower voltages than the normal frequency
setting of the gaps.

In the impulse gaps, however, the advan-
tage of high normal frequency setting of the
^ps can be had without the corresponding
disadvantage of reduced protection, since
the high frequency breakdown value of the impulse gaps is
much lower.

The schematic diagram of the impulse gaps is shown in Fig.
138. This impulse gap uses a circuit that at normal frequency is
balanced as to voltage, but becomes unbalanced and starts a
discharge in case of any high frequency surges. At normal
frequency there is no difference of potential between the mid-
point of the condenser and the auxiliary electrode midway be-
tween the auxiliary horn and sphere gaps. A high frequency,
however, passes freely through the condensers and piles up its full
voltage across the resistance and carries across one-half of the

LIGHTNING ARRESTERS

219

total gap. This gap, therefore, breaks down, resulting in the
total voltage being impressed on the remaining gap which breaks
down in turn. Breakdown at each half of the gap is facilitated
by the fact that the auxiliary electrode is small in size, having
needle gap characteristics so that the discharge voltage at each
half of the gap is about Y± rather than Y^ of the total gap
between the spheres.

Oxide Film. — Owing to the use of the liquid electrolyte, the
necessity for periodical charging and the comparatively high
price of the aluminum cell electrolytic arrester, the oxide film
arrester has been developed by the General Electric Company
who have had some in service, experimentally, for some time
and have lately placed them on the general market. This oxide
film arrester depends for its functioning on the fact that certain
dry chemical compounds, such as lead peroxide, can be changed
rapidly from a very good conductor to an almost perfect non-
conductor, litharge, by the application of a slight degree of heat,
such as would be caused by the passage of a lightning discharge.

FIG. 139. — Cylindrical choke coil.

Choke Coils. — Whenever a surge of high frequency or steep-
wave front due to lightning or any other cause travels along a
line and strikes an inductive winding, it builds up a high voltage
to ground. Choke coils are frequently furnished for use on line
circuits to take the brunt of such surges and to provide a point
where the lightning arresters can be connected in to secure the
maximum protective effect. Besides relieving the end turns of
the power apparatus from the first shock of the surge and flatten-
ing it out before it can enter the power apparatus, it delays the
progress of the surge and the piling up of the voltage moment-

220 SWITCHING EQUIPMENT FOR POWER CONTROL

arily at the line, thus giving the arrester more time and more
tendency to discharge and relieve the line.

While a very small choke coil has low protective power, very
large coils will introduce excessive reactance in the line and impair
the regulation. It is, necessary therefore, to choose for any
service a choke coil proportioned to the needs of the apparatus.

Cylindrical Coil. — Fig. 139 shows a choke coil suitable for
50 K.V. operation. The coil consists of 20 turns of aluminum
rod formed into a cylinder 15 inches in diameter, and provided
with bracing clamps to rigidly separate the turns and to give
mechanical strength to the helix. Similar coils 9 inches in diame-
ter can be supplied having a fewer number of turns and approxi-
mately one-sixth the impedance.

Horn Arresters. — For plants of moderate capacity for outdoor
high voltage service, particularly where the lightning conditions
are not very severe, the cost of electrolytic lightning arresters
may not be justified by the value of the equipment which they
are protecting. For such cases, horn type lightning arresters
can be utilized to advantage.

Railway Industrial & Engineering Type. — Such arresters made
by the Railway & Industrial Engineering Company are usually
combined with triangular shaped choke coils as shown in Fig. 140.
With this arrangement, one side of the choke coil acts as one
of the horns of the arrester. The coil is used in this way, first as
a magnetic blowout to hasten the travel of the arc up the horns,
and second to increase the speed of operation of the arrester.
The incoming line is connected to the outside turn, and the path
of the power circuit is around the coil and out through the center,
so that the surge entering the coil meets its first obstruction at
the first sharp upward turn of the coil opposite which is mounted
the ground horn. The voltage will build up at this point and
is reflected back by the other turn toward ground. Due to this
construction the gaps to ground may be set approximately 50 per
cent, greater than the ordinary shunted horn gaps with the same
protection obtained.

For more severe lightning conditions the type of horn arrester
shown in Fig. 141 is used. This arrester is similar to the one
previously described except that a reactance coil is connected
in series with the high capacity resistance in the ground circuit.
An auxiliary horn gap shunts both the reactance coil and the
resistance thus giving a direct path to ground to a surge of such

LIGHTNING ARRESTERS

221

FIG. 140. — Railway & Industrial Engr. Co. lightning arrester type "WB.

FIG. 141. — Railway & Industrial Engr. Co. arrester with resistor.

222 SWITCHING EQUIPMENT FOR POWER CONTROL

capacity that it cannot be discharged quickly enough through the
reactance and resistance. This reactance is used principally to
relieve the resistance of the heavy strain by smoothing out the
surge before it reaches the resistance. The use of the reactance
coil in no way interferes with sensitiveness of the arrester.

S. & C. Horn Type. — Horn-gap arresters are also built by
Schweitzer and Conrad in the form of the graded resistance arrester
which consists essentially of a horn gap and a number of resis-
tance units so arranged that as the arc rises from the lower part
to the upper part of the horn, the resistance is automatically cut
into circuit step by step, so that the current is rapidly cut down
and the arc is easily broken when it reaches the upper part of
the horn. See Fig. 142.

ISOLATING
TUBES
CONTAINING
•ilASCE

FIG. 142. — Schweitzer & Conrad graded resistance lightning arrester.

With any potential rise on the line or apparatus protected by
the arrester, the arc will start across the smallest gap which has
all the resistance in series. If the potential rise is of low energy
capacity, the current flowing through this gap and total resistance
may be sufficient to keep the voltage down to approximately
normal. If the current flowing through this gap and resistance is
insufficient to keep the voltage down, the arc will break across the
next lower step and a larger current will flow. If this current is
still insufficient to keep the voltage down to safe value, then the
next lower step will arc across, etc., until the "no resistance"

LIGHTNING ARRESTERS

223

or lowest step is reached, when the system will actually be short-
circuited and practically unlimited current can flow.

Schweitzer & Conrad arresters are regularly furnished in a
number of combinations. By the addition of a choke coil, a
disconnecting switch, and a load fuse, a complete protective com-
bination can be made on one channel base, so that the installa-
tion of the whole combination is quite simple as compared to the
installation of separate pieces of apparatus. One of these ar-
rangements is shown on Fig. 143.

FIG. 143. — Schweitzer & Conrad protective combination.

Reactors. — Choke coils, in addition to being used for lightning
protection, are employed for the purpose of current limiting
reactors in large power plants, and have been connected in the
circuits of generators, feeders and bus bars.

In large systems current limiting reactors have been installed
for the purpose of limiting the amount of current that may flow
from any part of the system into a short circuit in the apparatus
or the connections inside the station or close to the station. By
so limiting the abnormal flow of current into a short circuit, the
generating system as a whole is relieved from the possible disas-
trous effects of short circuit. At the time of the disturbance on
the system the extra load thrown on the generators by the energy
fed into the short circuit is such that the generating frequency
and voltage are momentarily lowered and the reactors will tend
to reduce this extra load on the system and minimize the change

224 SWITCHING EQUIPMENT FOR POWER CONTROL

in frequency that often throws out of step the synchronous
apparatus in the. substations and the generators at other connect-
ed stations.

Some of the earlier turbogenerators particularly for 25-cycle
service, had a comparatively small amount of internal reactance,
but the manufacturers of turbogenerators are now recommending
a total generator reactance, internal and external, of from 10 to 15
per cent, and turbogenerators are now usually so designed as to
be able to withstand mechanically a dead short circuit across their
terminals with full field excitation. Arrangements are usually
made to build such turbogenerators with fairly high internal
reactance and to brace their coils sufficiently to withstand the
mechanical stresses set up at the time of short circuit.

Breakdowns. — Experience seems to show that a large percent-
age of the breakdowns originate in the feeder circuits, and the
use of feeder reactors for minimizing the trouble is employed
in many cases. These feeder reactors reduce the stresses upon
the circuit breakers, and frequently make it possible to use
smaller and cheaper breakers in moderate capacity plants
than would otherwise be possible. As the ratio of the feeder
capacity to the total station capacity in large plants is usually
small, a small percentage reactance on a small feeder reduces
the short-circuit current to practically a negligible quantity.
The small percentage of reactance also makes negligible the effect
of the regulation of the feeder.

With reduction in the feeder short-circuit current, the relay
system can be made far more selective, the voltage in the system
will not be materially affected, the energy fed into the short
circuit will not tend to slow the generators down, reducing a
change in the system frequency, and synchronous apparatus
on other parts of the system will not fall out of step. The
protected feeder will be automatically disconnected from the
system without interruption of service to the remainder of
the system.

Makers. — Current limiting reactors for various services have
been furnished to many of the largest plants by the Metropolitan
Engineering Company, the General Electric Company and the
Westinghouse Electric & Manufacturing Company.

Metropolitan Engineering Company Reactors.— The appear-
ance of the coils is clearly shown in Fig. 144, this showing
an installation of porcelain-clad reactors of the Metropolitan

LIGHTNING ARRESTERS 225

Engineering Company. The coil consists of a series of horizon-
tally wound spirals supported and insulated by porcelain arms
having suitable recesses for the winding. The arms are assembled
radially as vertical walls between a hollow core of concrete
or soapstone, and an outer enclosing wall built up of special
porcelain segments. These cellular compartments, so formed,
allow natural ventilation for the coil. The entire coil is supported
at the two ends by heavy concrete headers securely held by a

FIG. 144. — Reactor of Metropolitan Engineering Co.

number of brass bolts with insulating mica tubes passing through
the heads and wall of the special porcelain segments from top to
bottom. Ventilating holes are connected with each vertical
cellular compartment of the coils.

Porcelain Clad. — These reactance coils are porcelain clad,
and the windings are embedded at their supports in walls of
smooth porcelain insulators, giving fireproof construction with
good electrical and mechanical qualities entirely unaffected by
high temperatures. The smooth glazed finish of the porcelain
facilitates inspection and cleaning of coils, and the almost mono-
lithic construction insures mechanical safety.

Mutually Reactive Coils. — For combining in one unit the
protection desirable for the circuit of the generator bus bar and
feeder, mutually inductive reactors have been designed, these
consisting essentially of reactors with a tap in the middle, the
current being taken in at this point and taken out at the two
opposite ends as shown diagrammatically in Fig. 145. These

226 SWITCHING EQUIPMENT FOR POWER CONTROL

mutually inductive reactors protect the generator from excessive
short-circuit currents, protect and localize any trouble on a bus
section, and materially reduce the short-circuit current into
feeder troubles.

1M-HI IN

EP|EH IGRO|UP BJJ5 1 o o| 1

FIG. 145.

This combined system of coils is better than the independent
coils, in requiring much less space, in utilizing the mutual inductance
between the two sections of the coils to limit the current to a great-
er extent for a given amount of copper, and to reduce the short-cir-
cuit disturbance, as the current in the short circuit is made to
keep up the pressure on the rest of the system.

In all cases the reactance coils should be placed as close to the
bus as possible to protect the bus under the greatest number of
conditions, so that the reactance coils should be considered as a
part of and made as reliable <as the high tension bus.

Semi-porcelain Clad. — A modification in the construction
of these Metropolitan coils is known as the semi porcelain clad
reactor. With this arrangement the coils are made up of a num-
ber of concentric co-axial solenoids in parallel, designed to give a
uniform potential gradient from top to bottom. The insulating
space required between layers is practically eliminated, this
resulting in a large reduction in size and increased efficiency
of coils. While the coils are cylindrical they are assembled in
rectangular forms with porcelain insulators at the four corners,
these insulators being of L shape with micarta barriers passing in
front of the coils.

G. E. Reactors. — General Electric reactors are of the "cast in"
type, i.e., the windings are rigidly held in place by vertical con-
crete supports which are cast around the turns after the coil

LIGHTNING ARRESTERS

227

has been wound in a form built up of steel plates as shown in
Fig. 146. After the concrete has set, the forms are removed and

the concrete is cured by treating with high-pressure steam. This
method will give twice as much aging as would be obtained by

228 SWITCHING EQUIPMENT FOR POWER CONTROL

natural processes in several months. The reactor is then sand
blasted, thus giving both the copper and concrete a very finished
appearance as shown in Fig. 147.

The number of supports depends upon the current rating
and the stresses produced by short circuit current. Intimate
contact between the winding and the supports insures a very
rigid structure. There are no through bolts in the coil, and the
possibility of a short circuited winding due to arc over from the
terminals to the bolts is therefore eliminated.

iffir intent

*jjL$ ^5 25

'^ JHjF-*~ •l^^r «-* '^ - ' ~-~ -%~

t * ^^i

FIG. 147. — G. E. Co. "cast in" type power limiting reactors.

Windings. — The windings consist of one or more cables in
multiple. These may be solid or, if necessary, concentrically
stranded with asbestos paper between layers in order to keep to a
minimum the loss due to eddy currents.

The turns are wound radially in conical layers with adjacent
layers inclined in opposite directions. Ample spacing is provided
between turns and layers, depending upon the circuit voltage
and the K.V.A. capacity of the reactor. Any two adjacent layers
converge toward the point of interconnecting crossover, where
the voltage between layers is consequently equal to the voltage
between turns. All crossovers are embedded in the concrete
supports so that all of the cable exposed is concentric, and full
distance is maintained between turns at these points.

The terminals consist of heavy pressed copper tube brought
out radially or circumferentially from one of the coil supports.
The conductors are brazed into these terminals, thereby eliminat-
ing the possibility of an open circuit at these points, due to over
heating by short circuit current.

LIGHTNING ARRESTERS 229

If necessary the coil may be divided into two sections wound
in opposite directions, in which case the bottom end of the top
section and top end of the bottom section are usually brought
to the same terminals, and the other ends of the sections are
each brought to a terminal which is bolted to a vertical copper
bar or strap joining the two. Thus the coil is symmetrical
about a plane perpendicular to the mid point of its vertical axis.

Base. — The concrete supports are uniformly spaced around the
coil. They rest on a heavy concrete base ring having a rectangu-
lar cross section, which serves to distribute the weight of the
coil. The supports and base are bolted together by means of
bolts fitting into threaded thimbles cast in the bottom of each
support.

Insulators. — To insulate the structure from ground the base is
set on pedestal-type porcelains to which castings are fitted at
each end. The top castings are provided with tap holes in the
center by means of which they may be bolted to the base ring.
The bottom castings are provided with holes for bolting to the
floor.

Installation. — For a three phase installation, three single phase
reactors may be installed in a row, at the corners of an equilateral
triangle, or one above the other. When required by the magnetic
forces the reactors are braced from each other and from the wall
by means of corrugated porcelains which fit into castings attached
to the concrete columns. A three-phase reactor may also con-
sist of three separate windings one above the other, cast into the
same supports. Where space is available, the preferred method
however, is to install each reactor in a separate cell.

Shunting Resistance. — In some of the latest designs, the reactors
are supplied with shunting resistors connected across the termi-
nals of the coil. These resistors will absorb impulse voltages and
prevent the building up of excessive resonant voltages. Under
normal conditions, the loss in the resistor is very small, but
in case of high frequency surges, the shunting path is very
desirable in that it tends to dissipate the energy of the high
frequency oscillation. It is an interesting fact that these
resistors have the valuable property of high resistance at low
voltages and low resistance at high voltages. The resistors
consist of resistance rods embedded in concrete blocks which
are placed inside the reactor and rest upon the reactor base.

230 SWITCHING EQUIPMENT FOR POWER CONTROL

Westinghouse Reactors. — The current limiting reactors of the
Westinghouse Electric & Manuf acuring Company are built either
as single-phase units or as 3-phase. A typical single-phase coil
is shown in Fig. 148, this having a rating of 100 K.V.A., 1000
amperes, 25 cycles or 8 per cent, on the basis of a normal 3-
phase circuit, at 2200 volts with one coil per phase. As these

current limiting reactors are air
cooled a comparatively large area
of conductor surface must be
provided to dissipate the PR loss
and since the area of a conductor,
such as a cable, increases with the
square of the diameter and the
surface as the first power, it is
obvious that the smaller the
diameter of the cable the more
efficiently is the copper worked.
The copper represents the large
part of the cost of a reactor hence
the necessity to keep its amount to
a minimum. This reasoning has
led to the use of a fairly small size
of cable and the use of a number of
these in parallel to get the proper
current-carrying capacity.
Multiple Winding. — With a number of cables in multiple in a
coil of this kind there is a tendency for these parallel circuits to
have different ohmic and inductive characteristics unless special
precautions are taken to see that the lengths and relative posi-
tions of the cables in the parallel paths are practically identical.
If this is not done there will be circulating currents set up that
will cause excessive loss and heating of the coils.

Large Reactors. — With a typical single-phase Westinghouse
coil for use with a 3-phase generator of 21,100-K.V.A. capacity
the normal full-load current is 1100 amperes and the coils are
wound with seven stranded bare copper cables connected in
parallel in such a manner that the paths are of substantially the
same lengths and impedance. The seven cables are wound into
grooves in specially prepared moulded fireproof cleats These
seven cables enter the coils at seven equi-distant points around
the inner periphery of the bottom layer of the coil. The first

FIG. 148. — Westinghouse single-
phase reactor.

LIGHTNING ARRESTERS

231

cable occupies the inner circumferencial row of slots for one-
seventh of a turn and then passes out to the second row of slots
and the second cable occupies the inner row. These two con-
tinue in this position for the second seventh turn, at the end of
which they step outward one more row and the third cable enters
on the inner row.

The moulded cleats with slots into which the cable is wound
have holes in their ends through which brass rods covered by
insulating tubes are placed for clamping the layers together
securely. On the top and bottom of each tier of cleats is placed
a nonmagnetic metal cleat that allows the coil to be clamped

tightly together. The spacing be-

tween columns of cleats is close
enough to prevent any appreciable
deflection of the cable under the
most severe short-circuit conditions.
The tensile strength of the copper
in the cable is sufficient to resist the
magnetic stress tending to increase
the diameter of the coil.

Supports. — The coil is supported
on three nonmagnetic castings each
of which spans four tiers of cleats.
Into these castings are cemented
insulators which rest on metal pins
suitable for cementing or bolting to
the floor. Two brass rods pass
through the opening of the coil and
are supported by porcelain bush-
ings held in place by a three way
support and on each end of the rod
is provided a line terminal. All of
the cables at one end of the coil are

connected to one rod while the cables at the other end connect
to the second rod.

Three-phase Reactor. — For 3-phase feeder circuits of mod-
erate capacity a 3-phase reactor such as shown in Fig. 149
can be supplied. This shows a 440-ampere, 127-volt, 167-
K.V.A. 25-cycle, 3-phase coil for use on a 6600-volt circuit.
Such a coil gets the advantage of the mutual reactance between
phases and it may be noted that the coils at the top and bottom

FIG. 149. — Westinghouse three-
phase feeder reactor.

232 SWITCHING EQUIPMENT FOR POW^R CONTROL

are part of the same coil in one phase while the two wider coils
in the middle are for the remaining phases. Such 3-phase
coils can be installed in a much smaller space than three single-
phase independent coils and the wiring of the plant can fre-
quently be simplified by their use.

CHAPTER IX
REGULATORS

The switches, fuses, circuit breakers, relays, instruments,
etc., all have their important functions to perform as part of the
switch gear in a station but as practically all electrical energy
is distributed on the constant potential system, the devices
for maintaining constant potential are of vital importance in
any plant. Where the circuits are few and all of about the
same length and load conditions it is only necessary to maintain
constant the voltage on the bus bars. Where there are many
feeders with varying load conditions it becomes a matter of
importance to be able to adjust the voltage on these feeders
independently. The demand for this class of adjustment led
to the development of feeder regulators.

FEEDER REGULATORS

Step Type Regulator. — The first type of regulator was a
transformer with many taps and provision for connecting the
feeder to any tap. This could be done by switches of various
kinds and the natural development was to arrange the contacts
in the form of a ring on a suitable faceplate and to provide a
movable arm for connecting the feeder to any of the taps from
the transformer. As the voltage was varied by definite steps, this
type of regulator was known as the step type regulator. These
regulators consist essentially of a dial or drum with a number
of contacts or steps, connecting to taps brought out from
the secondary of a transformer whose primary is usually connect-
ed across the feeder circuit. This feeder circuit is connected
in series with the dial and a reversing switch so that a part or
all of the secondary voltage of the transformer can be added to
or taken from the bus voltage.

Reverser. — The moving arm on the dial type regulator is
usually arranged so that in passing from the position of maximum
boost the number of secondary turns in series with the circuit
is reduced in equal steps until the turns are all cut out. Further
rotation in the same direction throws over the reversing switch

233

234 SWITCHING EQUIPMENT FOR POWER CONTROL

and then cuts in the same secondary turns in opposition to the
main voltage until the position of maximum buck is reached,
when a stop prevents any further rotation in that direction. A
similar stop prevents overtravel in the position of maximum
boost

Split Arm. — With this dial type regulator the contacts are
mounted on a marble dial and a movable arm, spring actuated,
is so arranged that it moves quickly from step to step without
any possibility of stopping between steps and short-circuiting
a part of the transformer. A modification of this arrangement
has the contact arm split in two parts with a preventive resistor
or reactor joining the two parts to obviate any chance of short-
circuiting part of the transformer.

Limits. — For high voltage or heavy current capacity the step
type regulator can be employed by the use of current or po-
tential transformers or both, so that the current to be handled
does not exceed 200 amperes and the voltage on the dial is not
greater than about 2200 volts or about 440 K.W. maximum for
the capacity of the feeder on which 20 per cent, regulation or
88 K.W. can be obtained.

For heavy service on circuits up to 6600 volts and for handling
a greater voltage per step than the 20-25 that can be taken
care of with an open air dial, a drum-type regulator is used having
its switch and contacts immersed in oil. Regulators of this type
can be built for 6600 volts, 200 amperes, 20 per cent, regula-
tion or about three times the capacity of the dial type. For some
classes of electric furnace work the drum-type regulator or a
step by step device is employed with an induction regulator to
give a smooth and continuous variation in voltage between steps.

Induction Type. — In most modern installations the induction
regulator is used in preference to the step type as giving a more
even adjustment of voltage, avoiding any winking of the lights
and allowing for automatic operation in a simpler manner
than the step type.

Induction type regulators are made for single-phase or 3-
phase service and arranged for hand operation or motor oper-
ation, or motor operation controlled from a distant point, or
for complete automatic operation by means of relays. The
regulator for single phase circuits consists of a rotatable primary
core and winding and a fixed secondary core and winding usually
immersed in oil. The primary winding is connected across

REGULATORS

235

the line and the secondary is in series with the feeder. The
voltage induced in the secondary depends on the relative posi-
tion of the two coils and increases or decreases the feeder voltage
by a practically infinite number of steps.

Where automatic operation is desired for either single or
3-phase regulation this is obtained by the action of a voltage
relay either with or without a compensating device. This
relay acts in conjunction with the motor on the regulator in
such a way that as the load comes on or as the bus voltage drops
the motor will turn the regulator in such a direction as to increase
the voltage. By means of a compensator, which can be set
for a certain ohmic and a certain inductive drop, the voltage at
the point of distribution can be maintained constant, independent
of the amount and power factor of
the load if the total drop is within
the range of the regulator.

While the illustrations and de-
scriptions of induction regulators
that follow are based on Westing-
house apparatus, the regulators made
by the General Electric Company
have many of the same features and
the descriptions with slight modifi-
cations would apply in most cases to
the General Electric devices.

Single phase Type. — Fig. 150
shows a motor operated single-phase
induction type regulator with the
tank removed.

The regulation of feeder voltage is
accomplished by turning the rotor,
either by hand or electrically, so as
to change the relation of the rotor
winding to the stator winding. The
regulation is smooth and gradual in

FIG. 150. — Westinghouse sin-
gle-phase motor operated voltage
regulator.

either direction throughout the entire range of the regulator.
The circuit is not opened at any point, the effect of the
regulator being practically the same as would be obtained by
changing the generator voltage.

The single-phase regulator is in effect a two-winding trans-
former, with the secondary winding arranged for connection in

236 SWITCHING EQUIPMENT FOR POWER CONTROL

series and the primary winding arranged for connection directly
across the line. With a transformer thus connected a voltage
will be induced in the secondary that will add to or subtract from
the feeder voltage according to the connections used.

Action. — With the regulator, the primary winding is the
movable winding (the rotor) and the secondary the stationary
winding (the stator). The current in the primary produces a
magnetic field that induces a voltage in the secondary. The
portion of this field passing through the secondary winding and
consequently the voltage induced in that winding, depends upon
the angular position of the secondary with respect to the direc-
tion of the primary field. The induced voltage is a maximum
when the axes of the coils coincide; zero when the coils are at
right angles to each other; and maximum in the opposite direc-
tion when the axes of the coils coincide but with primary coils
reversed in position. This induced voltage in the secondary,
therefore, adds to or subtracts from the feeder voltage by a
value varying from maximum regulation to zero, according to the
position of the coils.

Short-circuited Winding. — It is evident that a magnetic field
is also set up by the line current flowing through the secondary
windings (stator coils) which, if not neutralized, would produce a
choking effect and lower the power factor in the feeder circuit.
This choking effect would occur whenever the primary winding
(rotor) is in any position other than where the axes of the two
windings coincide — the positions of maximum "buck" or
'"boost" — being minimum near these positions and maximum
when the axes of the two windings are at right angles to each
other — the neutral positions. To overcome this choking effect,
a short-circuited winding is placed in partially closed slots in the
rotor core and at right angles to the primary coils; this short-
circuited winding acts as a secondary to the stator coils and
neutralizes their choking effect. By using a large number of
turns of relatively small insulated wire in the short-circuited
winding, the choking effect is neutralized with a comparatively
small copper loss in the short-circuited winding.

Polyphase Regulator. — This regulator may be likened some-
what to a phase-wound polyphase motor. The regulator pri-
mary (rotor) is wound with a distributed winding of the same
number of phases as there are phases in the feeder to be regulated
and each phase is connected across a separate phase of the feeder.

REGULATORS

237

The regulator secondary (stator), is made up of separate wind-
ings of the same number as the primary, and each of these separ-
ate windings is connected in series with one of the feeder wires.

Action. — The primary sets up a magnetic flux of constant
value, which induces a constant voltage in each of the secondary
windings. The induced voltage is added therefore vectorially
to the feeder as the cosine of the angle between windings. As
the position of the rotor is changed, the phase angles between the
feeder voltage and the secondary voltage correspondingly
changes, and the feeder voltage is either increased or decreased
as the phase angle is less or greater than 90 degrees.

Since the polyphase regulator has windings distributed around
the entire circumference of the rotor, these windings will also
act as neutralizing windings for the
various stator windings and no sep-
arate short-circuited windings, as in
the case of single-phase regulators, are
necessary.

Motor Drive. — In the standard
regulators, the rotor is turned by a
small alternating-current induction
motor driven through a pinion, spur
gear, worm, and worm segment (see
Fig. 151). The motor is controlled
non-automatically by a hand operated
switch, or by an electrically operated
switch with push-button control
mounted in any convenient location;
or automatically by means of relays
and other accessories especially made
for the service. The motor operated
regulators are equipped with a hand
wheel to operate them by hand in case of failure of the control
circuit.

A relay switch is used to control the motor circuit so as to
relieve the contacts of the primary switch from the necessity of
carrying the current required to operate the motor. On the
Westinghouse regulators this relay switch, called the secondary
relay, is operated by a control circuit closed through a hand
operated switch when non-automatic operation is used, a push-
button switch generally being used — or through a primary relay

FIG. 151. — Westinghouse
polyphase induction regulator
motor operated.

238 SWITCHING EQUIPMENT FOR POWER CONTROL

when automatically operated. It is essentially an electrically
operated double-pole double-throw switch.

Limit Switch. — This is connected in the operating circuit
and actuated by the operating mechanism of the regulator,
prevents overtravel of the rotor in either direction. It is com-
bined with the secondary relay when that relay is mounted
on the regulator top-cover; and when the secondary relay is
mounted separately the limit switch is mounted directly on the
regulator top-cover.

Primary Relays. — The voltage regulating primary relay is in
effect a voltmeter having two sets of contacts that control the
circuits operating the secondary relay, one circuit being closed
when the voltage rises above a predeter-
mined value and the other when it falls
below another predetermined value.

The primary relay shown in Fig. 152 is
enclosed in a metal case with dustproof
cover provided with a window permitting
ready inspection of the operating parts.
It has compounding coils so that as soon
as a change in voltage causes either set of
contacts to close they do not "chatter"
but remain closed until the voltage returns
to normal. Means are provided for ad-
justing the relay for different voltage
variations and ranges.
No-Voltage Device. — A special primary relay having a no-
voltage device can be supplied to cause the regulator rotor to be
turned to the position of minimum voltage in case the power
supply in the feeder circuit is interrupted. It, therefore, prevents
the possibility of temporary overvoltage on the circuit when the
power supply is again continued. A voltage transformer of the
proper rating is used to reduce the feeder voltage to a value suit-
able for the primary relay. A compensator is a device connected
to the feeder circuit at the station by means of a current trans-
former, and in connection with a voltage transformer, produces
at the primary relay terminals a voltage proportional to that at
the distributing end of the feeder.

Outdoor Type for Platform Mounting. — The outdoor induct-
tion feeder voltage regulators shown in Fig. 153 provide a means
of obtaining good voltage regulation in outlying districts or on

FIG. 152. — Primary
relay for induction
regulator.

REGULATORS

239

any other part of an alternating-current distribution system
without the expense of housing — they fit in well with the other
apparatus now being used so economically in outdoor substations
and other outdoor installations.

Being entirely weatherproof and self-contained these regulators
may be mounted on platforms con-
structed on poles or on the ground,
protected by a fence or screen, in
the same manner as transformers
in outdoor substations. The only
attention required is a general in-
spection for oiling the motor bear-
ings and worm-screw mechanism,
filling grease cups, and examining
the relay contacts at regular
intervals.

Mounting. — These regulators are
made for mounting on any sub-
stantial flat surface, such as a
platform between poles or on a
platform on the ground ; lifting lugs
are provided on the sides of the
housing for raising the regulator to
the platform. As they are not in-
tended for suspension from cross-
arms, they are not provided with FlG. 153._Outdoor type induction

mounting tugS. regulator — cover raised.

FIELD RHEOSTATS

Rheostat. — For regulating the current in the shunt fields or
separately excited fields of A.C. and B.C. generators and motors,
it is customary to use field rheostats made up of faceplates and
resistors of suitable design. The faceplate comprises a series
of contacts, usually 20, 24, 40, 48 or 60, arranged in a circle
mounted on a slate or marble base and provided with a movable
contact arm. Stops on the faceplate limit the travel of the
contact arm which is usually of the flat lever type up to 75
amperes and finger contact for larger, and is mounted on a shaft
and operated either by a handwheel placed directly on the shaft
or operated from a distance through sprocket and chain, bevel
gears, solenoids or motors. With small A.C. generators having

240 SWITCHING EQUIPMENT FOR POWER CONTROL

their own exciters, concentric handwheels, shafts and operating
mechanisms are frequently provided for the generator and exciters
Distant Control. — There are various advantages to be obtained
by mounting the rheostat at a distance from the switchboard,
the main ones being the removal of the heat producing resistors
from the immediate neighborhood of the switchboard and the
possibility of placing the faceplate close to the resistors. In
moderate capacity plants, sprocket-chain and wire-rope trans-
mission is customarily employed for connecting together the
handwheel on the switchboard and the faceplate near

the resistors and their re-
lative location can be made
to suit the station require-
ments.

In very large stations
where electrical operation
is applied to the oil circuit
breakers, the field rheostat
faceplates are usually made
solenoid operated in the
smaller sizes and motor
operated in the larger.

Solenoid Control. — Fig.
154 shows a typical ar-
rangement of a 48-step
solenoid operated faceplate
mounted on grid resistors.
The operating mechanism
and contacts are covered
by an iron shield, sufficient
space being left to allow
for inspection, and a hand-
wheel being provided for
hand operation. The sol-
enoid mechanism consists of two electro magnets, a ratchet wheel,
two pawls, a make and break switch and the necessary levers
and springs.

Motor Control. — For larger capacities a motor operated face-
plate, such as shown in Fig. 155, is employed. This type of face
plate is provided with a clutch so that in case of trouble to the
motor, the faceplate may be operated by hand, after disengaging

FIG. 154. — Solenoid operated field rheostat.

REGULATORS

241

FIG. 155. — Motor operated field rheostat
face plate.

the clutch. With this faceplate a signal switch is provided to

light up a lamp on the switchboard when the contact arm is

bridging two contacts. This faceplate is also provided wi'th

limit switches that open up

the control circuit when the

contact arm has reached the

limit of its travel in either

direction. The connections

are so made that while the

rheostat can no longer be

operated in one direction it

can be operated in the other.

Resistors. — Modern rheo-
stat resistors are usually
either of the bar form or the
grid form. The bar form
consists essentially of an
iron bar covered with a
suitable insulation and
wound over with a wire of
varying sizes so that with a

bar 1 inch by ^ inch in section, the resistance per linear inch of
bar can be varied from 0.03 to 400 ohms, with a maximum
capacity of 4 watts per linear inch.

Grids. — For heavier capacities grid resistors are employed,
these being made of cast iron of considerable mechanical strength
and high thermal capacity. These grids are cast in various shapes
to secure the desired resistance and are assembled on insulated
rods and clamped together, being connected in series or multiple
as required.

GENERATOR REGULATORS

Generator Regulation. — The earliest plants with poorly regula-
ting generators were only able to maintain proper voltage by
depending on the switchboard operator to continually adjust the
voltage by means of the rheostat. To reduce the amount of
adjusting, generators were made with very good inherent regula-
tion and various schemes were developed to get the equivalent
of a compound winding on an A.C. generator. These generators
with close inherent regulation were expensive to build and their
windings were difficult to brace against the effects of short cir-

242 SWITCHING EQUIPMENT FOR POWER CONTROL

cults so the trend of generator design turned to generators with
high reactance and poor inherent regulation, as soon as a satis-
factory regulator had been developed for maintaining the A.C.
voltage at its proper value under conditions of varying load.

Tirrill Regulators. — In order to maintain practically constant
voltage on A.C. and D.C. generators, or to have those machines
compound automatically to take care of feeder drop, field regu-
lators of various kinds have been designed, the best known being
the Tirrill.

While Mr. Tirrill has been connected at one time with the Gen-
eral Electric Company and later with the Westinghouse Electric &
Manufacturing Company working on regulator designs, he has
not been with either company for a number of years, and many
of the features of the regulators were due to the ideas of other
engineers at these two companies. His name has been so closely
connected with the development of this type of voltage regula-
tors that most engineers not connected with the two manufac-
turing companies are still apt to speak of the regulators as a
"G. E. Tirrill" or a "Westinghouse Tirrill" although neither
company uses the name "Tirrill" in describing their regulators.

A.C. Regulators. — The various uses to which alternating-cur-
rent voltage regulators are best adapted fall into the following
divisions : (a) the maintenance of constant voltage at generator,
bus, or some predetermined center of distribution; (6) the main-
tenance of constant voltage at the end of transmission lines by
the control of synchronous condensers or synchronous boosters;
(c) the control of booster-type rotaries; (d) the control by special
regulators of synchronous condensers applied to local network
or distributing systems for voltage regulation and power factor
correction; and (e) the maintenance of constant current instead
of constant voltage.

D.C. Regulator — G. E. Type. — For direct-current service
the G. E. regulator consists essentially of a main control magnet
with two independent windings and a differentially wound relay
magnet with connections about as shown in Fig. 156. The
potential winding of the main control magnet is connected across
the generator terminals and the other winding across a shunt in
one of the load mains. This opposes the action of the potential
winding and makes the generator over compound for line drop.
The main features of the diagram are self evident. When the
effect of the potential winding diminishes, due to drop in volt-

REGULATORS

*•»*«•*

243

«««*«• •**•+»*•••.:

TO- if 5 /OS /JO I/S /20 IZS

ra-sjo sso
FIG. 156. — G. E. voltage regulator for D.C. machines.

Current
Transformer

FIG. 157. — G. E. voltage regulator for A.C. machines.

244 SWITCHING EQUIPMENT FOR POWER CONTROL

age or increase in load, the spring lifts the main contact which
in turn energizes the relay magnet closing the relay contact, thus
short-circuiting the generator rheostat and raising the voltage.
The relay contacts are shunted by a condenser to reduce the
sparking.

A.C. Regulator — G. E. Type. — With A.C. generators, that are
almost invariably separately excited, the G. E. regulator works
on the exciter field as shown in the simplified diagram of con-
nections in Fig. 157. The main contacts with this type of regula-
tor are acted on by two sets of control magnets, one connected
across the exciter bus and tending to move the main contacts
further apart as the exciter voltage rises while the other control
magnet is acted on by an A.C. potential coil and current coil
while suitable springs and counter weights allow the proper ad-
justments to be made. When the main contact closes it energizes
the relay magnet, closing the relay contact, short-circuiting the
exciter rheostat and raising the exciter voltage and consequently
the generator voltage.

Compensation. — As may be noticed from the diagram the com-
pensating winding is provided with a dial switch to give any
amount of compensation required for the feeder circuit in which
the current transformer is located. Where it is desired to com-
pensate for both ohmic and inductive drop under varying power
factors a special compensator is provided. A modification of the
regulator to take care of larger exciters has a plurality of relay con-
tacts, all operated at the same time from the one set of control
contacts, the various relay contacts being shunted by condensers
to reduce the sparking.

D.C. Control. — The features of the G. E. regulator, that have
been so conducive to its successful operation, are the method of
control adopted and the fact that with the total range of regu-
lation from no-load to full-load the maximum travel of the only
moving parts, the vibrating contacts, is only 3^2 inch. The
vibrations are so rapid that the time factor is reduced to the mini-
mum possible limit and there are no retarding effects due to dash-
pots or other damping devices. The use of the exciter voltage
as one of the main control circuits also prevents overshooting for,
as the exciter voltage rises to bring up the A.C. voltage, the D.C.
control tends to keep the main contacts apart and so reduce the
voltage again.

REGULATORS

245

Westinghouse. — Westinghouse voltage regulators, arranged
in a suitable case, are constructed for bracket, panel, or pedestal
mounting, as required by installation conditions. Bracket
mounted regulators are provided with a standard black-marine
slate base.

The regulator parts as shown in Fig. 158 are arranged in the
case with the control system located in the upper part supported
on a small cast base, and with
the rheostat shunting relays ar-
ranged in horizontal rows at the
bottom. The control element
and relays are self-contained
units and either may be re-
moved from the base without
disturbing its adjustment.

Control. — The control system
for alternating-current and sep-
arately excited direct-current
generators consists of the main
control magnet and the vi-
brating magnet, with the main
contacts between them. The
magnets are of the solenoid
type, and are very sensitive.
They are provided with ad-
justable dashpots to permit
adjustment of regulation to
suit the characteristics of the
system.

Vibrating Relay. — One of the relays, called the vibrating
magnet relay, is used to govern the operation of the vibrating
magnet. On the larger size generators, one or more master
relays are used to control a group of rheostat shunting relays,
thus relieving the main contacts of handling control circuits
beyond their capacity.

Master Relay. — The use of the master relay is made possible
by the alternating-current control and permits of the construction
of regulators with as many as 60-rheostat shunting relays. The
master relay introduces no time lag in the response of the regu-
lator, nor in the voltage regulation, since the vibrating magnet
relay and the rheostat shunting relays operate simultaneously.

FIG. 158. — Wcstinghouso automatic
generator voltage regulator.

246 SWITCHING EQUIPMENT FOR POWER CONTROL

Action.— Referring to Fig. 159 the main control magnet has
its core attracted upward. Its core stem is connected to the
floating lever, which is pivoted to the bell-crank lever of the
vibrating magnet. A counterweight is used to assist the pull
of the main control magnet, and to bring the lever and core to
a balanced position at the normal voltage to be regulated. The
vibrating magnet also has its core attracted upward. Its core
stem is connected to one end of the bell-crank lever which is
pivoted to the base, and its opposite end carries the floating
lever of the main control magnet. The pull of this vibrating

Main Contacts
Main Control

Pivot

'Voltage Limiting Rheostat V. C Field Rheostat

FIG. 159. — Westinghouse voltage regulator diagram.

magnet is assisted by a single spring as shown. These two mag-
nets are energized from the same voltage transformer, and actuate
the movable main contact into and out of engagement with the
fixed contact.

Diagram. — An inspection of the schematic diagram shows
that the closure of the main contacts causes all relay contacts
to close. One of the relays, called the vibrating relay, is con-
nected so that the closure of its contacts shunts a small portion
of the resistance in series with the vibrating magnet, thus increas-
ing its pull and opening the main contacts. The opening of
the main contacts open all relay contacts and inserts the full
resistance in the vibrating magnet circuit, weakening the pull
and closing the main contacts again.

From the above cycle, it is seen that for any given position
of the floating lever, a condition of continuous vibration results.

REGULATORS 247

A necessary condition to the continuous vibration of the system
is that the weight of the vibrating magnet core and lever must be
exactly balanced by the tension of the control spring and average
pull of the magnet. Any change in the tension of the control
spring results in an equal change in the average magnet pull.
For a given line voltage there is a definite magnet pull when
the contacts are closed, and a definite pull of less value when
the contacts are opened. The average magnet pull must be a
function of the time of the contact engagement. For any given
position of the floating lever, there is a corresponding position
of the bell-crank lever and tension of the control spring. How-
ever, on account of the balanced condition there must be a
corresponding average magnet pull and time of contact engage-
ment.

Rheostat Shunting Relays. — The contacts of these relays
open and close across the shunt field rheostat of the exciter, and
the effective resistance of the rheostat is determined by the time
of contact engagement. For any effective resistance, there is
a corresponding exciter voltage, and, therefore, A.C. voltage.

A.C. Control. — As the control element is energized from the
A.C. generator the main control magnet will assume a position
such that a time of contact engagement is maintained sufficient
to develop an exciter voltage and, therefore, an A.C. voltage
capable of balancing the core weight. Any variation in line
voltage changes the position of the floating lever in such a
manner as to vary the excitation and restore the balance.

There are many interesting features such as the equalizing
rheostats used with two or more exciters, the overvoltage
relays to guard against trouble from excessive rise of voltage
if a contact should stick which cannot be more than mentioned
in this place.

For further details regarding the methods of operation, the
cutting of the regulator into and out of service, the securing
of line drop compensation, the parallel operation of voltage
regulators, reference should be had to the manufacturers' cata-
logues, instruction books and similar publications.

Application. — The successful application of voltage regulators
depends on several factors entirely independent of the size and
design of the regulator itself. It is not only necessary that the
regulator be properly designed, but it is also essential that the
exciters, generators, and prime movers possess characteristics

248 SWITCHING EQUIPMENT FOR POWER CONTROL

that will harmonize with each other and will assist in keeping the
voltage at the desired value under rapidly changing load condi-
tions. In general, the following conditions should be approached
as nearly as possible in order to obtain satisfactory reults :

1. Prime movers must be provided with proper automatic
governors that will respond instantly to changes in load and keep
the speed reasonably constant (within 3 percent to 4 percent
from no-load to full-load).

2. Alternating-current generators should have as nearly as
possible the same percentage range of excitation from no-load to
full-load.

3. Exciters must be capable of delivering sufficient voltage to
take care of the alternating current generator fields under full-
load conditions, 80 per cent, power factor, plus a certain additional
voltage. This additional voltage above the steady exciter volt-
age required to maintain constant bus voltage under full-load con-
ditions, is necessary in order that the regulator will continue to
vibrate and thereby have control of the exciter.

4. Exciters (where more than one are to be considered)
must be adjusted to operate in parallel under all loads and at any
point of the saturation curve.

5. Exciters for 125-volt service should be able to build their
voltage up or down between the limits of 30 and 125 volts in 5
seconds or less under load consisting of generator field circuits.
The time constant should be the same for exciters of other rated
voltages over proportional ranges. Exciters with greater time
constants than this may not permit the regulator to maintain
constant voltage with rapidly fluctuating load.

6. 125-volt interpole exciters must be able to develop at least
135 volts with the series winding disconnected, and should be so
operated. The series winding must be cut out of circuit in order
to secure a satisfactory time constant. In general, the exciter
must be capable of developing a voltage 10 to 15 per cent, in
excess of that required by the A.C. generator at full-load, 80
per cent, power factor, the A.C. generator field rheostat being
adjusted so that with 60 volts on a 125-volt exciter the A.C.
generator develops normal voltage at no-load.

Flicker. — On small systems, supplying a mixed lighting-and-
power load, where induction motors are sometimes thrown direct-
ly on the line without starting devices, the momentary current
required may be of such a value as to affect the feeder system and

REGULATORS 249

cause a noticeable flicker in the lights. Automatic regulating
devices in the generating station cannot be made sensitive enough
to prevent this effect under such conditions.

Voltage Adjusting Rheostats. — Taps are always provided
on the external resistor whereby the voltage regulated can be
varied from 104 volts • secondary to 116, in steps of 6 volts.
Where, for any reason it is desired to vary the operating voltage
of the system from time to time, a voltage adjusting rheostat
should be used in the control element circuits for the fine adjust-
ment of voltage, instead of varying the counterweight. This
rheostat has a sufficient resistance to give an adjustment
of about 6 volts either way from the normal voltage when properly
applied. The use of this rheostat is recommended in all applica-
tions, as it is a much more convenient and satisfactory method of
adjusting the voltage while the regulator is in operation.

Single Operation of Exciters and Parallel Operation of Gen-
erators.'— By the use of a control element energized entirely
from the A.C. system, the operation of alternating-current gen-
erators in parallel with the exciters operating singly, has been
made possible. The regulators for such service are equip-
ped with special transfer switches so that the D.C. circuit for
energizing the relays may be transferred to any exciter that
may be in operation.

Compensation. — For complete line drop compensation, it is
necessary to consider two factors, namely, inductive drop and
ohmic drop in the line and transformers between the generator
bus and the distributing center. The inductive component of
line drop is at right angles to the load current and is compensated
for by introducing into the potential circuits of the regulator a
voltage in phase with and proportional to the actual inductive
drop. An external compensator, energized from series trans-
formers, properly connected, accomplishes this purpose. This
compensator is provided with adjustable dials by means of which
the voltage introduced in the regulator circuits, for a given am-
pere load, may be varied, thus permitting adjustment for the
percentage inductive load.

The ohmic component of line drop is in phase with the load
current and is compensated for by energizing the current
windings of the regulator coils from series transformers properly
connected. The regulator control magnets are then affected
by a magnetizing force which is in phase with the load current.

250 SWITCHING EQUIPMENT FOR POWER CONTROL

The current windings on the regulator coils are divided into sec-
tions and connected to an adjustable dial. This provides a
ready means of obtaining the proper percentage of ohmic com-
pensation. Fig. 160 shows the connections to 3-phase systems
for this method.

Direction ot Power -•••

The obovt connections are correct 'or a secondary operating voltage of HO Volts II a HI-
ferent operating vo"o<jf is required, refer to the diagram of connections fumistno' with
the Vol'oge Aft lusting ffheostol 'or the proper connections to tn* C'ltrngl ren'stor

FIG. 160. — Compensator connections for regulator.

To obtain complete line drop compensation it is necessary to
adjust both the compensating devices to agree with the line char-
acteristics. Where ohmic line drop compensation only is desired
no external compensator is necessary. The current windings on
the regulator coils, when properly energized from series trans-
formers, accomplish this result. For 3-phase systems, two
current transformers in vector parallel are required for complete
compensation. The transformers must be in the same legs of the
circuit as those to which the voltage transformer is connected in
order that the resultant current will be in phase with the voltage
at 100 per cent, power factor.

Parallel Stations. — Where stations operate in parallel, and each
is controlled by a voltage regulator, it is possible to compensate
for the ohmic drop only, as inductive compensation destroys the
stability of the system. The point in the system at which it is
desired to maintain constant voltage should be determined
in order to obtain proper compensation.

Condensers. — These are required for connection across the
rheostat shunting relays, to minimize the contact wear occa-
sioned by the sparking incident to the opening of the shunt across
the exciter field rheostats.

REGULATORS 251

Exciter Rheostats. — When a regulator equipment is being
added to a plant in operation, the existing exciter rheostats should
be checked to determine whether they have sufficient resistance
to permit of adjusting the exciter for the proper time constant.
If not, new exciter rheostats must be provided. If the shunt
field rheostat of the exciter used for hand control is unsuitable for
use with the regulator, it can in many cases be used as the voltage-
limiting rheostat.

Auxiliary Exciter Rheostats. — Where two or more exciters,
operating either singly or in parallel, are controlled from a
regulator, the use of an auxiliary rheostat is required in the field
circuits of each exciter to adjust the time constants and maxi-
mum voltage of all the exciters to the same values in order that
they will carry their proper share of load. Where only one
exciter is controlled by a regulator the use of an auxiliary rheostat
is not required unless too high a maximum voltage and, conse-
quently, too large a field current, is obtained when the main
exciter rheostat is short-circuited by the relay contacts.

Voltage Transformers. — These of 400 volt ampere capacity
with fuse blocks and fuses are required for all alternating-cur-
rent voltage regulators.

Current Transformers are required only when compensation
for line drop in some particular circuit is desired, or when two or
more regulators are operating in parallel. One current trans-
former is required for partial compensation or two for full com-
pensation, and one transformer is necessary for each regulator
where two or more regulators operate in parallel. No current
transformer is necessary when it is desired to maintain constant
bus voltage.

Voltage Rise. — With the ordinary type of generator voltage
regulator, when a short circuit on a system is cleared away, a
dangerous voltage rise is inevitable. On the occurrence of a
short circuit on a system without some protective device, the
main contacts of the regulator close, causing the relay contacts to
close and the exciter voltage to build up to the maximum value.
When the short is cleared away, a high voltage results, due to the
high exciter voltage and consequent high generator field current,
which lasts until the regulator has had time to again become
operative.

Excess Voltage Device. — This condition of excessive voltage
can be prevented by means of the excess voltage protective

252 SWITCHING EQUIPMENT FOR POWER CONTROL

device, which can be applied to any Westinghouse A.C. regulator.
A diagrammatic view of this device is shown in Fig. 161. It
consists of an undervoltage relay in combination with a direct-
current control element connected in the main contact circuit of
the alternating-current voltage regulator. The contacts of the
D.C. element and the relay are connected in parallel, the pair
being in series with the main contacts of the regulator. The
D.C. element is energized from the exciter bus, and the relay
from the potential transformer supplying the A.C. regulator.

Main Contacts of Regulator

FIG. 161. — Excess voltage protection for regulator.

A short circuit coming on a system equipped with this protec-
tive device immediately causes the main contacts of the regulator
to close and the A.C. relay contacts to open, on account of the
drop in the A.C. voltage. As soon as the exciter voltage builds
up to the point for which the D.C. element is adjusted, the con-
tacts of this element begin to operate and to regulate the exciter
voltage in the same manner that the regulator contacts normally
do, so that the exciter voltage can never rise above the predeter-
mined point, which is usually a little above the no-load excitation
value required by the A.C. generators. When the short circuit
is relieved, therefore, no excessive field current exists to produce
a dangerous rise in A.C. voltage. The moment the A.C. voltage
rises above the setting of the undervoltage relay, the contacts
of the relay close and put the A.C. voltage regulator back into
service.

Battery Control. — Where storage batteries are used in a power
plant it is ordinarily necessary to provide some means of keeping
a fairly constant voltage on the D.C., bus bars or constant

REGULATORS 253

load on the generators independent of the condition of charge of
the battery or load on the feeder circuits. As the usual lead cell
when fully charged has a voltage of 2.5 per cell and as it is safe to
discharge a battery down to about 1.75 volts per cell it is evident
that some means must be provided to take care of this range of
voltage.

While end cell switches are used to a certain extent, the end
cells are only in service part of the time and do not get the same
service as the rest of the battery. In order to work all of the
cells the same amount it is customary to install a booster whose
voltage added to or taken from that of the battery will give the
desired pressure on the bus bars. Without going deeply into
the design of the battery or the booster it may suffice to say that
boosters usually have their armatures connected in series with
the battery across the bus while the field circuit on the booster
may be series, shunt or separately excited.

In order to avoid the necessity of hand regulation of the booster
voltage many very ingenious regulating schemes have been
devised and regulators make these schemes effective and enable
the voltage of the booster to automatically change in direction
and amount so as to enable the battery to charge, discharge or
float on the line.

CHAPTER X
INDUSTRIAL CONTROL APPARATUS

While it is not the intention of this book to go deeply into the
question of industrial control apparatus these devices are so
frequently used in connection with other switching equipment for
the control of the automatic substations or of motors in a power
plant that it is necessary to give some short descriptions of some
of the devices most frequently used in connection with the other
switch gear devices.

It is difficult to draw a very definite line in some cases between
control apparatus and switching equipment for power control
but the former may be considered primarily as intended for
motor control while the latter is used for power plants and general
distribution. Control apparatus is designed for severe service
and very adverse conditions and ruggedness is its essential
characteristic, with appearance considered usually of minor
importance.

Apparatus. — Some of the devices such as contactors, controllers,
starters, etc. will be considered in a rather brief fashion as a
full discussion would go beyond the province of this book and
should be reserved for a book dealing particularly with that
subject.

Contactors. — Contactor switches or contactors might be de-
scribed as switches or circuit breakers requiring some auxiliary
source of power, such as a solenoid or compressed air to hold
them in the closed position. They are used principally for
motor control and are designed primarily for multiple unit
control of railway motors and automatic or semi-automatic
control of industrial motors. These contactors are made in
many forms by different companies and except for the electro-
pneumatic system of multiple unit train control are usually
made solenoid operated and frequently provided with magnetic
blowout attachments.

254

INDUSTRIAL CONTROL APPARATUS

255

FIG. 162. — Con-
tactor switch.

Typical Design. — In the design illustrated in Fig. 162 the
contactors are built in sizes up to 1250 amperes D.C. and they
consist essentially of a contact that is closed by the action of a
solenoid which raises its plunger vertically when the coil is
energized and allows it to drop back by gravity
assisted by springs when the coil is de-
energized. The main contacts are above the
solenoid and are protected by magnetic
blowout coils which are so placed on each
side of the main contact that the arc is forced
quickly to the front and blown out. In
this design the main contacts are of the butt
type, the lower portion being moved by the
plunger and the upper portion being fixed
either rigidly or with a slight spring motion.
The main contacts in the larger sizes are
double, the arcing tips being made of brass
and being readily renewable and the other contacts being of
copper.

Interlock Contacts. — These contacts located below the solenoids
consist of flat brass discs carried on an insulating rod attached
to the lower end of the plunger rod, these rings making contact
against copper blocks attached at the outer ends of insulating
supports hung down from the contactor. These interlocking con-
tacts carry only the small amount of current required for the
magnet coil. These contacts can be readily arranged to secure
practically any scheme of electrical interlocking that may be
desired and to insure the closing of a series of contactors in any
predetermined sequence.

Master Switch. — These contactors are ordinarily used in
connection with a master switch or controller and protective
relay switches of various kinds to insure the performance of vari-
ous functions, such as the automatic cutting in and out of
resistance in the secondary of an induction motor; to maintain
constant input to a flywheel set; or any similar features that may
be desired.

Controller. — A controller may be described as a switching
device, usually with a movable arm or drum, that makes various
connections in a predetermined manner for the purpose of starting
one or more motors and regulating their speed, output or other
characteristics.

256 SWITCHING EQUIPMENT FOR POWER CONTROL

Functions. — Controllers are designed to be used with motors of
different kinds and to take care of the functions not incorporated
in the motor design in order to enable the latter to operate under
the specified conditions of load. The functions usually sup-
plied by the controllers are the following:

To limit the current during the acceleration of the motor.
To limit the torque during acceleration.
To change the direction of rotation of the motor.
To limit the load on the motor.
To disconnect the motor on failure of voltage.
To regulate the speed of rotation.

To start and stop the motor at fixed points, on the cycle of operation, or
at the limit of travel of the load.
To stop the motor.
To protect the operator from injury.

Not every controller has to embody all of these features in the
same degree but these are the underlying points of controller
design and they must be procurable when they are needed.

Faceplate Controller. — The simplest form of controller for
starting and regulating the speed of the D.C. motor is the face-
plate type shown diagrammatically in Fig. 163, and intended for
use with a variable speed motor connecting resistors in the arma-
ture and field circuit. With this type of controller the contacts
are mounted on the face of a suitable slab and a moving arm
makes the connections to the armature and field circuits, the
speed of the motor being changed by varying the field strength.
The rheostat arm is made in two parts, the under part making
contact with the segment of R-l to R-12 and with the contact
ring E, while the top arm engages the upper row of round contacts.
When starting, the two arms are held together by a latch. The
bottom arm is provided with a notched segment engaging
the plunger forming part of the low voltage release magnet. The
notch segment and pawl hold the arm in any operating position
after the low voltage magnet is energized. To start the motor the
contact arms are moved from the off position to contact R-l
and the connections can readily be traced from that point. The
arms are gradually moved to the right eliminating successively
each section of the armature resistor until the bottom arm makes
contact with R-12. In this position the armature is connected
directly across the lines and the segment E disconnected from
the rheostat arm. The shunt field circuit now is from the posi-

INDUSTRIAL CONTROL APPARATUS

257

live side of the line to the upper rheostat arm to the right hand
field contact F-12, thence to the field winding. This gives a
motor speed due to full field strength. If it is desired to increase
the speed of the motor the upper arm can be moved to the left
across the field contacts to insert resistance gradually in the shunt
field circuit, and thus, within its range, give the increased speed
desired, while the low voltage release magnet holds the lower

Armature Regulating
Beiiitor

Field Regulating
Eeiistor

L-

FIQ. 163. — Face plate controller.

arm on contact R-12. If the circuit is interrupted the low voltage
release magnet will allow the lower arm to be carried to the off
position by means of a spring. This in turn picks up the upper
arm and the two are moved quickly to the off position.

Drum Controller. — Another type of controller in common use
is the drum controller. These are used with machine tools for
varying the speed and reversing the direction of rotation of ad-
justable speed D.C. motors by means of armature and field
resistance. On the larger sizes magnetic blowouts are used. The
drum controller usually has two rows of contact fingers attached
to the frame work of the controller but insulated from it so as

258 SWITCHING EQUIPMENT FOR POWER CONTROL

to be electrically separated from each other. Between these
rows of fingers is mounted an insulated cylinder or drum which
is revolved by the handle. On this drum are mounted copper
segments of different lengths which engage the contact fingers.
The length and location of these segments are such as to make
different connections for each position of the controller handle.

Drum controllers are also used as master controllers with
contactors of various kinds to secure starting and speed regula-
tion of large A.C. and D.C. motors as well as the multiple unit
control of motor cars or locomotives on railway service. The
faceplate type of starter with field regulation for D.C. motors
may also be considered as a controller

Starting Resistance. — In starting direct-current motors it is
usually necessary to insert a resistance in the armature circuit
to limit the amount of starting current. As the motor speeds
up and its counter E.M.F. increases ,this starting resistance is
gradually cut out until, when the motor has reached full speed,
the resistance is all cut out and the motor armature is connected
to the full voltage of the source of supply. These starting rheo-
stats usually have various features; such as no voltage and over-
load release, sometimes combined with field control and making
the starters described in the next few paragraphs.

D.C. Starters. — The starters for use with constant speed D.C.
motors consist usually of a resistance to be inserted in the arma-
ture circuit to limit the amount of current taken when starting,
this resistance being gradually cut out by the movement of a
contact arm over a faceplate as the motor comes up to speed.
Such rheostats connect the motor field in circuit at the first
step and are provided with various safeguards such as low voltage
release, etc.

Low Voltage Release. — As a rule the low voltage release con-
sists of a coiled spring around the pivot of the rheostat arm for
returning it to the off position, and an electromagnet for retain-
ing the arm in the on position as long as the line voltage continues
above a predetermined minimum value. On failure of the line
voltage the magnet releases the arm which is at once returned
automatically to the off position by the spring.

To guard against drawing an arc when the contact arm leaves
the first contact in going to the off position, this contact is usually
protected by an arcing tip which provides a spring operated

INDUSTRIAL CONTROL APPARATUS

259

break, or a magnetic blowout is furnished that extinguishes
the arc that tends to form.

Typical D.C. Starter. — Fig. 164 shows the connections of a
typical D.C. starter with low voltage release. If the rheostat
arm is moved from the off position shown in the cut to the contact
R-I, current will flow from L plus to the arm; from this to contact
R-I through the regulating resistance to R-II; thence through
the armature and series field of the motor to L. The shunt field
is connected from R-I to L. Be.utor

As the rheostat arm is being
moved from R-I to R-II there
is a small drop in voltage
across the shunt field circuit
due to the field current flow-
ing through the starting re-
sistor, but this is so small that
it may be neglected and the
field can be considered as
having full voltage impressed
upon it. The rheostat arm is
provided with a spring which
returns it to the off position
and the handle is released L +
during the starting of the
motor. After the motor has
been brought up to speed and L ~
the rheostat arm rests upon

Contact R-II the low voltage Fl°- 164.— D.C. starter with low voltage

release.

release magnet holds the arm

in this position. Brush 'B' bridges between the terminals 'M'
and ' N ' so that in the running position the current passes from
L plus to terminal *M/ through the brush 'B' to the terminal
'N/ thence to the armature of the motor through the series
field to L-I.

Multiple Switch Starter.— With the larger D.C. motors where
the starting conditions are severe the face type of starter is not
found satisfactory, so recourse is had to multiple switch starters,
drum controllers, or contactors. Multiple switch starters
consist essentially of a number of switches mounted on a panel
and a separate resistance usually of cast-iron grids. The switches

260 SWITCHING EQUIPMENT FOR POWER CONTROL

are mechanically interlocked so that it is necessary to close them
in sequence.

Electrically Operated Starter. — In addition to the hand
operated starters, motor starters or controllers with electrically
operated switches or contactors are available for almost every
conceivable service. They can be arranged to start, stop or
reverse the motor manually at the will of the operator or auto-
matically at fixed limits and can be set to regulate and adjust
the speed. Arrangements can be made to have the motor auto-
matically perform a predetermined series of operations and the
control can be exercised from a point near the motor or from a
more distant point more convenient for the operator.

Starting Time. — In starting a motor a considerable amount of
energy is required to overcome the inertia of the motor and the
apparatus it is driving and a considerable amount of time is
required to bring the motor from a state of rest up to full speed.
To avoid wrecking the motor this energy must be admitted
gradually and resistance in the armature circuit is used for this
purpose. This resistance designed solely for starting purposes is
proportioned to carry the motor current only during the short
time necessary to bring the motor up to full speed. If the time
taken in starting is too long the resistance may be injured by
overheating while if too short the motor may be damaged or the
supply circuits seriously disturbed.

Push Button
Start St»p

FIG. 165. — Automatic acceleration with series relay.

Automatic Starting. — For these reasons a motor starter that will
automatically take care of the proper rate of acceleration presents
many advantages and such a starter can be devised by means of
contactor switches and suitable relays which are operated either
by the variation of the voltage drop across a resistance as the

INDUSTRIAL CONTROL APPARATUS

261

motor speeds up, or by the decrease in current which permits a
coil to drop its core as shown in Fig. 165, where acceleration is
controlled by a series relay. This is satisfactory where the volt-
age does not vary more than 12^ per cent, either way from a
constant value. Fig. 165 shows the connections of a shunt motor
controlled by means of two contactor switches, a push-button
switch, and a series relay. When the push button is closed in the
starting position, the coil of contactor No. 1 is energized, closing
the contactor and completing the circuit through the series
relay, the starting resistor, and the armature of the motor.
When the starting current has dropped to a certain value the
current in the series relay is no longer sufficient to hold open the
contacts so that connection is automatically made to the operat-
ing coil of contactor No. 2 closing that contactor and short-cir-
cuiting the starting resistors. With very large motors several
contactors with series relays are provided.

FIG. 166. — Automatic acceleration from counter E.M.F.

Counter E.M.F. — When a motor is started from rest and
accelerated to full speed, the voltage across the motor terminals
increases as the speed of the motor increases. If the coil of a
magnetic contactor is connected across the motor brushes the
current in this coil will increase as the speed of the motor in-
creases. Fig. 166 shows a starting arrangement based on the
counter E.M.F. method and it may be noted that the operating
coils of the three contactors have one side connected to the motor
brush farthest away from the starting resistor. The other sides
of the operating coils are connected to the taps on the starting
resistor, the coil on switch No. 1 being connected to R-2 on the
resistor. The voltage on this coil is equal to the line voltage
less the drop in voltage through the first section of the resistance.
As the speed of the motor increases the counter E.M.F. causes
decrease in the armature current. This reduces the drop to the
first section of the starting resistance. The voltage on the

262 SWITCHING EQUIPMENT FOR POWER CONTROL

Magnet Tcke
Magnet Core C]

Operating OoU /

Closing Contact!

operating coil of switch No. 1 is gradually increased until this
switch closes. Switch No. 2 has its operating coil connected to
R-3 on the starting resistor. The voltage on this coil is increased
by the closure of switch No. 1. The increase in current causes a
considerable drop in the second section of the starting resistance.
As this current gradually decreases due to the increased speed of
the motor, switch No. 2 closes. Switch No. 3 is connected
across the motor armature and closes when the counter E.M.F. of
the motor is nearly equal to the line voltage. The main contact-
ors for closing the main + and — circuits are not shown in the
diagram.

Series Lockout. — Another scheme of acceleration frequently
used is the series lockout method. With this arrangement the
magnetic contactor is provided
with a series coil and does not
require a separate relay for con-
trolling it. The closing of the
magnetic contactor depends upon
the saturation of the iron in one
portion of the magnetic circuit.
This can be understood from the
diagram of a contactor of this
design shown in Fig. 167. The
flux or magnetism in the iron is
caused by the current flowing
through the operating coil. This
flux passes through the air gaps in

the armature of the contactors. Part of this flux passes from
the armature through the armature brackets to the magnetic
yoke and thence to the magnet core. Another part of the
flux passes from the armature through the tailpiece of the
magnet yoke. The flux through this last circuit exerts a pull
which prevents the contactor from closing. The magnetic path
through the armature brackets is of small cross-section so that
when the current flowing through the operating coil exceeds a
certain value it becomes saturated and forces the balance of the
flux through the tailpiece holding the contactor open. As the
current decreases, the flux in the saturated armature bracket
remains constant and the flux through the tailpiece decreases
until it is not sufficient to hold the contactor open. The switch
can be adjusted to close at a predetermined value by changing the

FIG. 167. — Lockout contactor.

INDUSTRIAL CONTROL APPARATUS 263

hold out air gaps between the tailpiece and the magnet yoke
by means of a calibrating screw.

Lockout Contactor. — The success of starters with acceleration
control such as previously described, depends largely on the
contactors or contactor switches. Contactors are switches or
circuit breakers which are held in the closed position by some
auxiliary power such as a solenoid or compressed air. A typical
contactor is very similar to the lockout contactor shown in
Fig. 167, using a shunt coil instead of the series coil and omitting
the tail piece, the damping coil and similar features, so that as
soon as the shunt coil is energized the contactor is closed
against the pressure of a spring. Contactors are built both for
D.C. and A.C. operation and are made single pole and multi-
pole, single throw and double throw, in various capacities.
The main arcing contacts are usually protected by means of a
magnetic blowout.

These contactors are ordinarily used in connection with a
master switch or controller and protective relay switches of
various kinds to insure the performance of various functions,
such as the automatic cutting in and out of resistance in the sec-
ondary of an induction motor to maintain constant input to a
flywheel set or any similar feature that may be desired.

A.C. Starters. — Starters for A.C. motors may be divided into
two classes; those used with motors having a squirrel-cage or
short-circuited secondary and those for motors having a wound
secondary. In the former case the starting is done by impressing
on the primary a voltage sufficient to induce in the short-cir-
cuited secondary the current required to develop the proper
starting torque, and then transferring the primary connections to
full voltage.

Wound Rotor Motors. — With motors having a wound sec-
ondary it is customary to connect the primary to full voltage at
starting with the secondary short-circuited through a resistance.
As the motor speeds up this secondary resistance is cut out in one
or more steps until at full speed the secondary is short-circuited.

Squirrel-cage Motor. — With squirrel-cage motors up to about
7^-2 H.P. it is usually feasible to connect the primary immediately
to the full line voltage without drawing an abnormal current
from the line.

For textile work where small motors are used in large numbers
on circuits up to 550 volts, a special oil immersed switch is used,

264 SWITCHING EQUIPMENT FOR POWER CONTROL

this being made single throw for ordinary service, double throw
when reversing is wanted.

Auto Transformer Starting. — Under normal conditions the
most satisfactory means of obtaining the reduced voltage for
starting induction motors with squirrel-cage secondaries is by the
use of auto transformers, the connections for this method of
starting being shown diagrammatically in Fig. 168, the switching

Starting Connections

Running Connections

FIG. 168. — Auto-starter connections.

mechanism being omitted for the sake of simplicity. In the
starting position the voltage at the motor primary which is con-
nected to the auto transformer is cut down by the auto trans-
formers from 200 to 130 in this particular case. The current in
the motor primary is 200 amperes but the line current due to
the transformer action is only 130 amperes. In the running
position the motor primaries are connected directly across the
line and the auto transformers are disconnected at one end so
that their losses are eliminated.

Starting Voltage. — The starting voltage of induction motors
should not be greater than is required for the starting torque;
hence the starting voltage should be adjusted to the service
conditions. The auto transformers supplied for starting induc-
tion motors are provided with taps permitting the choice of any
one of several voltages. The auto transformers are designed
for starting service only and are not intended to be left perma-
nently in circuit.

Auto Starters. — The auto-starter switches or circuit breakers
are made of various types, usually either with wedge contacts
or brush contacts depending on the current to be handled. The
equivalent of the double-throw switch is usually furnished,
one throw energizing auto transformers and connecting the
motor to low voltage taps for starting and the second throw con-

INDUSTRIAL CONTROL APPARATUS 265

necting the motor directly to full voltage for running. The
second throw usually, though not always, completely disconnects
the auto transformers from the circuit.

Automatic Protection. — With auto starters this is usually
secured by means of overload trip coils, either connected directly
in the circuit or operated from current transformers. Usually
the overload protection is only in the running position. With
certain types of auto-starter switches the overload release device
consists of two solenoids with plungers in two different phases
and an oil filled dashpot on each solenoid plunger gives an inverse
time element feature. The switch contacts usually trip inde-
pendently of the handle so that the switch cannot be held closed
on an overload.

Automatic Starting. — By certain modifications these auto
starters can be made suitable for automatically starting and
stopping induction motors that are used for driving pumps or
compressors so that the level of liquids in reservoirs or the pres-
sures in a compressed air system can be maintained within
predetermined limits without supervision. The float type auto
starter is applicable to motor driven pumps that supply cisterns
and reservoirs, sumps, sewers, etc., if the pump is near enough so
that the rising and falling of a float in the reservoir or sump may
be communicated by rope drive to a weight device that operates
the auto starter.

With the pressure type regulator a pressure gauge switch and
relay are supplied that work in connection with an electromag-
netically operated valve, two cylinders and a spring and ratchet
device to move the auto-starter switch through the starting
position to the running position or return it to the off position.

Synchronous Motor. — Where self-starting synchronous motors
are used, they are provided with a squirrel-cage winding on the
rotor in addition to the usual field poles and field coils and, owing
to this squirrel-cage winding, they are started up as induction
motors and controlled by the same type of starting devices. Other
apparatus such as field rheostats and field switches are necessary
to take care of the motor when in the normal running condition.

Phase Wound Motor. — With induction motors having phase-
wound secondaries the method of control, as mentioned previ-
ously, is to connect the primary circuit directly to the high
voltage line with the secondary winding short-circuited through a
resistance which is cut out in one or more steps as the motor

266 SWITCHING EQUIPMENT FOR POWER CONTROL

comes up to speed. The switch or circuit breaker in the primary
circuit is made suitable for the voltage and capacity of the motor
while the secondary is taken care of by various devices such as
drum controllers, butt contact switches, contactors, etc.

Mill Work. — For reversing mill or hoisting work using induc-
tion motors with wound secondaries, many very ingenious and
highly satisfactory installations have been put in service using
solenoid operated magnet switches or contactors for the secon-
dary and occasionally for the primary circuits. These are worked
from a master controller or similar device or are operated auto-
matically by the positions of the rolls, hoist, etc. Automatic
acceleration can be obtained in the same manner as indicated on
Figs. 165 and 166, and various safeguards such as dynamic brak-
ing can be employed.

Flywheel Sets. — Another application for contactor control
with automatic features is with flywheel motor-generator sets
using a very heavy flywheel in connection with a D.C. generator
and an A.C. motor with wound secondary. The power put
into the flywheel or delivered up by it depends on the variation in
speed of the motor generator and by varying the resistance in the
motor secondary this speed regulation can be secured. By the
use of relays similar to those described, the input to the motor and
consequently the load on the A.C. system can be kept practically
constant while the output of the D.C. generator supplying power
to a D.C. hoist or rolling mill motor is undergoing wide fluctua-
tions, the energy in the flywheel taking care of the difference
between the constant input and the variable output.

Automatic Substations. — An application of contactor control
of rapidly increasing importance is the automatic substation by
means of which rotary converters, motor generators, or other
transforming devices are cut into and out of service automatically
with the varying demands on the system. Descriptions of
these automatic substations are given later.

CHAPTER XI
SWITCHBOARDS— GENERAL INFORMATION

In taking up the question of switchboards, after having de-
voted many pages of this book to a consideration of the apparatus
for power plant control, it should be noted that the term switch-
board as here used is applied to the collection of panels, pedestals,
posts, control desks, etc., on which are mounted the instruments,
relays, switches, circuit breakers, etc. so that from this point of
view the switchboard is practically a collection of switching
apparatus assembled in a logical manner to facilitate the control
of various electrical circuits.

Diagram. — The apparatus previously described can be com-
bined in various ways to secure the results desired in power
plant control. These various combinations are usually expressed
in the form of a diagram of connections before any attempt is
made to decide on the switching equipment.

D.C. Connections. — For direct-current service the main con-
nections usually embody a knife switch and fuses or carbon cir-
cuit breakers for securing the automatic protection. In most
cases, only a single set of bus bars is employed, and the connec-
tions are very simple.

A.C. Connections. — For alternating-current service the con-
nections are usually more complicated, and as the plants are
larger and more important, greater flexibility is usually provided.

In making up a preliminary diagram it is usual to show all of
the circuits whether direct current, single phase, or polyphase
by means of a single line per circuit and to indicate oil circuit
breakers, disconnecting switches and similar devices by simple
conventional signs.

Single Line Diagram. — In these single line diagrams it is
seldom necessary to show the metering and relaying equipment,
and usually the diagram is reduced to its simplest elements,
merely locating the main generators, transformers, feeders, oil
circuit breakers, disconnecting switches, and bus bars.

267

268 SWITCHING EQUIPMENT FOR POWER CONTROL

Typical Connections. — Fig. 169 shows a number of typical
connections between generator and bus circuits. On this dia-
gram the generators are represented by large circles, the oil
circuit breakers by rectangles, the disconnecting switches by
two small circles, transformers by two saw tooth lines, and out-
going feeders by an arrow head. While the main connections
are fairly evident from the diagram, the following notes point
out some of the principal features.

Fig. 'A' shows a single-bus system with a generator feed-
ing through an oil breaker and a disconnecting switch to a bus;
this being about the simplest possible arrangement although oc-
casionally the disconnects are omitted.

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FIG. 169. — Typical connections of generators and bus.

'B' shows a double-bus system with a main breaker, two
selector breakers and disconnects for isolating the selector
breakers from the two sets of busses. With this arrangement
there are two breakers in series between any generator or bus
or any feeder or bus, this permitting the testing out of each
breaker independently before tying in the circuit. This scheme
was a favorite one in the early days of oil circuit-breaker develop-
ment when complete reliance was not placed on the satisfactory
performance of oil breakers. The disconnects permit isolating
either selector breaker from the bus, but owing to the absence
of any disconnecting switches between the main breaker and the
selectors, it is necessary to shut down a circuit before any work
can be done on any of the oil breakers.

'E' shows a similar arrangement with the addition of dis-
connects on each side of the selector breakers as well as discon-

SWITCHBOARDS— GENERAL INFORMATION 269

nects between the generator breaker and the common connection
to the two selectors. With this arrangement either of the selector
breakers can be completely isolated by means of their disconnects
without shutting down the generator or feeder or shutting down
the bus. The disconnects between the common connection and
the generator breaker are utilized for isolating the generator
breaker in case the selectors are to be used for tying together the
two sets of busses.

' D ' shows a somewhat simpler arrangement with two sets
of busses and two selector breakers omitting any main generator
breaker. This is a very common arrangement where two sets of
busses are desired.

' C ' shows a generator with a generator breaker and a certain
number of disconnects so arranged that the generator can be
connected either to the bus or to the low tension side of a trans-
former bank or the low tension side of a transformer bank can
be connected to the bus, while the generator is shut down.

'F' shows a modification of this arrangement with the genera-
tor tied in solidly on the low tension side of its step up transformer
with a breaker and disconnects on the high side of the trans-
former, breaker and disconnects for connecting the machine
to the station auxiliary bus.

*G' shows an arrangement very similar to 'C,' but with an
additional oil breaker to facilitate connecting the generator to
the main bus.

' H ' shows an arrangement of a generator with one oil breaker
and two sets of disconnects for connecting the machine to either
of two sets of busses.

'I' shows two generators feeding through breakers and dis-
connects to a generator bus. This generator bus in turn connects
through breaker and disconnects to the main bus, or through
another breaker and disconnects to the low tension side of a trans-
former bank. With this arrangement the two generators are
considered essentially as a single unit and are arranged for feed-
ing their own transformer bank, or tieing to a main bus bar.

'J' is essentially the same arrangement as 'D' except that
one bus is considered as the main bus, and the other as a trans-
fer bus for emergency purposes.

'K' shows a combination of one generator and one trans-
former bank with a total of three breakers and suitable discon-
nects so that the generator may be connected directly to its own

270 SWITCHING EQUIPMENT FOR POWER CONTROL

transformer bank or the generator or transformer connected to
the transfer bus. A slight modification of this scheme, using
the same number of breakers, has one breaker connecting the
generator directly to the transformer; a second breaker connect-
ing the generator to the bus, and the third breaker connecting the
transformer to the bus, so there are always two paths between
the generator and transformers.

'L' shows an arrangement of main bus, selector bus, feeder
group busses, etc.

The remaining schemes 'M' to 'U' inclusive, are slightly
more complicated, but are all based on the main connections
used in actual plants. As practically all of the connections indi-
cated in Fig. 169, can be utilized either for generator or for feeder
circuits, they may be considered as forming the elements of dia-
gram construction, and most of the more complicated diagrams
are combinations of the various methods indicated.

Instrument Transformers. — After completing the elementary
single line diagram, it is frequently a good plan to locate the
current and the potential transformers needed for the operation
of instruments and relays, and then to prepare a detail diagram
showing the interconnections of these various features.

T i r^ri i i i i r

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FIG. 170. — Diagram of single bus system.

Single Bus. — For simple plants where economy is of prime
importance, the straight single-bus system as indicated in Fig.
170, is usually adopted. This diagram shows 3 generators and
six outgoing feeders, each circuit being provided with an oil
circuit breaker and a disconnecting switch, and the current
transformers being located in such a position as to carry the com-
bined output of all the generators. With a single-bus system
such as shown, bus bar trouble, which is very infrequent, necessi-
tates complete shut-down. To replace the oil, inspect or adjust
any circuit breaker, it is necessary to shut down the particular
circuit involved, but it is not necessary to shut down the entire
plant, as disconnecting switches are provided for isolating the
breaker from the bus. A still cheaper and simpler arrangement

SWITCHBOARDS— GENERAL INFORMATION 271

adopted for small boards, dispenses with the disconnects, but
this makes it necessary not only to shut down a particular cir-
cuit, but also the entire plant, unless the voltage is so low that the
repair man is willing to risk working on the breaker while the bus
is alive.

Double Bus. — By adopting a double-bus system of one breaker
and two disconnects per circuit, one bus can be shut down for
inspection of the board or insulators without shutting down any
circuit by opening all of the disconnects tied on to that bus. If
any particular feeder is giving trouble due to grounds or frequent
short circuit, it may be connected to one bus with one generator,
and the rest of the plant connected to the other bus. By using

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FIG. 171. — Diagram of double bus system.

the double-bus system, with two breakers per circuit, any breaker
can be cut out of service for inspection or repair without shutting
down a circuit or without shutting down either bus provided
suitable disconnects are employed. A bus can also be shut down
at any time to have insulators cleaned or connections altered.
A typical arrangement employing the double-bus, double cir-
cuit-breaker system is shown in Fig. 171, this showing two gene-
rators, three outgoing feeders and a bus tie breaker. In many
systems employing the double-bus and double circuit-breaker
equipment, the breakers are interlocked so that normally a cir-
cuit can only be connected to one bus at a time. The tie breaker
is used for connecting the two busses together, and provision is
made for synchronizing around the tie breaker. In any case,
however, where it is desirable to be able to transfer a generator
or feeder from one bus to the other without opening the circuit,
the breakers are not interlocked. In this case, the tie breaker
is dispensed with and when it is desired to tie the two busses
together, two of the generator breakers or feeder breakers are
connected in at the same time.

Ring Bus. — Where stations of moderate size require great
flexibility and maximum security and where due to the low vol-

272 SWITCHING EQUIPMENT FOR POWER CONTROL

tage employed, the current in the bus is apt to be excessive unless
limited to the full output of one machine, the arrangement shown
in Fig. 172 is adopted. With this arrangement, each generator
and feeder is provided with a breaker and the equivalent of double
throw disconnects. The busses are practically divided into four
sections which sections can be tied together to form a complete
ring bus.

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FIG. 172. — Diagram of ring bus system.

O Q LJ LJ LJ O

FIG. 173. — Diagram of typical plant with sectioned bus.

Sectioned Bus. — Fig. 173 shows a plant controlling four
generators, four step-up transformer banks and two outgoing
lines using the single sectionalized bus system. Each circuit is
provided with one breaker and one set of disconnects, but the
busses are so sectionalized, that normally each generator will
tie in with its own transformer bank, and two transformer banks
will normally supply current to their own outgoing line circuits.
The low tension bus is so sectionalized by means of disconnecting
switches that the local feeders may be fed from either half of the

SWITCHBOARDS— GENERAL INFORMATION

273

station. A modification of this system utilizing the same number
of low tension disconnects, utilizes the four sets of disconnects,
shown for sectionalizing the low tension bus, for tying the com-
bined generator and transformer bus to a low tension transfer
bus, which low tension transfer bus supplies the current to the
local feeders.

Special Bus. — Fig. 174 shows the general scheme of connections
adopted for the original plant of the Rio Janeiro Tramways Light
& Power Company controlling six generators, six banks of step-up

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FIG. 174. — Diagram of connections for Rio de Janeiro.

transformers and four outgoing transmission lines. The plant is
normally operated with each generator connected to the low
tension side of its own transformer bank. Suitable breakers and
disconnects are provided however, so that any generator may be
connected to the low tension bus by a second oil breaker or the
transformer bank may be connected to the low tension bus by dis-
connecting switches. The low tension bus is sectioned in the
middle by means of breaker with disconnects, and the low ten-
sion feeder bus can be supplied from either half of the main low
tension bus through proper disconnects. This feeder bus with

274 SWITCHING EQUIPMENT FOR POWER CONTROL

auto transformers is arranged for furnishing current to the ex-
citer motors.

On the high tension side each transformer bank is provided
with a breaker and double-throw disconnects connecting to
either of two high tension busses; these high tension busses are
each split in the middle by means of section breakers and are
tied together through tie breakers. The four outgoing lines
are each provided with two sets of disconnects for connecting to
either of the two sets of busses and an oil breaker. As the
double-throw disconnects on the high tension side are of the
selector type, any circuit can be connected to two busses at
the same time, so that when it is desired to transfer a transformer
or line circuit from one bus to the other this can readily be done
and the work is facilitated by the use of the tie breakers so that
no current will ever have to be opened on the disconnecting
switches.

Flexibility. — Different engineers have their own ideas as to the
amount of flexibility necessary or advisable in any particular
plant, and the system adopted is frequently a compromise so as
to secure a reasonable amount of flexibility with the minimum
amount of switching equipment.

For the simpler plants using direct-control, panel mounted,
devices, usually the single-throw system is adopted. For some-
what larger plants utilizing distant mechanical control oil circuit
breakers, the single-bus or double-bus system can be used and
normally sufficient space can be made available for the location
of one or more sets of bus bars and suitable disconnecting
switches.

For the largest plants using electrically operated breakers,
practically unlimited choice is available as to the schemes of
connections to be employed.

In the descriptions that follow of switchboard panels, some of
these features of main connections are considered more fully,
while the more complicated systems utilizing distant control
devices are considered in connection with structures and station
layout arrangement.

Largest Builders. — The main differences in the switchboards
built by different manufacturers lie in the apparatus mounted on
the panels and where the switchboard builder is also a manu-
facturer of instruments, switches, breakers, etc., he naturally
prefers to use his own equipment. The two largest electrical

SWITCHBOARDS— GENERAL INFORMATION 275

manufacturers in the United States that build generators, trans-
formers, synchronous converters and other power plant equip-
ment are the General Electric Company and the Westinghouse
Electric & Manufacturing Company, and the two of them together
do the largest portion of the switchboard business in the United
States, usually arranging to furnish the switching equipment for
the control of their own machines, although this is not always
the case.

The general features of switchboard design of the two com-
panies in question have naturally been the result of their
apparatus development and the competition for switchboard
business has led to the desire for standardization to bring down
manufacturing costs and to expedite production.

Other Builders. — There are of course a number of other switch-
board builders competing for the switchboard business, particu-
larly for the direct-current light and power work where there are
many more different builders of generators than there are in A.C.
work. The D.C. light and power switchboards for large office
buildings are usually made according to specifications of an
architect or engineer and usually do not conform to any particular
standard of construction. For this class of switchboard work,
the independent contractor and the small builder is often in a
better position to carry out the architect's ideas than a large
manufacturing company whose shop routine is designed especi-
ally for quantity production of standard equipment.

Treatment. — In treating the question of switchboards the
general features will be taken up first, then the simpler D.C.
boards, then the more complicated ones, these in turn being
followed by the A.C. boards that are usually more involved and
frequently affect the station design very materially. While the
illustrations may seem to show the equipment of one builder
more often than that of others, this does not imply any idea that
it represents the actual relative proportion in which the various
types are used in actual practice, but merely that the author
found it simpler to utilize the illustrations that were easiest to
obtain.

Differences. — In the usual illustration of a switchboard it
takes an expert to distinguish what type of carbon breaker or
knife switch is shown. Where oil circuit breakers are used the
cover plates of different designs are more or less a distinguishing
feature, and whether the meters are shown as rectangular or

276 SWITCHING EQUIPMENT FOR POWER CONTROL

circular is often a clue to the builder of an A.C. switchboard,
but comparatively few changes would be necessary to alter the ap-
pearance of the usual switchboard so that it would be difficult
to tell what maker was responsible for it.

Standards. — As a result of the standardizing process the general
practice of many switchboard makers is becoming more and more
similar and one of the main ideas of the first part of this chapter
will be to point out the gradual evolution of this standard practice
and to give the reasons for various features. These reasons of
course apply broadly to all switchboards both of the direct-control
and the distant-control types. However, the former applying
to moderate capacity plants followed "standard practice"
more closely than the latter due to the many special features in
large plants.

The earliest so-called panel boards were made of wooden panels
with the various switches, instruments, etc., each on its own
base and attached to the wooden panel with the wiring either on
the front or the rear.

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mmmm

FIG. 175. — Wooden switchboard for Korea built 1887.

Wooden Board. — Fig. 175 shows a board of this type,
built about 1887 for Korea and used for the control of
four direct-current low voltage generators and eight feeder
circuits. Each generator was provided with a pilot lamp, an
ammeter, a single-pole carbon break circuit breaker, a 2-pole
switch and a rheostat. Each of the eight feeder circuits had a

SWITCHBOARDS— GENERAL INFORMATION

277

2-pole switch and a voltmeter was furnished with a voltmeter
switch for connecting it to various circuits. The switchboard
was made of tongued and grooved lumber with all of the wiring
on the back and was strictly up to date at the time. of its manu-
facture.

The next step in advance was the elimination of the wooden
panel or framework. Each piece of apparatus was then mounted
on a marble slab and was arranged for placing in an angle iron
frame work and switchboards were made by combining the
necessary ammeters, voltmeters, switches and rheostat slabs
to make the panels for the different generators, feeders, etc.

FIG. 176. — Panel Switchboard Brush Electric Co. of Baltimore 1894.

Old Panel Board. — Fig. 176 shows a large double-deck board
of this design supplied to the Brush Electric Company of Balti-
more about 1894 and used for the control of A.C. and D.C.
generators and feeders. The five panels to the left on the
lower floor were used for the control of five 1000 K.V.A. 2-phase
A.C. generators operating independently, those being practically
two single-phase machines with their armatures coupled together
mechanically and displaced through an angle corresponding to
90 electrical degrees. Each panel had a pilot lamp, two am-
meters, two voltmeters, two 2-pole double-throw switches, two

278 SWITCHING EQUIPMENT FOR POWER CONTROL

sets of field plugs and two rheostat faceplates for the two sepa-
rate field circuits used with the 2-phase machines. The next
two panels with the bell and clock were station panels, the next
four exciter panels, and the last two D.C. feeder panels. The
balcony was devoted to A.C. feeder circuits each panel control-
ling a single-phase feeder which could be transferred by means of
plugs and cables and a 2-pole, double-throw switch from any
one of eight single-phase bus bars to any other bus.

This form of construction was entirely fireproof but various
disadvantages ultimately led to its being superseded by the
modern design of panel switchboards with the apparatus grouped
on panels made of one or more comparatively large pieces of
marble or slate.

Present Standards. — These lines of switchboards manufac-
tured by various companies are the result of careful study of

requirements. In general, the
standard switchboards may be
divided into two types with re-
gard to their framework. The
cheaper and smaller panels are
mounted on a framework of gas
pipe and usually comprise panels
about 4 feet 0 inches high with
a space below them. The larger
and more expensive panels have
a total height of about 7 feet 6
inches running down to the floor
and are provided with an angle
iron or pipe frame. For the
small boards the frame is as
shown in Fig. 177 made of verti-
cal gas pipe one at each end of
the board and one at the junc-
tion line of adjacent panels.

Special fittings are supplied for clamping to the pipe and a
continuous flat strap 3^ inch X 1% inch in section running
the length of the board is bolted to the fittings at the
top of the pipe to stiffen the framework and to provide a suit-
able location for attaching wall braces, transformers, wiring,
brackets, etc. The lower end of the vertical pipes are screwed
into ornamental cast-iron bases which can be bolted to the floor.

FIG. 177. — Pipe framework for
switchboards.

small

SWITCHBOARDS— GENERAL INFORMATION

279

These bases are circular and can be screwed on or off a short
distance to allow for slight irregularities in the floor. Special
fittings are designed for clamping to the upright pipes and the
panels are bolted to these fittings. The entire design of this
frame work has been made with the view of minimizing the
amount of machine work and expediting the assembling of the
frame. For small boards this type of frame has proved to be
very satisfactory and a complete line of brackets to support bus
bars, transformers, fuse blocks, regulators, etc., is available.

Pipe Frame. — While the gas pipe construction is considerably
lighter than the angle iron construction it has been found amply
secure for these smaller switchboards and in fact some manu-
factures use gas pipe construction for most of their larger switch-
board installations. Where the
number of panels does not exceed
four or five the complete board
can sometimes be shipped with
the panels attached to the frame-
work and most of the small wiring,
etc., undisturbed but if the board is
a large one the panels and frame
are shipped separately

Angle Frame. — For the larger and
more expensive panels a framework
of angle iron construction, Fig. 178,
is used by certain builders. Each
panel of a total height of 90 inches
is provided with two 2 X 3 X
24-inch angle irons or some similar
section with the 2-inch side next
the panel and these angle irons
extend from the bottom of the panel
to within ^ inch of the top. The

vertical angles on adjacent panels are bolted together through
the 3-inch web and are provided with corner angles for bolting
at the bottom to a 6 X 2-inch channel iron forming the base of
the frame and at the top to a ^ X 1%-inch flat iron. The chan-
nel iron and the top iron are made continuous and the entire
length of the board provided same is not over 16 feet. Where
the length exceeds this amount the frame is divided at the
junction line of two panels. This arrangement makes a very

;«

"T<

*s- „ „

„ *

J>»'G
^"''l

Angl. Iio^*

-; — *- 1

^art

^ -4

r2" *4

4^" -Hr-

FIG. 178. — Angle framework
large switchboards.

for

280 SWITCHING EQUIPMENT FOR POWER CONTROL

stiff construction and the channel iron base makes up for any
irregularities in the floor and distributes the weight better than
a framework, where no channel iron base is furnished. The top
provides a means of attaching wall braces, brackets, etc. Some-
times a flat soleplate or wooden sill is provided in place of the
channel iron base or the vertical angles are connected directly
to the floor.

Shipment. — Each panel is shipped bolted to the two angle
irons that form its individual frame and this obviates any neces-
sity of disconnecting the wiring between the various slabs mak-
ing up the panel. The framework being shipped with the panels
to a large extent reduces the breakage due to rough handling and
facilitates the erection of the board at its destination. With a
pipe framework the panels and uprights must be shipped sepa-
rately, unless a temporary upright is furnished for each panel
but one.

Material. — After trying various materials practically all
switchboard builders have come to the use of either slate or
marble although in a few instances soapstone, brick or steel has
been used but these cases are so few that they can be left out
of consideration.

Marble. — Marble used on switchboards is usually of the grade
known as "Blue Vermont," although occasionally "White Ital-
ian" or "Pink Tennessee" is used. This is ordinarily beveled
with a 45-degree bevel of either % inch or ^ inch measured in the
plane of the front of the panel or its edge and not along the bevel.
The marble is sometimes polished on the front face and bevels
and occasionally the edges and back. Sometimes the marble or
slate is given a polished black enamel finish but the present
standard is a dull black marine finish applied to honed panels of
marble or slate of any color or an oil finish applied to natural
black slate.

Blue Vermont. — The name "Blue Vermont Marble" was ori-
ginally applied to the marble of gray or bluish tint obtained from
the quarries of the Proctor Blue Vermont Marble Company who
supplied most of this grade of marble, but other quarries supply
marble of practically the same kind. Polished blue Vermont
marble in the opinion of many people presents a somewhat finer
appearance than any other material available for switchboards
but it has the drawback of showing oil stains and scratches and
it is hard to secure a good match of shade and grainings for large

SWITCHBOARDS— GENERAL INFORMATION 281

switchboards. The difficulty of keeping an exact record of the
shades and markings of the marble shipped to a certain customer
who desires additions to his board militates somewhat against
its use. The same remarks apply to English vein, white Italian
or pink Tennessee marble.

Slate. — Ordinary slate owing to its irregular color and marking
is seldom used in its natural state but is usually given an enamel
or marine finish, while natural black slate is given an oil finish.
Slate can be given a baked enamel finish of glossy black and
with this finish oil has little effect and there is no difficulty in
securing a good match. This finish is somewhat more expen-
sive than the polished and has the same drawback of showing
scratches, etc., which cannot well be removed or covered over
without re-enameling. As this involves taking the panel from
the board, removing all apparatus and baking the panel, this is
seldom done. When a black enamel finish is given to marble
trouble is apt to come from the marble crumbling during the
baking process.

Marine Finish. — This finish as applied to panels of either slate
or marble consists of a dead black paint, usually applied with an
atomizer to a honed finished panel. This finish is cheap, very
attractive, does not show oil stains, and if the panel is scratched
a little, fresh paint will make it look as good as new. The dull
black finish moreover, causes the instruments, switches, etc.,
to stand out in bold relief and has no tendency to reflect the
light in the eyes of the attendant while polished or enameled
panels have this tendency.

Oil Finish. — When natural black slate is used it is given an oil
finish with vaseline or some similar material and it has practi-
cally the same advantages as the marine finish.

Slate vs. Marble. — Where switchboard panels are to be given
a black finish the question of whether slate or marble should be
used is largely a question of cost of insulation. Slate is con-
siderably cheaper and somewhat stronger than marble and where
the voltage of live metal parts mounted on the panels does not
exceed 750 volts it answers just as well. This makes it suitable
for all boards except those having ground detector receptacles,
fuse blocks or similar apparatus mounted on the material of the
panel and connected to a circuit of 1200 volts or more.

Small Panels. — The smaller and cheaper panels intended for
use with gas pipe framework are made in single slabs and as a

282 SWITCHING EQUIPMENT FOR POWER CONTROL

rule have a height of 48 inches and a width of 16 to 24 inches al-
though some of the panels are smaller. In order to secure suffi-
cient mechanical strength to stand the jar of oil circuit breaker
opening, the panels are made of 13^ -inch thick material for
alternating-current service and panels with this thickness of
1^2 inches have been usually adopted as standard.

Bevels. — A bevel is furnished on all of these panels to improve
their appearance and also because it is almost impossible to
secure marble or slate with a square edge that will stand hand-
ling. It has, in fact, been found advisable to use a small bevel
or rounding of ^{Q inch or % inch on the back of the panel to
prevent chipping off.

Early Panels. — When the building of small panel boards
for A.C. and D.C. work was begun it was found by one large
manufacturer that a height of 48 inches with a width of 32
inches for the A.C. panels and 22 inches for the D.C. panels
was the minimum size that would permit the mounting of all
of the then standard apparatus required with due regard to
insulation distances and the lining up of apparatus on generator
and feeder panels of various capacities and these particular sizes
have been retained as standard.

Frame.— - Where the standard frame is used with panels 48
inches high the bottom of the panel is 28% inches from the floor
and there is sufficient clearance to allow a sub-panel to be used.
The height selected for the frame brings the meters in line with
the operator's eyes and places the switches, rheostats, etc., in a
convenient location. For the heavier lines of panels, 2-inch mar-
ble or slate has been adopted as standard for mechanical reasons.
This thickness is required for the heavy switches, circuit breakers,
etc., often furnished on these switchboards. These 2-inch panels
are all provided with a %-inch or ^-inch bevel on each front edge.
With three division panels employing slate, the thickness is fre-
quently reduced to 1% inches.

Westinghouse Panel Sections. — The total height of standard
switchboard panels of one design, viz., 90 inches from the channel
iron as well as the division resulting in having a 25-inch lower
slab on Westinghouse boards, is due to the fact that these
particular dimensions were best adapted to the line of switches,
circuit breakers, meters, etc., which were in use at the time when
the standard railway switchboard panels shown in Fig. 179 were
first brought out. The lower 25-inch slab was used for the rheo-

SWITCHBOARDS— GENERAL INFORM A TION

283

stat faceplates having the contacts and contact mechanism on
the rear and the hand wheels on the front of the panel. In order
to correspond with the old D.C. panels, the A.C. panels were
brought out having a main slab 65 inches high.

Fio. 179. — Old style Westinghouse two section switchboard.

G. E. Panel Sections. — While the Westinghouse Company was
bringing out 65-inch X 25-inch panels, the General Electric
Company working along their own lines and designing panels
suitable for their apparatus, arrived at the same total height, but
divided their panels into 2 slabs 62-28 inches high with a %-inch
bevel. This question of bevels and division of the panels is
almost entirely a question of appearance.

Three Section Panels. — When the present standard laminated
brush type carbon break circuit breaker was designed, it was
found advisable to mount this breaker at the top of the panel in
order to take advantage of the tendency of an arc to rise and to
avoid placing apparatus above the arc. As all of the Westing-
house standard breakers up to 3000-amperes capacity required a
space of something less than 20 inches, they soon decided to divide
the main upper 65-inch panel into 2 slabs, one portion being 20
inches high to contain the circuit breaker, the other portion 45
inches high to contain the meters, switches, etc. By placing the
circuit breaker on a separate slab, the calibration of the breaker
was greatly facilitated. For this reason, the standard D.C.
panels of the Westinghouse Electric & Manufacturing Company
both for railway work and for light and power work were divided

284 SWITCHING EQUIPMENT FOR POWER CONTROL

into 3 slabs, upper 20 inches high, the middle 45 inches, and the
lower 25 inches, Fig. 180. With the growth in the capacity of
synchronous converters, larger breakers than 3000 amperes became
necessary, and these, while too long for 20-inch slabs, would go on
25-inch slabs so the latest Westinghouse panel division is 25 inches,
45 inches, 20 inches, and the G. E. division is 31 inches, 31 inches,

FIG. 180. — Westinghouse three section railway switchboard.

and 28 inches, Fig. 181. Nearly all switchboard builders are
now following this practice of putting heavy circuit-breakers on
separate slabs. Instruments are frequently placed below the
circuit breakers on the 31-inch upper sections of G.E. panels.

Direct Control. — Direct-control switch gear is used with practi-
cally all direct-current plants and most of the smaller alternating
ones and the main switching appliances are located directly on
the switchboard which is usually of the panel type. Such boards
are familiar sights in moderate size plants.

SWITCHBOARDS— GENERAL INFORMATION

285

Many Builders. — Owing to the comparative simplicity of
direct-control switchboards particularly for low voltage direct-
current service the number of builders of this type of board is
very large and the consequent competition has aided greatly in
bringing about cheap and simple apparatus for this class of
service. In order to meet close competition in the matter of
cost and promptness of delivery nearly all switchboard builders
have come to the practice of using so-called "standard panels"
wherever possible and very complete "lines" of standard panels

31-

-28'

•31

\4-~20 -— - -S

|< ~—45 ->

< 25"- ->j

flp

FIG. 181. — Three section panel.

have been designed to take care of all ordinary and some extra-
ordinary features that are apt to be met with in plants of moderate
capacity that can be satisfactorily handled by "direct-control
switch gear."

Switchboards can be obtained to meet any possible require-
ment that may arise in the control and application of electrical
power.

Standard Panels. — These have been designed using standard
apparatus for various classes of services and these panels will be
found to meet practically all ordinary requirements that may
come up in switchboard installations.

Specials. — However, for special conditions that cannot be met
by these standard panels, or where special material is desired,

286 SWITCHING EQUIPMENT FOR POWER CONTROL

the extensive manufacturing facilities and long engineering
experience of the companies insure that such propositions will
be taken care of promptly and completely.

Requirements. — The selection of suitable switchboard ap-
paratus for certain requirements is naturally governed by several
conditions. In some cases first cost is the determining feature.
In most cases continuity of service is of considerable importance.
In many cases continuity of service must be provided regardless
of cost. In all cases, the maximum degree of safety to life and
property that can be obtained should be the goal. These, and
other considerations, such as space available, voltage and capa-
city of plant, govern the proper selection of a switchboard equip-
ment.

With regard to the kind of current controlled, switchboards
are naturally divided into two broad classes: Direct-current
switchboards and alternating- current switchboards.

D.C. Boards. — The direct-current switchboards cover a wide
field and include in their range every application of direct current.
In general, the direct-current panels may be divided into two
classes — those of the larger capacities, and those of the smaller.

The larger boards are used for direct current railway systems
and for lighting and power systems of large industrial plants,
hotels, central stations, etc. The smaller generator and feeder
panels are intended primarily for light and power systems of
small industrial plants, small hotels and central stations of small
capacity, etc., while the battery-charging panels are designed
for controlling the charging of storage batteries used in lighting
service and on electric vehicles.

A.C. Boards. — Alternating-current switchboards may be di-
vided into the following three distinct classes, depending on
the mounting and method of operation of the apparatus:

1. Direct-control boards, or those in which all apparatus is
mounted on the panels or on their supporting framework.

2. Manual remote-control boards, or those with manually
operated circuit breakers mounted apart from the board and
operated by means of handles on the panels.

3. Electrical remote-control boards, or those with electri-
cally operated circuit breakers mounted apart from the board
and operated by means of control switches mounted on the
panels.

Class of Board. — The particular class of board to be selected

SWITCHBOARDS— GENERAL INFORMATION 287

for any installation will depend on a number of considerations.
For instance, the capacity of the station, the desired operating
features, the allowable space, the permissible cost — all are factors
in the selection of the proper type of board.

Limitations. — The capacity of a station determines the class
of switching devices that can be used, and this in turn usually
determines the class of switchboard to be installed. The desired
operating features are a factor in the selection of either me-
chanically or electrically controlled apparatus. The allowable
space may determine the type of equipment. The direct-control
switchboard occupies less total space than any other, but some-
times involves more valuable space in the operating room than
the remote-control, hence the disposition of the available space
sometimes must be considered. With regard to cost, the direct-
control board usually costs less than any other, although the
saving in main cables, may sometimes be great enough with the
remote-control boards to reduce the total cost of cables and
switchboard to that of the direct-control, or to even less.

Direct Control. — The limitations in the use of the direct-con-
trol switchboards are chiefly electrical. Experience has demon-
strated that there are certain limits of capacity above which oil
circuit breakers should not be mounted directly on the panels.
The reason for this limitation lies chiefly in the danger to at-
tendants from high voltage apparatus when in close proximity
to low voltage control and instrument wiring, rheostats, etc.,
which require inspection and occasional repairs, or from mechani-
cal reasons resulting from the size and amount of copper busses
and risers when the current involved exceeds certain amounts.

Remote Control. — Manual remote-control switchboards are
limited in their application by the physical, rather than the elec-
trical, characteristics. They are applicable where the simplicity
of connections or accessibility desired cannot be obtained with
panel mounted apparatus, where station capacity or voltage is.
so high as to make it desirable to mount oil circuit breakers apart
from the panels, and where station arrangement permits the use of
manually operated remote controlled oil circuit breakers.

Electrical Control. — The electrical control switchboard usually
takes one of three general forms, namely : the panel board, the
combination control desk and elevated instrument board, or
the combination pedestal and instrument post board. All
of these are detailed later.

288 SWITCHING EQUIPMENT FOR POWER CONTROL

Panels. — As in the application of the other types of boards
there is no well denned field to which any of the three forms is
confined. However, the panel board is frequently chosen for
plants of moderate capacity, and, occasionally, for those of high
capacity where the number of circuits are few and the length of
the board is, kept therefore within a space which may be covered
almost instantly by the operator. The panel board is usually
chosen for substations, as it must generally harmonize with, and
may be an addition to, the panel board controlling the direct-
current and low tension alternating-current circuits.

Desks. — The combination control desk and elevated instru-
ment board can be used for stations of any capacity and any
number of circuits. The particular form chosen, however, must
depend upon local conditions, but in general, for a small number
of circuits, the linear desk is employed, while for a greater
number of circuits, the semi-circular desk is most desirable as it
permits a uniform view of all sections of the desk from one
central position.

Pedestals. — When a station is equipped with very large units,
pedestals for the control switches and receptacles, with posts for
supporting the instruments, are sometimes used because of the
complete individuality thus obtained for each unit.

On remote-control boards all busses and connections are shipped
in bulk uncut. On panel mounted boards, if bus bars and con-
nections are of strap, rod, or tubing, they are cut, bent and put in
place; if they are of solid insulated wire they are shipped in reels,
uncut, together with the wire for control and instrument busses
and for primary leads of voltage transformers.

Panel Sequence. — The sequence of panels is important on
account of the necessity for designing a switchboard to provide
for future extensions, for the most economical distribution of bus
bar copper, and to provide means for measuring the total load.

When a switchboard comprises generator, totalizing, and
feeder panels only, the standard arrangement of panels when
facing the front of the switchboard is to place the generator panels
at the left, the feeder panels on the right, and the load or instru-
ment panels between the two.

Bus Taper. — In fixing any arrangement of panels it is most
practical and economical to locate the heaviest capacity panels
next to the totalizing panels, the lightest capacity panels being
located at the ends. The bus bar copper can then be tapered by

SWITCH BO A HIM—GENERAL INFORM A TION

289

the use of laminated bus bars. This construction reduces the
amount of bus bar copper to a minimum and permits making
extensions easily. A typical layout is shown in Fig. 182.

Location. — In many cases control apparatus and switching
devices can be located to advantage near the machines controlled
and save great expense in ducts and conductors, and avoid un-
necessary complications. Such devices can be made electrically
operated if the control is to be concentrated on one main switch-
board.

These //gvres rtyresef>rB</s

Bar eapoc/fy

po/nfs /nc//r.0/ptf6y

wrt/cfi represent //>epo/nfsa/

i ftotver
Bus

These //gvrts represent

t>ff*err> po/nfs /nt/tcafe*
ty ffrrotv /tetK/s rvri/cri rf-
preseri r/fte p&n fs
ft>MVr /s foAen/rorn fft/f

600 601

Fia. 182. — Typical bus bar tapering.

Copper. — The most economical distribution of conducting
copper is frequently possible with remote controlled switching
devices since the switching apparatus can be located to the best
advantage without reference to the location or width of panels.

The amount of bus copper required for a switchboard equip-
ment depends on the arrangement of panels and the distribution
of circuits.

The amperes allowable per strap in the bus bar will vary ac-
cording to the conditions of installation and service. The shape
and dimensions of conductors, the relative position of conduc-
tors, and, in the case of alternating current, the frequency, all
contribute to fix the effective capacity of a single strap in any
given installation.

Carrying Capacity. — For alternating-current switchboards
for capacities requiring but one strap, a 2-inch X 3^-inch strap
will carry 550 amperes and a 3-inch X M-inch strap will carry
850 amperes at frequencies not greater than 60 cycles. For bus
capacities above 2500 amperes, 60 cycle, or 4000 amperes, 25
cycle, careful designing is needed to secure the proper bus bar
layout. In general, for bus capacities above the values given,

290 • SWITCHING EQUIPMENT FOR POWER CONTROL

the maximum temperature rise of the copper will exceed 28
degrees Centigrade, due to unequal distribution of current in the
busses, since the inductive effect of adjacent busses causes increase
in current density on one side of the respective bus bars and
produces unequal heating of the straps forming the bus. Inter-
lacing of phases or special arrangements of conductors can some-
times be adopted to secure a balance of the mutual inductive
effects, better current distribution and more efficient use of the
copper.

Exciter Bus. — Exciter bus bars ordinarily extend across the
exciter panels and the alternating-current generator panels ; and if
used exclusively for the exciting current, their capacity need not
exceed the total current required by the generator fields. The
standard exciter bus bars for capacities up to 400 amperes is one
2-inch X J^-inch copper strap; up to 600 amperes, one 3-inch X
2^-inch strap; up to 800 amperes, one 3-inch X 34 -inch strap and
up to 1200 amperes, two 3-inch X K-inch straps.

Equalizer Bus. — The cross-section of the equalizer bus bar is
in general made about one-half that of the positive or negative
bus behind the generator panels.

Copper Sizes. — 3-inch X ^-inch copper strap can be used to
advantage for bus bar capacities up to 4000 amperes. 6-inch
X H-inch copper strap can be used to advantage for bus bar
capacities above 4000 amperes up to 8000 amperes, 10-inch X
34-inch copper strap for bus bar capacities above 8000 amperes.

Ultimate Bus Capacity. — In designing a switchboard, an esti-
mate should be made regarding the probable ultimate continuous
bus capacity so that straps of proper dimensions and proper bus
structures or supports can be utilized to take care of probable
future additions.

In cases where the load is a fluctuating one, or the load factor
is low, as in a synchronous converter substation of an interurban
railroad the section of the bus can sometimes be safely reduced
below that figured from the usual table.

Tubing — Carrying Capacity. — In high tension layouts, 22,000
volts and over, the connections and bus bars frequently consist of
brass or copper tubing, iron pipe sizes. This tubing in standard
lengths can be furnished on order when required.

The carrying capacities given below are based on a tempera-
ture rise of 28 degrees Centigrade. The sizes are iron pipe sizes.

For connections of moderate length, the capacity of 1^4 -inch

SWITCHBOARDS— GENERAL INFORMATION

291

copper tubing may be increased to 800 amperes, other sizes in
proportion.

Size of pipe,

Area in

Amperes

inches

circular mils

Copper bus

Brass bus*

Iron busf

314,975

250

426,816

350

601,381

500

100

884,176

725

145

*20 per cent, conductivity.

fl2 per cent, conductivity.

Panel Ratings. — The ampere rating of a switchboard panel
corresponds to the capacity of the switches or circuit breakers
mounted on the panel or controlled from it. The switches and
circuit breakers are rated in accordance with the National Elec-
trical Code and will carry their rated current continuously.

Switches and circuit breakers are given a maximum rating as
they reach a final temperature quickly when carrying a steady
current. Their capacity must, therefore, correspond to the one
or two-hour overload capacity of the machine or circuit, if such
a rating exists, in addition to its continuous capacity.

Temperature Rise. — The usual temperature rise guarantee
for switchboard apparatus when carrying its rated current is 28
degrees Centigrade for knife switches, 30 degrees Centigrade for
conducting parts of carbon and oil circuit breakers, and 50 degrees
Centigrade for circuit-breaker coils and frames. Bus bars and
connections are proportioned so as not to exceed 28 degrees Centi-
grade rise and instrument transformers are not allowed to exceed
50 degrees Centigrade. Shunts and resistances are exempt from
temperature limitations. A room temperature of 40 degrees
Centigrade is used as a basis. Where the room temperature ex-
ceeds this value, larger capacity apparatus should be chosen in
order that the ultimate temperature will not exceed those fixed on
this basis.

The maximum possible setting of overload circuit breakers
should not be less than the momentary overload capacity of
the machine or circuit.

Ammeter Scales. — Ammeters are commonly furnished with
full scales corresponding to approximately 125 to 150 per cent, of

292 SWITCHING EQUIPMENT FOR POWER CONTROL

the ampere rating of the panel. This allows for overload swings
and yet gives good readability of scale at normal load. For
railway service, D.C. ammeters are furnished with scales for the
momentary overload capacity of the machine.

Switching Apparatus. — The switching apparatus on direct-
current circuits consists of knife switches and carbon circuit
breakers. Oil circuit breakers are not applied on D.C. circuits,
as the breaking distances are proportioned for alternating current
and are not great enough for direct current. In an A.C. circuit
the current goes to zero with every alternation, thus assisting
in breaking. The direct- current arc has a greater volume for the
same current, and, besides requiring greater distances and oil
volumes, the oil carbonizes much more rapidly, thus impairing
its insulating value.

Oil Breakers. — Non-automatic oil circuit breakers can be used
on standard high voltage direct- current arc lighting panels where
the circuit is not over 10 amperes, and where the breakers are
always opened by hand and then only infrequently. The recti-
fier arc regulators are commonly disconnected by opening the
A.C. primary breaker first so that the D.C. secondary breaker need
not be opened under load. Oil circuit breakers are used princi-
pally for the control of alternating current, and, hence, find their
greatest application in connection with A.C. switchboards.

Ratings. — They are rated as to voltage, amperage, frequency,
interrupting capacity and instantaneous current- carry ing ca-
pacity. The voltage rating is the maximum voltage at which the
breaker may be used and still meet standard A.I.E.E. rules
on voltage tests. If the nominal voltage of the system equals
the breaker voltage rating, which is a maximum, then in general
the next higher voltage breaker should be used. The ampere
rating is the maximum current for its guaranteed temperature
rise.

Interrupting Capacity. — The ampere interrupting capacity
of a circuit breaker is the highest current which it will open at
any specified normal voltage, frequency, and duty. This ca-
pacity depends on the construction of the breaker. The duty
on which ampere interrupting values are based assumes that the
breaker will interrupt a circuit twice in succession at an interval
of 2 minutes and then be able to carry its normal current until
such time as it is convenient to inspect it and make necessary
adjustments.

SWITCHBOARDS— GENERAL INFORMATION 293

In order to protect the circuits controlled by a switchboard
from damage due to sudden overloads some device may be con-
nected in the circuit that will automatically break it when an
overload is applied. The devices used are fuses or automatic
carbon or oil circuit breakers, depending on the nature of the cir-
cuit or apparatus to be protected.

Meter Equipment. — The selection of the proper meter equip-
ment for a switchboard depends on the class of board employed,
the number of lines controlled, etc. In general, a careful selec-
tion of suitable meters is of more importance on the larger boards,
especially the electrically operated, than on the smaller ones,
for the reason that many more economies can be introduced in
the operation of a large station by skilled operators with a suitable
meter equipment than would be possible in a smaller plant. On
all boards, a multiplicity of meters should be avoided and only
those necessary to give the information desired should be used.

D.C. Meters. — On D.C. switchboards, the meter equipment
is usually quite simple, consisting generally of one voltmeter
arranged for switching to each generator circuit, one ammeter
for each generator circuit, and an ammeter only for the feeder
circuits except in cases where feeders may be energized from an
outside source, when provision should be made for reading the
feeder voltage. On the smaller boards, the ammeter may be
dispensed with on the feeder panels.

A.C. Meters. — When the load is not always balanced, alter-
nating-current generators should be equipped with an ammeter
in each phase, or with one ammeter and a polyphase ammeter
switch if simultaneous readings are not desired. In case the
load is always balanced, a single ammeter is all that is necessary.

If generators operate in parallel they should have an indicat-
ing wattmeter and a field ammeter in addition to the main am-
meter. If cost is a serious consideration, either one may be
omitted but not both.

Indicating Wattmeter. — This will indicate the total instanta-
neous energy load on the machine regardless of power factor or
distribution of load. Two machines of the same size operating
in parallel may have the same curent output, but, through im-
proper field adjustment one machine may be supplying all the
load or even driving the other machine as a motor, without the
ammeters indicating any abnormal condition.

Field Ammeter. — This serves to indicate the proper adjust-

294 SWITCHING EQUIPMENT FOR POWER CONTROL

ment of field current so that windings will not be overloaded.
It is also convenient as a means of determining the cause of any
abnormal conditions in the generator.

Power factor meters or reactive factor meters may be used in
addition to, or in place of, indicating wattmeters, but a com-
parison of the wattmeter reading with the corresponding readings
of the voltmeter and ammeter will give a general indication of
machine power factor.

Bracket Instruments. — Voltage readings of machines in paral-
lel are usually taken by means of a "machine" voltmeter (which
is usually mounted on a swinging bracket) connected to volt-
meter switches on the individual panels. Most operators desire
a second voltmeter mounted on the same bracket with the ma-
chine voltmeter and connected permanently to the bus bars.
This arrangement permits a simultaneous comparison of the
bus bar and machine voltages when synchronizing.

A synchronoscope, mounted on a swinging bracket, for indi-
cating synchronism when connecting an incoming machine to
the bus bars, usually forms part of the equipment. This instru-
ment is often supplemented with two 110-volt indicating lamps,
connected to be dark at synchronism, to be used as a check and
as a reserve in case the synchronoscope is removed temporarily.
A machine or bus frequency meter is frequently advantageous.

Feeders. — Alternating-current feeder circuits are usually sup-
plied with ammeters as a general indication of the feeder load.
Other meters such as frequency meters, power factor meters,
indicating wattmeters, watt-hour meters, etc., are supplied ac-
cording to the requirements of each particular case.

Ground Detectors. — Ungrounded systems should be equipped
with some form of ground detector for indicating grounded cir-
cuits. For systems up to and including 600 volts, the ground
detector usually consists of incandescent lamps capable of with-
standing full bus bar voltage, connected in series from each bus
bar to ground, so as to form a continuously indicating detector.

For 2200 volts and above, static ground detectors may be
used. These are operated from condensers or resistors connected
to the bus bars in order to obviate danger from high voltage in
the instrument. The detectors must be rigidly mounted so that
the position of the leads cannot be changed.

Rheostats. — Field rheostats are usually operated by means of
a handwheel on the front of the panel, from which a shaft ex-

SWITCHBOARDS— GENERAL INFORMATION 295

tends through the panel to the rheostat, or to a sprocket for
remote control.

Rheostats that are sufficiently small, such as exciter field rheo-
stats and voltage limiting rheostats, may be supported on a tet-
rapod mounting on the rear of the board immediately back of
the handwheel and operated directly through the shaft.

In practically all cases, however, generator field rheostats
should be mounted apart from the switchboard and operated
through a sprocket-and-chain transmission except where elec-
trical operation is desired. The faceplates are usually mounted
directly on the resistance frames and wired completely before
shipment. When individual exciters are used with the genera-
tors, the exciter field rheostat may be mounted in combination
with the generator field rheostat. With this mounting, the
handwheels and shafts for the two rheostats are mounted con-
centrically, the main rheostat being controlled through the outer
shaft and the exciter rheostat through the inner shaft.

Safety Code. — On account of the general adoption of the Na-
tional Safety Code either as a legal requirement or as a standard
of reference in courts of law in many states, with the probability
that it may become the basis on which all safeguards against
accident or damage to persons are provided, it is recommended
that the Code be taken into account in the application, installa-
tion and operation of the switchboard apparatus. In general,
the purchaser should provide a competent operator and such
guards, shields, insulating mats, isolation, warnings, and other
requirements to make the installation comply with the Code as
may be recommended, unless he does otherwise at his own risk.

CHAPTER XII

SMALL D.C. & A.C. SWITCHBOARDS

For small industrial plants, hotels, garages, etc., switchboards
with panels 48 inches high or less mounted on light pipe frame-
work are built by various manufacturers. While the practice
of the different builders naturally varies, the descriptions that
follow may be taken as fairly representative of this class.

BATTERY CHARGING PANELS

Sectional Type. — The sectional type of battery- charging
panels on single frame shown in Fig. 183 are designed primarily

FIQ. 183. — Sectional type of battery charging board.

for use in public and private garages where electric vehicles will
be charged. The charging rheostats specified are designed for
charging batteries recommended by the Society of Automotive

296

SMALL D.C. AND A.C. SWITCHBOARDS 297

Engineers, namely, 40 to 44 cells for lead batteries and 60 to 62
cells for Edison batteries.

Each panel consists of three or more sections, together with
charging rheostats. This sectional construction provides a
large variety of combinations, thus making an installation very
flexible, as the number of charging circuits may be increased at
any time after the switchboard has been installed, by the addi-
tion of suitable sections and rheostats.

Rheostat. — Each battery-charging rheostat consists of a resist-
or of cast-iron grids supported on the rear of each panel section
between steel end frames with contact buttons and moving arm
on the front of the panel section. Bolts through the panel hold
the end frames of each charging rheostat to the panels so that
the rheostat forms an integral part of the section equipment.
By disconnecting the wires connecting the grids to the contact
button terminals, the resistor can be easily removed from the
panel.

Assembly. — The sections of each panel are assembled one
above another and securely bolted to a vertical angle iron frame
of suitable height. The simplest panel consists of one or more
charging sections and a power control section mounted above the
charging sections. Swinging brackets at the side of the panel
will mount the power section ammeter, if used, and the battery-
voltmeter and ammeter. It is not advisable to use panels ex-
ceeding 90 inches in height, because some of the switching ap-
paratus would be inconveniently high for the operator, and,
therefore, when more sections are required than can be mounted
on a frame 90 inches high, they may be arranged in two or more
panels of uniform height. Where the number of necessary sec-
tions is not sufficient to make all panels the same height, blank
sections may be provided for some of the panels.

Generator Section. — Every switchboard or panel which con-
trols one or more direct-current generators must be equipped
with an individual power control section for each generator. If
generators are compound wound and generator control sections
with circuit-breaker protection are used then one side of the
generator switch will be connected to the equalizer bars, the
other side to the negative bus, and the circuit-breaker will be
connected in the positive lead. If generator control section
provides fuse protection only, then an equalizer switch must be
provided.

298 SWITCHING EQUIPMENT FOR POWER CONTROL

Locations. — A rule, incorporated in the National Electric Code,
specifies that charging panels located in garages where gasoline
is handled must have all spark producing devices mounted 4
feet or more above the floor. If such devices are mounted less
than 4 feet above the floor, the charging panel must be surrounded
by a vapor-proof enclosure, unless the panel is located in a room
or enclosure provided for this purpose.

Platform. — Switchboards or panels controlling several charging
circuits will regularly have the switching apparatus mounted less
than 4 feet above the floor and the purchaser is expected to install
the panels as provided for by the Code. In most cases, the
simplest method is to mount the board on a concrete platform
4 feet high.

Protection. — The arrangement of the panel sections, and com-
bination of them, is such as to provide a maximum of protection
to the operator. Power control sections employing carbon circuit
breakers will be located at the top of the panel. The contactors
on the charging sections are provided with blowout coil and
shields. The operator is thus protected against possible injury
due to moving parts or to the arcing of automatic devices.

The various sections are made up of slabs 1 inch thick,
K-inch bevel. These sections are of two heights, 14 inches
and 28 inches, depending upon the apparatus mounted on the
section.

Ampere-hour Meter Sections. — These are equipped with
ampere-hour meters of the auto type, with a zero contact reset
device and variable resistor element. The meter is designed so
that it will run "slow," when the charging current of a battery
passes through it, the speed being adjustable to approximately
compensate for the charging efficiency of any battery. When a
given number of ampere hours for which the meter has been set
have been supplied to the battery, the pointer will again be at
the zero position and will close the zero cont act. This will cause the
contactor in the circuit to open, thus terminating the charge.
Therefore, to charge a battery, it is only necessary to set the meter
pointer at the ampere hours, as previously discharged from the
battery, and when this number of ampere hours (automatically
corrected for charging efficiency by the resistor element of the
meter) have been returned to the battery it will be automatically
disconnected.

When ampere-hour meter sections are used, for the purpose of

SMALL D.C. AND A.C. SWITCHBOARDS 299

automatically terminating the charge of a battery, it is neces-
sary to use charging sections, employing a contactor.

Rheostats. — Each power control section to be used for the
control of a direct-current generator is drilled for a field rheostat
mounting of the switchboard type.

Each switchboard that controls a source of power such as a
direct-current generator must be equipped with a ground detector
outfit. For such panels, two 110- volt incandescent lamps are
furnished and are mounted with the generator ammeter on the
swinging bracket. Each of the lamps is connected between one
side of the line and ground, thus forming a continuous indicator.
Under normal conditions each lamp will glow red due to the fact
that it is operating on about one-half normal voltage. If the
positive line becomes grounded, the lamp connected to that line
will grow dim or cease to glow at all, while the other lamp will in-
crease in brilliancy. If the negative side is grounded, the order
of brilliancy is reversed. When power is received from incoming
direct-current lines the lamps are not required.

Overload Protection. — Plain overload protection is regularly
furnished for all sections. For this purpose there is furnished for
each charging circuit a National Electrical Code fuse holder and
enclosed fuse for each side of the circuit.

To protect the battery ammeter against overload, a fuse is
provided and is connected between the battery ammeter bus bar
and the main negative bus bar. This fuse is regularly mounted
on a bracket on the rear of the panel.

When it is desired to use two or more battery ammeters inde-
pendently, each ammeter must be protected by its own fuse.

If each charging circuit is to be protected against reversal of
current, it is necessary to select charging sections and power con-
trol sections for this service.

Power Control. — Power control sections with circuit breaker
protection are regularly furnished with a low voltage release me-
chanism attached to each circuit breaker to protect the source
of power against reversal of current. When this circuit breaker
opens, due to reversal of current, the auxiliary contacts with
which the circuit breaker is supplied will open all charging cir-
cuits which are provided with magnetically operated switches.

In case power control sections equipped with fuse switch pro-
tection and with low voltage relay switch are used, the reversal
of current will cause the low voltage relay switch to open and

300 SWITCHING EQUIPMENT FOR POWER CONTROL

thereby open all the charging circuits, if charging sections with
contactors are used.

Low Voltage. — The low voltage coil of the carbon circuit
breaker and of the low voltage relay switch will be suitable for
115 volts D.C. In case the generators are driven by A.C. in-
duction motors, it is possible to obtain A.C. low voltage coils,
so that on failure of the A.C. power the low voltage relay switch
and carbon circuit breaker will be tripped.

Reversal. — However, when several generators operate in
parallel and obtain their power from separate sources it will be
necessary to use reverse current relays, in order to insure'absolute
protection against the occurrences of reverse current.

From the battery standpoint, it is very desirable to have bat-
tery circuits protected against reverse current. If only the gen-
erator or main circuit is protected against reverse current, the
batteries remain connected in parallel to the bus bars (after the
circuit breaker opens). Therefore, the batteries having the high-
est terminal voltage will discharge into the other batteries con-
nected to the system.

Reverse Protection. — The use of the low voltage release me-
chanism, as part of the circuit breaker equipment, or the use of
the low voltage relay switch, is adaptable for protection against
the reversal of current from a storage battery, because at ordi-
nary temperatures (from 60 degrees to 90 degrees Fahrenheit) the
voltage of a good battery discharging at the normal rate is always
lower than the minimum voltage required to start the charging of
that battery at the normal starting rate. Furthermore, the charg-
ing resistance connected in series with the battery further reduces
the voltage across the coil of the circuit breaker 'or the low voltage
relay switch (upon reversal of battery current), thus insuring the
tripping of the breakers or the low voltage relay switch.

Meter Switch. — Each charging section is equipped with a
special 2-pole knife switch which may be moved to a position
(without opening the circuit) so that the battery ammeter and
voltmeter are connected to the charging circuit, thereby indicat-
ing the charging rate in amperes and the voltage of the battery
at once.

Rheostats. — The battery-charging rheostats usually provide
12 steps. The standard rheostats are usually designed for a
particular number of cells. However, each rheostat may be used
for charging a battery composed of a slightly larger number of

SMALL D.C. AND A.C. SWITCHBOARDS

301

cells, requiring the same charging rate, but it must be observed
that in this case the number of resistance steps available for
adjustment will be reduced. If a battery is to be boosted at a
rate higher than that scheduled, a special rheostat will be
required.

Lead Batteries. — For lead batteries, the voltage applied across
the battery terminals will be increased as the charge progresses

r Charging!
^ —-.

FIG. 184. — Diagram of connections with magnetically operated switches.

and the charging current will be maintained approximately con-
stant, that is, at the given starting rate until near the end of the
charging period; then the current will be reduced to a given
finishing rate, and will be maintained approximately constant
throughout the remainder of the charging period.

Edison Battery. — For nickel-iron (Edison) batteries the voltage
applied across battery terminals will be increased as the charge

302

SWITCHING EQUIPMENT FOR POWER CONTROL

progresses and the charging current will be maintained approxi-
mately constant at the required rate.

Connections. — Fig. 184, shows the diagram of connections
with magnetically operated switches.

LIGHTING AND CHARGING PANELS

Light and Battery. — Where a switchboard is desired for con-
trolling the charging of batteries used in lighting service and on
electric vehicles, but only one battery is to be controlled instead
of using the sectional type a somewhat simpler construction is
employed as shown in Fig. 185.

FIG. 185. — Light & battery panels.

One class of panels is intended for use in residences and small
isolated plants that have a battery to supply current for light-
ing and a generator for charging the battery. Only single panels
are made and the capacity of the generator panels is limited to
75 amperes, while the battery panels are limited to a normal ca-
pacity of 60 amperes. On single section panels the limit is 100

SMALL D.C. AND A.C. SWITCHBOARDS 303

amperes for both generator and battery circuits. The circuit
breakers are equipped with reverse current attachments in ad-
dition to the plain overload trip which will open the circuit in
case the charging current is interrupted, and thus prevent the
discharge of the battery.

When battery-charging apparatus is required with a generator
panel, it will be mounted as a lower section of the panel, except
when a single section generator and battery-charging panel
is specified.

Conditions. — Three conditions are provided for in charging
batteries with these panels:

First, 50-volt generator charging 30-volt battery connected
directly to the mains.

Second, 125-volt generator charging 30-volt battery. The
battery is charged through a suitable resistance.

Third, 125-volt generator charging 125-volt battery. The
battery, in this case, is charged with two sections in parallel,
each section being connected through a suitable charging resist-
ance. A fixed resistance is used for this work, the variation in
voltage being taken care of by varying the field of the generator.

Constant Potential Charging. — This method of charging is the
constant potential charging method; that is, the battery is thrown
directly on the circuit and allowed to become charged. When
the battery and charging circuit voltages differ sufficiently to
produce a charging current of such a value that it may be injurious
to the battery, a charging resistance is necessary. The value of
the resistance depends on the number of cells in the battery;
type of cells (or voltage at beginning of charge and at the end of
charge) ; charging current desired ; and the line or generator voltage.
A variable resistance, that is provided with faceplate and rotating
arm, mounted apart from the board, can be used to obtain the
constant current method of charging. However, if there are
but one generator and one battery circuit, the constant current
can be obtained by adjusting the generator field rheostat.

Generator Battery. — Where a panel is chosen to control
a lighting circuit in addition to generator and battery circuit,
the generator voltage must be maintained for the lighting circuit,
and consequently a charging resistance is necessary, either of the
fixed or variable type. Electric vehicle charging panels are made
for private service, where one battery is to be charged and the
charging current is taken from an outside source. They can,

304 SWITCHING EQUIPMENT FOR POWER CONTROL

however, be used when the current is furnished by a motor-genera-
tor set or engine driven generator, by adding the field rheostat
for the generator to the panel and in the case of the motor-genera-
tor sets by mounting one of the lower sections on the same frame.
The reverse-current mechanism furnished with the carbon
circuit breaker depends for its action on the sum of the voltage
and current coil fields. The voltage coil field is the stronger

field on small reversal and strong
enough at zero current setting
of the reverse-current devices to
trip the breaker.

Panels. — The generator panels
are a modification of the small
generator panels described later
in that the circuit breaker is
equipped with reverse-current
trip. The current coil in the
relay is designed for the same
carrying capacity as the circuit
breaker and the relay is cali-
brated to operate with a battery
which has the same capacity as
the generator, or greater. In
case the battery is so small that
it requires only a portion of the
generator capacity to completely charge it, a special relay or
extra switches may be required. Lower sections are provided
which correspond in type to the lower sections regularly used
with the generator panels.

The lower sections are for use with 30-volt batteries, and with
125-volt batteries. These when combined with the generator
panel form the complete panel for controlling generator and bat-
tery for private service.

Fig. 186 shows the connections of a single section battery
panel charging the battery with all cells in series.

COMBINATION GENERATOR AND FEEDER PANELS

Where the panel is not used with a battery the reverse-current
attachment is left off the breaker and the panels are designed to
provide a complete switchboard in a single panel of one or two
sections to control one generator with not more than four feeders.

FIG. 186. — Connections of generator
and battery panel.

SMALL D.C. AND A.C. SWITCHBOARDS 305

They are intended for small isolated plants operating direct-
current systems of 250 volts or less.

Limits. — The capacity of a panel is limited to 400 amperes for
the generator, and 200 amperes for each of two feeder circuits,
or for 60 amperes for each of four feeder circuits. Each panel
forms a complete switchboard and is not designed to have panels
added to it.

Panel Size. — The panel consists essentially of either one or two
sections of slate 1 inch thick, 16 inches wide, with ^-inch bevel
on front edges; the upper section being 24 or 36 inches high, and
the lower section, 12, 18 or 24 inches high. The upper section
contains the apparatus for the control of the generator and the
lower section contains that for the control of the various feeder
circuits.

Frame. — The frame is light and simple, being made from %-
inch gas pipe uprights which are screwed into floor flanges. The
total height of the frame is 65 inches. It is fitted with wall brace
ends for ^-inch gas pipe. Pipe and foot for bracing the frame to
the floor or wall can be supplied at a small additional price.

Switches. — Single-throw knife switches are used for generator
and feeder circuits. When it is desired to provide for a separate
source of power, the generator panel can be furnished with a
double-throw switch. This switch will be mounted horizontally
instead of vertically.

Protection. — Automatic protection is provided for the gene-
rator circuit by a single-pole carbon circuit breaker, or by en-
closed fuses mounted on the front of the panel. Feeder circuits
are protected by enclosed fuses mounted on the front of the panel.

SMALL PLANT SWITCHBOARDS

The next larger size of D.C. panels using slabs 48 inches high
on pipe framework are particularly adapted to the control of
from one to three generators in small industrial plants and cen-
tral stations operating direct-current 2 wire systems of 250
volts or less.

Limits. — The capacity of a single generator panel is limited
to 600 amperes, and that of a complete switchboard composed
of these panels to 1500 amperes, with the number of panels limited
to six. For greater capacities, a switchboard composed of 90-
inch high panels is recommended.

306 SWITCHING EQUIPMENT FOR POWER CONTROL

Panels. — Each panel consists of a single slate slab 48 inches
high by 12, 16, 20 or 24 inches wide, 1% inches thick, with 96-
inch bevels on front edges, bolted at the four corners to the
switchboard frame. This frame is made of lK-inch pipe up-
rights, resting on floor flanges and supporting the necessary panel
and top iron brackets, to which the panel is bolted. The total
height of the panel is 76% inches.

Automatic protection is provided for the generator circuits by
single-pole carbon circuit breakers, or enclosed fuse blocks
mounted on the front of the panel ; for feeder circuits by single-
pole carbon circuit breakers, enclosed fuse blocks on slate bases
mounted on brackets on rear of panel.

MINING SWITCHBOARDS

Switchboards of this type are suitable for substation service in
mining installations controlling motor-generator sets or synch-
ronous converters typical panel arrangements being in line with
Fig. 187 with connections as shown on Fig. 188.

Syn DC DC

Motor Panel Gen Panel Gen Panel.

Starter- -L-J

Remote Mechanical Control.
FIG. 187. — Arrangement of M.G. panels for mine service.

Scope. — These mining panels are particularly adapted for the
control of small direct-current generators and A.C.-D.C. motor-
generator sets, operating 2-wire, grounded negative, direct-
current systems of 600 volts or less; and for the control of small
275-volt converters for mine service, operating 2-wire, grounded
negative, direct-current systems.

Engine Generators. — Panels for the control of 275-volt, direct
current, engine driven generators are in general similar to gene-

SMALL D.C. AND A.C. SWITCHBOARDS

307

rator panels shown, except the connections on the rear are made
for a grounded negative with one pole of the 2-pole circuit
breaker being connected between the armature and the series
field and equalizer connections, and the other between positive
and bus. As the negative side of the circuit is grounded, no

FIG. 188.— Diagram of connections for M.G. sets for mine service.

ground detector outfit is supplied. The voltmeter switch is two
point, the negative side of the voltmeter being connected to
ground.

Panels for the control of 600-volt, engine driven generators are
similar to the 275-volt panels described above, except that 600-
volt apparatus is supplied.

Motor Generators. — Panels for the control of direct-current
generators which are part of motor-generator sets, with over-

308 SWITCHING EQUIPMENT FOR POWER CONTROL

load protection in the motor circuit, will have the connections
modified in that the single-pole carbon circuit breaker will be
inserted in the positive side of the circuit. The carbon breaker
will also be equipped with a low voltage release for tripping it
when the motor breaker opens.

Feeders. — Panels for the control of feeders are similar to light
and power feeder panels, except that a single-pole knife switch
is furnished in place of each 2-pole switch, and the switches
are for 600 volts for the 600-volt panels.

Motors. — Panels for the control of induction motors are
furnished in the form of sub-panels to be mounted directly below
the direct-current generator panel, on the pipe frame legs.

Panels for the control of self-starting synchronous motors are
furnished as separate switchboard panels to stand adjacent to
the direct-current generator panel.

Starters. — The A.C. motor starter is a double-throw oil circuit
breaker, non-automatic for starting, and automatic with over-
load inverse time limit and low voltage release for running. The
handles are mechanically interlocked so that the starting side of
the breaker must be closed first and that the running side can
only be closed within a fixed time interval after starting side had
been opened.

The starting position magnetizes the auto transformers and
connects the motor to the starting voltage, the tap leads of the
transformer being permanently connected to the motor leads.
In passing to the running position the auto transformers are
disconnected from the line and full-line voltage is applied to the
motor.

The starter for 3-phase service is 4-pole double throw with
special moving contact arrangement.

Starting Combinations.-^-As an alternative, a combination of
remote mechanically operated automatic 3-pole and non-auto-
matic 4-pole type breakers can be had. The 3-pole breaker
constitutes the running breaker. It is overload automatic, with
inverse time limit and low voltage release mechanisms. The 4-
pole breaker is the starting breaker; it magnetizes the auto trans-
formers and connects the motor to the starting voltage from
separate handles mechanically interlocked so that one breaker
only can be closed at one time. A two handle cover plate will be
supplied and current transformers for use with the automatic
breaker.

SMALL D.C. AND A.C. SWITCHBOARDS 309

This combination is made for remote mechanical operation
only and is applicable only for starting with two single-phase
auto transformers.

The switching equipment for motors of capacities exceeding the
ratings of the double-throw breaker are made up of either two or
three single-throw breakers as follows:

Motors started by means of two single-phase auto transformers
have a standard 3-pole running breaker and a special 4-pole start-
ing breaker; motors started by means of a 3-phase auto trans-
former have a standard 3-pole running breaker and two special
3-pole starting breakers operating in tandem.

Time Element. — The inverse time element feature is provided
in connection with the overload trip on the circuit breaker or au-
to starter, so that the motor circuit will not be opened on moment-
ary overloads, such as obtain when the switches are moved from
the starting to the running position. The time in which the over-
load trip will operate is inversely proportional to the amount of
overload, tripping being instantaneous in case of a short circuit.

The overload tripping range is usually from 80 to 160 per cent,
of the current rating of the current transformers included with
the panel equipment.

Low Voltage. — All circuit-breaker equipments have a low
voltage trip which opens the running breaker when the voltage
has dropped to approximately one-half its normal value. This
feature is included to guard against an excessive current due to
the return of power to a motor which may be out of phase or at
rest. For voltages up to and including 550, the low voltage coil
with series resistance is connected directly to the line. For higher
voltages, a voltage transformer with primary fuse blocks and
fuses is included.

Auxiliary Switch. — The handle of the running circuit breaker
is equipped with an auxiliary switch which serves to operate the
low voltage trip circuit of the direct-current generator breaker of
the motor-generator set, when the alternating-current breaker
opens.

Reversal. — If the direct-current generator of a motor-generator
set operates in parallel with an independent source of direct-
current power, the set will run inverted upon the interruption of
the alternating-current power and hold up the alternating-current
voltage. The independent source of direct-current powermay be
a motor-generator set (or a synchronous converter) supplied

310 SWITCHING EQUIPMENT FOR POWER CONTROL

from a separate alternating-current source, a generator driven
by a prime mover, or a battery. In order to prevent motoring
from the direct-current bus bars, and to disconnect the set, a
reverse-current relay should be included with the direct-current
generator panel equipment and so connected as to trip the alter-
nating-current breaker upon current reversal. With the
electrical interlock mentioned in the preceding paragraph the
direct-current breaker is tripped on the opening of the alter-
nating-current breaker and the set is thus completely discon-
nected in case of alternating-current power interruption.

Rupturing Capacity. — The short-circuit amperes which the
breaker may be called upon to interrupt must be considered in
every case before applying the standard equipments. If the total
capacity of generating and synchronous apparatus connected close
to the motor is sufficient to deliver, under short circuit, a current
in excess of the rupturing capacity of the running breaker in-
cluded in the standard equipment, special consideration is neces-
sary. It may be possible in this case to modify the standard
equipment by replacing the dashpot inverse time limit attach-
ment by direct trip attachment, and relay equipment giving a
definite minimum time delay, and thus avoid the necessity of a
heavier duty breaker. Where the interrupting capacity required
is more than twice the rating of the breaker in the standard equip-
ment, it is necessary either to replace the running breaker by one
of suitable interrupting capacity or supply a breaker of suitable
interrupting capacity in series, which is set to open ahead of the
running breaker of the standard equipment in case of a short
circuit. The breaker at the power house may often serve this
purpose where the motor is supplied from a transmission line.
In the latter case the breaker of the standard equipment must be
given a definite minimum time delay as mentioned above. It
may be necessary also to use heavier duty starting breakers on
a heavy capacity system.

Auto Reclosing Breakers. — These circuit breakers can be
applied where it is desired to insure that circuits will not unneces-
sarily remain open when overload conditions have been removed.
Power is automatically put back on the circuit, as soon as con-
ditions permit, and the expensive delays due to failure of power
is reduced to a minimum.

Automatic reclosing circuit breakers can be furnished in place
of the plain, automatic, carbon breakers. The automatic re-

SMALL D.C. AND A.C. SWITCHBOARDS 311

closing circuit breaker is essentially a solenoid operated breaker,
the main contacts being held closed by the action of a solenoid.
When an overload or short circuit occurs on the load side of the
line the solenoid circuit is caused to open. This remains open for
a definite time, resulting in an immediate opening of the carbon
breaker (owing to a dashpot element), and then automatically
closes only when the overload or short circuit has disappeared.
Auxiliary devices are usually necessary.

When two or more generators operate in parallel and each
generator circuit is provided with an automatic reclosing
breaker, a special master relay is required so that all generator
breakers will be opened or closed simultaneously.

When the feeder circuits are not independent, but tie in with
feeder circuits from other stations, a feeder relay is required with
each tie-in feeder circuit to control the reclosing of the automatic
reclosing breaker with reference to the load conditions, whether
the line is energized from the remote source of power or not, at
the particular time the breaker opens. This applies also to the
automatic reclosing breaker of the generator circuit if there is
only one connected to the bus from which several tie-in feeder
circuits are fed, or to the master relay if there are several genera-
tors operating in parallel on a tied-in system.

When there is the possibility of a reversal, the generator
breakers should also be equipped with a special reverse current
relay which slips over the studs of the breaker.

Synchronous Motor Panels. — These usually have no field
switches. A self-starting synchronous motor is usually started
with the field circuit closed through the armature of its individual
exciter if connected to the motor shaft; or if no exciter is provided
and the motor is excited from the direct-current generator which
it drives, the motor field is closed through the generator armature.
The motor field is thus short-circuited at stand-still and is gradu-
ally excited as the motor comes up to speed.

A 2-pole double-throw field switch must be supplied when
the motor field is excited from a separate source of power, or
from an exciter not connected to the motor shaft. The left-hand
switch studs are connected together by a copper strap. The
field switch is in the left-hand position until the motor has come
up to synchronous speed. It is thrown to the right-hand or
normal position before the motor is connected to full line voltage.

312 SWITCHING EQUIPMENT FOR POWER CONTROL

The rheostat is in series with the field in the starting position as
well as in the normal position of the field switch.

Motor-generator Sets. — When these are used for 275-volt
direct-current service they have the motor field excited across the
direct-current generator terminals. Motor-generator sets for 550
volt direct-current service may have a separate 125-volt exciter
connected to the same shaft, or the motor field may be excited
from an exciter independent of the motor-generator set.

FIG. 189. — Diagram of connections for synchronous converters for mine service.

For synchronous converter service in mines, combination A.C.-
D.C. panels can be supplied containing carbon breaker, ammeter,
voltmeter and knife switch for the D.C. circuit, reactive factor
meter and oil breaker for A.C. with a separate panel for starting
with connections as per Fig. 189.

Combination Panels. — For isolated plant service combination
panels can be provided to control one D.C. generator and any

SMALL D.C. AND A.C. SWITCHBOARDS

313

number of D.C. feeders up to four. These panels are intended
for use in isolated plants operating a single D.C. generator of 250
volts or less and not over 600-amperes capacity.

Each panel consists of a single slate slab, 48 inches high by 20
inches or 24 inches wide, by 1>^ inches thick, with %-inch bevels
on front edges, bolted at the four corners to the frame. The
total height is 76% inches.

Automatic protection is provided for the generator circuit by a
single-pole carbon circuit breaker, or by enclosed fuses mounted
on the front of the panel; for the feeder circuits, by enclosed fuses
mounted on the front of the panel.

The main connections on the back of the panels are of bare
copper strap and are cut, bent, and assembled before shipment.

FIG. 190. — Connections of three-wire
generators with four-pole breaker.

FIG. 191. — Connections of three-wire
generators with two-pole breaker.

Three- Wire Panels.— These 48-inch high panels are also suit-
able for use with 3-wire D.C. generators connected to utilize
4-pole circuit-breaker protection as shown in Fig. 190, or
2-pole circuit- breaker protection as shown in Fig. 191.

These 3-wire switchboards are designed for the control of
from one to three generators in lighting and power plants of
moderate capacity operating direct-current 3-wire systems.

The capacity of a single generator panel is limited to 600 am-
peres, and that of a complete switchboard composed of three
panels to 1500 amperes. For greater capacities a switchboard
composed of 90-inch high panels is recommended.

314 SWITCHING EQUIPMENT FOR POWER CONTROL

Each panel consists of a single slate slab 48 inches high, 1%
inches thick, with %-inch bevels on front edges, bolted at the
four corners to the frame. The frame is made of 1^-inch pipe
uprights, resting in tapped floor flanges with the necessary panel
and top iron brackets. The total height is 76% inches.

Meters. — Polarized ammeters and voltmeters are regu-
larly furnished with these panels. With the ammeters there are
supplied ammeter shunts for mounting on the generator frame,
and shunt leads 40 feet long.

Switches. — Knife switches, either single or double throw, are
used on generator and feeder panels. Switches are not provided
for disconnecting the balance coils from the collector rings on the
generator, as these circuits can be opened by lifting the collector
brushes. If switches are desired in these circuits, double-pole
single-throw knife switches can be provided and mounted on the
panel, or on a sub-panel. The omission of these switches from
the balance coil circuits effects a saving, as it eliminates the
necessity of running cables from the collector brushes and balance
coils to the switchboard.

Protection. — Automatic protection for the generator circuit is
provided by a 4-pole carbon circuit breaker automatically trip-
ped through relays actuated by the full armature current, or by
a 2-pole double coil overload carbon breaker.

Automatic protection for feeder circuits is provided by 2-
pole circuit breakers, three single-pole circuit breakers actuated
by a common trip, or enclosed fuses.

Where generators are operating in parallel, positive and nega-
tive equalizer bus bars are necessary in addition to the main bus
bars. These extend behind the generator panels but are not
continued back of the feeder panels.

Code Rule. — With 3-wire direct-current generators, the
National Electrical Code requires that the "safety device consist
of either a double-pole double coil overload circuit breaker, or a
4-pole circuit breaker connected in the main and equalizer
leads, and tripped by means of two overload devices, one in each
armature lead." In short, the National Electrical Code re-
quires that the safety device be actuated by the full armature
current.

Comparison. — A Comparison between the two methods shows
the following:

SMALL D.C. AND A.C. SWITCHBOARDS 315

Two-pole breaker protection requires:
2-pole carbon breaker.

Six leads between generator and switchboard. (See diagram of con-
nections.)

Cable duct and installation of same for six main generator leads.
Ammeter shunts mounted on switchboard.
Two sets of short ammeter shunt leads.
Four-pole breaker protection requires:

4-pole carbon breaker with low voltage release device for tripping by

relays.

Two overload relays.

Four leads between generator and switchboard. (See diagram of con-
nections.)

Cable duct and installation of same for four main generator leads.
Ammeter shunts mounted on generator frame.

Four sets of ammeter shunt leads of a length at least sufficient to reach
from ammeter shunt on generator frame to meters and relay on board,
through main lead or separate ducts.

Costs. — From the above comparison, it can be seen that the
cost of the switchboard panel equipment is greater with the
4-pole breaker protection than with the 2-pole breaker protection.
However, the added cable and cable duct cost, including also the
added expense of installation, may be found to make the cost of
the total equipment greater with the latter method of protection
than with the former. This becomes true as the distance be-
tween the generator and the switchboard increases, and as the
size of the cables and ducts increases.

The following table gives the distance between generator and
switchboard beyond which it will be found in general that the total
equipment cost of 2-pole breaker protection will be greater than
total equipment cost of 4-pole breaker protection.

200 kw. 250-volt generator 18 feet

150 kw. 250-volt generator 22 feet

100 k\v. 250-volt generator 28 feet

75 kw. 250-volt generator 33 feet

60 kw. 250-volt generator 38 feet

50 kw. 250-volt generator 40 feet

25 kw. 250-volt generator 50 feet

WELDING PANELS

For welding service 48-inch panels can be utilized to ad-
vantage. Welding by means of the electric arc is accomplished
by drawing an arc between a metal or carbon electrode of an
electric circuit, and the metals to be welded. The electrode

316 SWITCHING EQUIPMENT FOR POWER CONTROL

is usually the negative terminal of the circuit, whereas the metal
to be welded is the positive terminal. Direct current is commonly
used for arc welding, as it requires less current than alternating
for the same welding effect and also gives the better results.

Processes. — Arc welding is divided into two commercial proc-
esses: Carbon, or Graphite, Electrode Process, in which the
arc is drawn between metal to be welded and a carbon, or gra-
phite, electrode; and the Metal Electrode Process, in which the

arc is drawn between metal
to be welded and a metal
electrode.

The current for arc welding
may be obtained from any
convenient direct-current
source, although it is com-
monly taken from a motor-
generator set. Several weld-
ing circuits can be connected
to one generator circuit, the
number depending on the
capacity of the generating
equipment and on the num-
ber of operators working at
any one time.

Where only one welding circuit is connected to the generator,
both the generator circuit and the welding circuit may be con-
trolled from a single switchboard panel, which is known as a
combination control panel connected as per Fig. 192, or an in-
dividual generator panel may be used to control the generator
and a separate outlet panel to control the welding circuit. Where
several welding circuits are connected to one generator circuit,
the generator may be controlled either from a separate generator
panel or from a combination control panel; in the latter case one
of the welding circuits is connected to the combination panel and
the remainder to outlet panels, while in the former case an outlet
panel must be provided for each welding circuit.

Capacities. — The combination generator and welding panels
range in capacities from 150 amperes to 1000 amperes for the
generator equipment and up to 750 amperes for the welding equip-
ment. On the 1000-ampere combination panel the control for
the welding circuit is of 750-amperes capacity; on all other combi-

loSh.Fld.

Conc.for use witb Carbon

Electrode or when Reactor

la not furnished.

furnished fcr use tcltb
Metal Electrode only.

: Electrode

FIG. 192. — Diagram of connections for
welding panels.

SMALL D.C. AND A.C. SWITCHBOARDS

317

nation panels the control for the welding circuit is of the same
capacity as the generator circuit. The separate generator panels
are for capacities ranging from 150 to 1000 amperes; the outlet
panels are for capacities of 200, 350 and 600 amperes.

Each panel consists of a single section, 48 inches high by 16,
20 or 24 inches wide, and 1^ inches thick, with %-inch bevels
on front edges, except the metal electrode outlet panel, which is
36 inches high. The panels are mounted on l^-inch pipe frames,
complete with floor brace, the total height of which is 76^ inches.

Single-pole carbon circuit breakers provide automatic overload
protection for both the generator and welding circuits.

p'.o o o
o o

LOW VOLTAGE A.C. SWITCHBOARDS

For moderate capacity low voltage A.C. circuit switchboards
are particularly designed for the control of from one to three gen-
erators in small industrial plants and
central stations operating alternating-
current systems below 500 volts. Fig.
193 shows a typical 440-volt switch
board.

Limits. — The capacity of a single
generator panel is limited to 600
amperes, and that of a complete switch-
board composed of these panels, to 1500
amperes, with the number of panels
limited to five. For greater capacities,
a switchboard composed of 90-inch high
panels is recommended.

Panels. — Each panel consists of a
single slate slab 48 inches high by 16 or
20 inches wide, 1% inches thick, with
%-inch bevels on front edges mounted
on a lK-inch pipe frame. The total
height of the panel is 76% inches.

Protection. — No Overload protection FIG. 193.— Arrangement

is provided for the main or field circuits hL^twitc'hboard We^S'
of alternating-current generators. The

panels for feeder circuits include enclosed fuses mounted on
the rear of the panel.

Meters. — On generator panels, one ammeter is furnished for

318 SWITCHING EQUIPMENT FOR POWER CONTROL

each phase. On feeder panels, one ammeter is furnished for each

2, or 3-phase circuit.

The generator panels are designed to have the exciter rheostat

supported on a tetrapod mounted on the rear of the panel, with
the generator rheostat separately
mounted and operated by a sprocket-
and-chain transmission.

Synchronizing. — These panels are
designed for synchronizing between the
incoming machines and the bus bars.
A six-point synchronizing switch and
an incandescent lamp are furnished
with each generator panel and one
synchronizing key is supplied with each
switchboard, with connections as per
Fig. 194. A synchronoscope with the
necessary voltage transformers can be
supplied, if desired.

Each generator panel is designed to
have the generator field connected
through a 2-pole switch with field

discharge contacts to a single exciter. If parallel operation of

exciters is desired, exciter panels are needed.

FIG. 194. — Diagram of
connections 440 volt A.C.
switchboard.

HIGH VOLTAGE A.C. SWITCHBOARDS

Similar panels are available for 1200-2400 volts and up to 200-
amperes capacity. These switchboards are particularly adapted
to the control. of single or parallel operated alternators in small
industrial plants and central stations, see Fig. 195.

Limits. — The capacity of a single generator or feeder panel is
limited to 200 amperes and that of a complete switchboard to
400 amperes. For greater capacities, a switchboard with 90-inch
panels is recommended.

Panels. — Each panel consists of a single slab, 48 inches high by
13^ inches thick, with %-inch bevels on front edges, bolted at
the four corners to a 1^-inch pipe frame. The total height of the
panels is 76% inches.

Protection. — Standard panels provide no automatic protection
for the main or field circuits of alternating-current generators.

When a single generator panel controlling one feeder is installed,

SMALL D.C. AND A.C. SWITCHBOARDS

319

automatic protection for the feeder side of the non-automatic
oil circuit breaker may be obtained by providing a subsection
with fuses, to be mounted immediately below the generator
panel on the frame. An automatic oil circuit breaker can
be substituted for the non-automatic circuit breaker and fuse
section. The advantages of the automatic circuit breaker are
that it is quickly and easily closed after opening the circuit,

Fia. 195. — Arrangement of small 2400-volt Westinghouse switchboard.

cannot be held in a closed position while an overload condition
exists on the line, and eliminates the trouble and expense of re-
placing the fuses.

The generator panels are designed to have the exciter rheostat
supported on a bracket mounted on the rear of the panel, with the
generator rheostat separately mounted and operated by a
sprocket-and-chain transmission.

Each generator panel is designed to have the generator field
connected through a 2-pole field switch with field discharge

320 SWITCHING EQUIPMENT FOR POWER CONTROL

contact, to a single exciter. If parallel operation of exciters is
desired, exciter panels should be ordered.

Ground Detector. — A voltage transformer having a lamp across
its secondary and arranged for connecting to each bus wire is
supplied for indicating grounds.

Synchronizing. — A synchronizing receptacle and an incandes-
cent lamp for synchronizing between machines are furnished
with each generator panel. The same transformer used in
connection with the voltmeter is used for synchronizing. If
synchronizing between bus and machine is desired, one voltage
transformer with fuses for connecting to bus is needed. A syn-
chronoscope can be supplied if desired.

Feeder panels are supplied with overload automatic oil cir-
cuit breakers or non-automatic oil circuit breakers with rear
connected fuses. These fuses are removable from the front of
the panel, but have no live parts exposed.

CHAPTER XIII

LARGE HAND AND ELECTRICALLY OPERATED PANEL

SWITCHBOARDS FOR D.C. GENERATORS AND

SYNCHRONOUS CONVERTERS

Standards. — For the control of D.C. generators, the D.C. end
of synchronous converters and D.C. feeders for 250 volts, 2-wire
and 3-wire light and power service and 600-volt railway service,
panels with a total height of 90 inches have been standardized
by various switchboard builders. The original Westinghouse
panel divisions for this class of switchboard were 65 and 25 inches,

• FIG. 196. — Westinghouse railway switchboard.

and corresponding G. E. divisions being 62 and 28 inches. The
present three section panels of these companies are 25 inches, 45
inches and 20 inches, and 31 inches, 31 inches and 28 inches res-
pectively. Other switchboard builders have used these or other
panel divisions with the same total height.

Westinghouse Railway Switchboard. — Fig. 196 shows a typical
Westinghouse switchboard installed in a large synchronous
21 321

322 SWITCHING EQUIPMENT FOR POWER CONTROL

converter substation. Like most switchboards for railway serv-
ice, there is only one D.C. polarity, the positive, brought to the
board, the negative and equalizer busses running between the
machines and not being located on the switchboard panel.

The ten panels near the right-hand end of the switchboard are
feeder panels having single-pole carbon break circuit breakers
connected to the main 600-volt bus at their upper stud, the lower
stud being connected to the top stud of the knife switch, and the
ammeter shunt being located in the strap connections between the
breaker and switch. The next six feeder panels are provided with
double-throw knife switches instead of single-throw, the lower
throw of these knife switches connecting to a transfer bus, this
transfer bus in turn being connected to the main bus through a
circuit breaker and switch. With this arrangement any of these
six feeder circuits can be operated either through its own circuit
breaker or through the circuit breaker on the transfer panel.

Beyond the feeder panels are D.C. load panels, panels for the
D.C. end of the converter, panels for the transformers feeding the
converter, and panels for the incoming A.C. line circuit.

On this particular switchboard where the panel sections are
20 inches, 45 inches and 25 inches, the upper sections of the D.C.
panels are reserved for the carbon circuit breakers, the middle
for the instruments and switches and the bottom sections of the
feeder panels are left blank. On the D.C. converter panels the bot-
tom sections contain watthour meters, while on the A.C. panels
these contain relays.

G. E. Power Switchboard. — Fig. 197 shows a typical Gene-
ral Electric double polarity 2- wire power station switchboard
controlling four generators and eight feeder circuits. With the
arrangement shown, the positive, negative and equalizer leads of
each generator are brought to the switchboard. The two
generator panels at right-hand end of switchboard each have a
three-pole switch, while the two at the left-hand end have each
three single-pole switches. The carbon breaker is in the positive
circuit of each generator. Each of the feeder circuits is provided
with a carbon breaker in the positive circuit and a knife switch in
the negative circuit.

With these three-section panels divided into sections 31 inches,
31 inches and 28 inches, the upper 31 inch sections are reserved
for circuit breaker and meter, while the middle section contains
the knife switches on the feeder circuits, and on the generator

LARGE PANEL SWITCHBOARDS

323

FIG. 197. — General Electric Co. three section switchboard.

FIG. 198. — Pittsburgh Electric Co. switchboard, front view.

324 SWITCHING EQUIPMENT FOR POWER CONTROL

circuits the field rheostat and voltmeter receptacle in addition to
the knife switches. Two D.C. voltmeters, located on a swinging
bracket, are placed at the end of the board.

Pittsburgh Electrical Power Board. — Fig. 198 shows a some what
similar D.C. switchboard built by the Pittsburgh Electric and Ma-
chine Works, utilizing Cutter (I.T.E.) circuit breakers, Weston
indicating meters, Sangamo watthour meters and knife switches

FIG. 199.

of their own design. This is a double polarity switchboard con-
trolling two 750-K.W. Synchronous converters and a smaller
unit as well as five outgoing feeder circuits.

Fig. 199 shows the rear view of this same switchboard illus-
trating the angle frame iron construction and the simplicity of
the bus bar arrangement due to the use of laminated stud circuit
breakers and switches.

This switchboard has its panels in three sections, 20 inches, 50
inches and 20 inches high, the top slab being reserved for the
carbon circuit breaker, the middle slab for the instruments and
switches, and the lower slab being left blank.

LARGE PANEL SWITCHBOARDS

325

Cutter 3 -wire Breakers. — For use with 3-wire D.C. gener-
ators that are provided with series fields in the positive and
negative circuits, a special arrangement of 4-pole carbon breaker
is furnished by the Cutter Company as shown in Fig. 200.

With this arrangement the main positive and main negative
circuits are run from the armature of the generator to the circuit-
breaker stud passing through the overload coil with a reversal
feature in one circuit, thence to the lower outside main stud, the

FIG. 200. — Cutter circuit breaker for three-wire generator.

leads being then brought back to the generator in order to pass
through the series fields in the positive and in the negative circuits.
The two outer poles of the circuit breaker connect to the positive
equalizer and the negative equalizer busses, while the two middle
poles connect to the positive main bus and the negative bus.
When the breaker operates through overload or reversal, all four
poles trip out at once, thus opening the positive, positive equa-
lizer, negative and negative equalizer circuits.

Electric Operation. — Where it is feasible to furnish an electri-
cally operated breaker located right at the machine, a 2-pole
breaker is frequently furnished for connecting in the armature
leads. Such a breaker completely opens up the generator arma-
ture circuit, but will normally leave the series coils connected

326 SWITCHING EQUIPMENT FOR POWER CONTROL

across between the positive and positive equalizer bus, the nega-
tive and the negative equalizer bus.

Neutral Lead. — With most 3-wire generators the neutral
lead is obtained from the neutral point of an auto transformer
or balance coil connected across two collector rings. This
neutral is normally grounded and frequently no switches what-
ever are furnished for use in the neutral circuit.

SPECIAL ISOLATED PLANT SWITCHBOARDS

In isolated plants, factories, or large office buildings the design
of the switchboard is frequently based on specifications issued by
the consulting engineer or architect, and these very seldom follow
out the designs that have been standardized by the larger manu-
facturing companies.

Such isolated plant switchboards as a rule control a com-
paratively large number of feeder circuits, and it becomes neces-
sary to control a number of feeders from each panel, such an
arrangement usually resulting in a special design of switchboard
for each individual case.

Walker Switchboard. — Fig. 201 shows a fine example of a
switchboard of this type built by the Walker Electric Company,
and installed in the plant of the Curtis Publishing Company, of
Philadelphia.

This switchboard utilizes Cutter circuit breakers, Weston
vertical edgewise group mounted feeder ammeters, Weston
flush mounted illuminated dial instruments and controls the
output of eight 2-wire, 250- volt generators and two 3-wire
balancers, the total generating capacity being approximately
3000 K.W.

An eight section control desk located in front of the switch-
board controls the generators and is provided with flush mounted
illuminated dial Weston ammeters and the control switches for
the electrically operated generator breakers, the motor operated
field rheostat, etc. The control desk as well as the panel board
is of gray marble.

The panel board is made up of one station panel, two balancer
panels, five lighting and six power panels. Each of these lighting
and power panels controls six circuits, so that there are a total
of 66-2- wire feeders controlled from this board, each equipped
with a 2-pole circuit breaker and an ammeter. Knife switches

LARGE PANEL SWITCHBOARDS

327

328 SWITCHING EQUIPMENT FOR POWER CONTROL

are entirely absent from the switchboard with the exception of
those required for the three wire balancers.

As the circuit breakers in the feeder circuits embody the non-
closable on overload feature, no switches are needed in series with
them.

Short Circuit Conditions. — For light and power service at 250
volts in plants of moderate capacity, particularly when fed from
D.C. generators in place of synchronous converters, the short-cir-
cuit conditions on the carbon breakers are not so severe, and the
resulting arc is not as intense as encountered in railway sub-
stations of large capacity operated from synchronous converters.

Carbon break circuit breakers can, therefore, be utilized to
advantage, placed one above the other on switchboard panels for
this class of service, whereas for railway work it becomes almost
essential to locate them at the top of a panel so that the resulting
arc cannot damage the panel and will have ample space in which
to extinguish itself.

Circuit-Breaker Protection. — Single bus railway panels pro-
vide automatic overload protection in one side of the circuit only;
namely, in the positive side, opposite the series field. This pro-
tection is sufficient for synchronous converters with overload
protection on the alternating-current side and for motor driven
generators with overload protection in the motor circuit.

Engine Generators. — There is a possibility in using this single
protection with engine driven railway generators having the nega-
tive lead grounded, that the circuit breaker in the positive side
does not protect the generator against possible damage due to a
ground either in the machine or on the positive side between the
machine and circuit breaker. An additional circuit breaker
mounted on a pedestal and installed in the negative armature
lead, is required by the National Board of Fire Underwriters.
This breaker, when provided, has an auxiliary switch, so that
upon the opening of the breaker, the switch will act in connection
with the low voltage release mechanism of the positive breaker
and cause it to open. It is recommended that the negative
breaker be set higher than the positive breaker on the switch-
board and thus permit the latter breaker to take care of the
ordinary overloads.

Converters & M.G. Sets. — Direct-current panels for synchron-
ous converters and motor generators, 2- wire or 3-wire D.C.
service, regularly include a reverse-current relay operated from

LARGE PANEL SWITCHBOARDS 329

the ammeter shunt, in addition to the low voltage release mech-
anism supplied with the direct-current circuit breaker. An
A.C. low voltage coil is supplied on converter panels and a D.C.
low voltage coil on generator panels. For 3-wire service one
reverse-current relay or attachment will be found sufficient
in all cases except when it is possible that battery charging may be
done, at times, from one side of the circuit only. In this case,
two reverse-current relays are necessary for absolute protection.

Two Wire. — Two-wire light and power panels provide auto-
matic overload protection in only one side of the circuit, namely,
in the positive side opposite the series field. This is approved
as sufficient protection by the National Board of Fire Under-
writers.

Three Wire. — Three- wire light and power panels are required
by the National Safety Code to operate with the neutral grounded.
They provide complete automatic overload protection on both
sides of the machine. Except with three wire booster converters,
which are shunt machines, a 2-pole carbon circuit breaker with
equalizer contacts is regularly furnished by the Westinghouse
Company for machines of guaranteed capacity of 2000 amperes
and below for one or more hours. For machines of larger
capacities a 4-pole breaker is regularly furnished consisting of
a positive and negative pole of capacity suitable for the ma-
chine, and two equalizer poles of approximately half the capacity
of the main poles. The Westinghouse breaker is tripped through
overload relays, operated from the ammeter shunts located on
the generators and connected in the circuit between the armature
and the equalizer leads.

Three wire booster converters have no compound windings and
their panels are furnished with an overload automatic 2-pole
carbon breaker. No overload relays are necesary, and the am-
meter shunts are mounted on the panel.

Panels controlling the direct-current side of a synchronous
converter or motor generator have the circuit breaker equipped
with a low voltage release mechanism having, an A.C. coil for
converters and a D.C. coil for generators, to open the breaker
by the operation of the speed limit device when furnished and to
provide means of tripping the direct-current breaker upon the
opening of the alternating-current breaker.

Meters. — Round pattern polarized ammeters and voltmeters
are regularly furnished with these panels. Illuminated dial

330 SWITCHING EQUIPMENT FOR POWER CONTROL

instruments may be substituted. The full scale of ammeters
corresponds approximately to the momentary overload guarantee
of the machine.

Reactive factor meters are supplied by the Westinghouse
Company with synchronous converter D.C. panels. They give
an emphatic indication of the idle component of the volt am-
peres. These instruments are single phase and will indicate the
reactive factor of one phase of the 6-phase synchronous con-
verter. As the phases are balanced, this is sufficient for all
operating conditions.

The General Electric Company furnish a reactive volt ampere
indicator reading reactive K.V.A. for the same service.

AC. Line

Am Shunt

Storting
Switch

Kheo

FIG. 202. — Diagram of D.C. starting of synchronous converters.

D.C. Starting. — When D.C. starting of motor driven generators
and synchronous converters is desired, the standard panels must
be modified. The purpose of these additions is shown in the
diagram, Fig. 202. The single-throw auxiliary switch is open
when the main switch is open. This switch opens the tripping
circuit of the reverse-current relay during starting, making it
impossible for the reverse-current relay to trip the alternating-
current breaker until synchronizing has been done and the direct-
current voltage adjusted, so that the machine when switched in
will operate in the normal direction. The auxiliary switch is
also in series with the auxiliary switch of the alternating-current

LARGE PANEL SWITCHBOARDS 331

automatic breaker and opens the interlock connection with the
direct-current breaker, so that the latter can be closed for
starting while the alternating-current breaker is in the open
position.

The equalizer switch is double throw to cut out the series field
in starting.

A.C. Panels. — The panels used for the control of the A.C. end
of synchronous converters and their transformers are usually
made to line up with the D.C. panels.

Protection. — Automatic protection on the alternating- current
side of the synchronous converter is provided on the high tension
side of the step down transformer by an instantaneous overload
oil circuit breaker, tripped from current transformers. The
breaker is also equipped with low voltage release and auxiliary
switch. A low voltage trip instantaneous overload carbon circuit
breaker is provided for the direct-current side. In the majority
of railway applications involving capacities of 1000 K.W. and
below it is advisable to eliminate the overload feature on the D.C.
breaker. The low voltage coil of the direct-current breaker is
connected to the low tension transformer leads in parallel with
the low voltage coil of the A.C. breaker. The speed-limit switch
furnished with and mounted on the converter, opens upon over-
speed and causes both A.C. and D.C. breakers to trip simultane-
ously.

The low voltage coil on the D.C. breaker is also actuated by an
auxiliary switch that is always provided on the oil circuit breaker
so that when this breaker opens, the direct-current breaker also
opens, thus providing against motoring from direct-current
power and eliminating the liability of reversal in polarity on
compound wound machines. Reverse-current relays are also
provided on the D.C. panel, arranged to open the alternating-
current breaker upon reversal of direct-current power, which in
turn opens the direct-current breaker. The reverse-current
relay may be omitted only if the converter is not interconnected
with an independent source of direct-current power, so that there
can be no reversal upon the interruption of the alternating-cur-
rent supply.

Transformers. — transformer primary circuit-breaker equip-
ments constitute part of the complete switchboard equipment
for the control of alternating-current self-starting synchronous
converters.

332 SWITCHING EQUIPMENT FOR POWER CONTROL

These equipments usually comprise one 3-pole, single-
throw instantaneous overload, automatic oil circuit breaker, of
one of the following types:

1. Hand operated, remote mechanically operated, instantane-
ous overload, automatic oil circuit breaker, complete with two
5-ampere trip coils, low voltage release mechanism coil and hand-
reset device and auxiliary contact to interlock with D.C. breaker.

2. Electrically operated 125-volt D.C. control, oil circuit
breaker, with two 5-ampere trip coils at breaker, instantaneous
overload.

In case inverse time element is desired with the breaker equip-
ment, two overload relays may be added to the electrically
operated circuit breaker. With the remote manually operated
oil circuit breakers only, inverse time element attachments
can be furnished with the circuit breaker.

Starting Panels. — These provide for the starting switch equip-
ment for alternating-current self -starting converters. They are
in addition to the converter panel.

The starting panels for th.e 600-volt converters often include
equalizer and negative switches. When the relative location of
the apparatus in the station is such that it is not desirable to
run the equalizer and negative cables to the starting panel, a
separate pedestal with proper equalizer and negative switches
may be used.

Starting Switch. — These starting panels usually have mounted
on them a 3-pole double-throw knife switch to connect the con-
verter to low voltage for starting and full voltage for running as
well as a 2-pole double-throw switch for field reversing in case
machine comes up to speed with the incorrect polarity.

When the synchronous converter is used for 3-wire D.C. service
an auxiliary blade is furnished on the starting switch and extra
contacts furnished so that in the running position the neutral of
the D.C. system is connected to the neutral point on the low
tension windings of the various transformers. Figure 203
shows the connections of a typical synchronous converter
installation for 3-wire D.C. service.

1500 Volt D.C.— Where the D.C. panels are intended for 1200-
1500-volt service, the carbon breakers and knife switches are
made distant control and the panels arranged as shown in Fig.
204. These panels are intended for use with two generators or
converters operating in series and each panel consists of three sec-

LARGE PANEL SWITCHBOARDS

333

3 Phase Incoming

Note' -Switchboard Conn- Line

ections ore shown as

Ground
'

FIG. 203. — Diagram of connections for D.C. three-wire.

334 SWITCHING EQUIPMENT FOR POWER CONTROL

tions 2 inches thick with 3^-inch bevels; the lower section is 25
inches high, the middle section 45 inches high, and the upper
section 30 inches high. They are mounted on angle iron frame
with channel iron base. The total height of the panel including
the base is 102 inches. The barriers provided between the circuit
breakers and at the ends extend 14 inches above the top of the
panel. No high voltage live parts are mounted within 7 feet of
the floor on the front of the panels.

The starting switch and the field discharge switch on the front

of the starting panels are pro-
vided with barriers to protect
against accidental contact
with live parts.

Meters. — The instruments
included with these panels in
the direct-current circuits
have live parts insulated from
the case for full voltage and
cases grounded.

Reactive factor meters or
power factor meters are sup-
plied for synchronous con-
verters as an aid in adjusting
the field properly to keep
down the losses in the ma-
chine armatures. These
losses are less, the more nearly

the synchronous converter operates at zero reactive factor.
The reactive factor meter is connected in the low voltage leads

to the converter and not on the high voltage side of the step down

transformers in order that it will indicate the true condition in

the converter armature.

Synchronous motor panels are supplied with a main ammeter

and a field ammeter for indicating proper machine operation.
Rheostats. — When two machines are connected in series for

1200-volt operation, their two rheostats are operated in tandem as

one circuit from a single hand wheel. An insulated sprocket wheel

is furnished on each rheostat so that the operating mechanism

is insulated from live parts.

Circuit Breakers. — The positive circuit breakers are mounted

on the front and at the top of the panels and are operated by

FIG. 204. — Switchboard for 1500-volt
D.C. railway.

LARGE PANEL SWITCHBOARDS

335

closing and tripping handles located at a convenient height on the
middle panel section. The circuit breakers trip free of the closing
mechanism so that the speed of opening is the same as for direct
operated breakers. The closing and tripping mechanisms are
insulated from the breaker.

Note -Switchboard Conn-
ections oresho»>n as
viewed Irotn rear of 6oonf

J Phase Incoming
Line

Supplied only on
Specifications

Commutotinq /
FIQ. 205. — Diagram of connections for 1500-volt D.C. railway.

The installation of negative machine circuit breakers is opti-
onal. They provide additional protection against grounds caused
by flash-over or insulation failure. In standard practice the
circuit breakers in the alternating-current supply circuits are
depended upon to provide this protection. The negative breakers
are direct-operated, being located at a convenient height on
pedestals. The moving parts of the negative breakers are dead
when the breakers are open.

Switches. — The positive switches are mounted on bases on the
rear of the panels, with Westinghouse construction, or on the

336 SWITCHING EQUIPMENT FOR POWER CONTROL

front top section alongside of the circuit breaker for General
Electric construction, the lowest point of live parts being at least
7 feet above the floor, and are operated from handles on the front,
located at a convenient height and in line with the circuit-breaker
handles. The operating mechanism is rigidly connected to the
switch so that the position of the handle on the front is always
a true indication whether the switches are open or closed.

Switches. — The switches for the negative side of the machine
set are direct-operated. These are of the 600- volt type and are
provided with barriers when connections are such that atten-
dants would otherwise be exposed to a dangerous voltage. Nega-
ive and equalizer apparatus may be omitted, if desired, when
the station will have but a 1200-volt converter or generator set,
as they are not essential for the operation of a single set. A nega-
tive main switch is convenient as a means of disconnecting the
machine from the ground for insulation testing.

Connections. — Fig. 205 shows the connections of a typical
substation for the control of a 13,200-volt 3-phase incoming
line and two 6-phase synchronous converters, self-starting from
the A.C. side and operating in series on the D.C. side for 1200-
1500- volts D.C. railway service.

AUTOMATIC SUBSTATIONS

For many synchronous converter substations, particularly for
interurban railway work, automatic operation has been adopted.
Very complete and ingenious arrangements of apparatus have
been worked out by the engineers of the General Electric Company
and the Westinghouse Electric & Manufacturing Company.
The first automatically controlled railway substation was
equipped by the General Electric Company and placed in service
during December, 1914, on the Elgin and Belvedere Electric
Railway. The following description has been taken from a paper
by Mr. Frank Peters, of the General Electric Company, presented
before the Pittsburgh Meeting of the A.I.E.E., March 14, 1920.

G. E. Schemes. — The type of automatic equipments supplied
by the General Electric Company consists of a group of relays,
grid resistors and standard contactors, which together with a
motor driven drum controller perform the usual function of
starting, stopping and protecting the machines against irregu-
larities without the aid of an attendant. In general, relays are

LARGE PANEL SWITCHBOARDS

337

used where the functions of starting, stopping and protecting the
machines depend upon voltage, current or independent time
values. During starting and stopping, however, numerous opera-
tions must be performed in a definite sequence, which if not
strictly adhered to, is conducive to service interruptions.

Controller. — The motor driven drum controller is used to ob-
tain this fixed time relation of events and to substitute, wherever
possible, a type of contact more substantial than can be used with

FIG. 206. — General Electric Co. motor driven controller for automatic sub-
station.

relays. This device also includes a small D.C. generator which
at the proper time during the starting operation separately ex-
cites the converter field, thereby definitely and immediately in-
suring the correct polarity.

Duties. — Protective devices having the following duties are
provided to perform the functions ordinarily left to the discre-
tion of the operator.

1. To limit the overloads.

2. To limit the temperatures.

3. To shut down the machine.

(a) When A.C. or continuous D.C. short circuits occur.
(6) Upon failure of alternating current.

(d) In case of excessive speed.

(e) Upon reversal of direct current.

4. To prevent machine starting.

(a) During low A.C. voltage.

(b) During single-phase A.C. supply.

Connections. — By referring to Fig. 207 which is a typical
wiring diagram of an automatic 500-K.W. 600- volt equipment, the

338 SWITCHING EQUIPMENT FOR POWER CONTROL

-i!

LARGE PANEL SWITCHBOARDS 339

sequence of operation may be followed. For convenience of
reference the principal devices have been numbered or otherwise
labeled. It will be noted that the 220-volt A.C. control bus is
continuously excited from the control transformer No. 1 1 and the
operating coil of contact-making voltmeter No. 1 is always
connected between trolley and ground.

Starting. — Assuming a particular station is shut down and a
train is approaching. As it increases its distance from the next
station on the line it will eventually cause the trolley voltage to
drop and at a predetermined value, usually 450 volts, contact-
making voltmeter No. 1 opens, de-energizing the operating coil
of relay No. 2, which had been previously held open by excita-
tion from the 220-volt A.C. control bus through relay No. 1.
The closing of No. 2 closes relay No. 3 causing it to pick up and
close contactor No. 4 provided the hand reset switch and contacts
of A.C. low voltage relays No. 27 are closed. Relay No. 2 has
a dashpot to prevent momentary fluctuation of low voltage from
producing false operations of the machine. With the drum
controller No. 34 in the "off" position as would be the case before
the machine starts, contactor No. 4 completes a circuit through
segments No. 13 and No. 16 on the drum controller and the
limit switch of the brush-raising device which closes contactor
No. 6, thereby starting rotation of the motor driven drum con-
troller. Controller segment No. 15 soon closes contactor No. 5
which in turn energizes the motor operated oil switch mechanism
causing the main converter transformers to become energized by
the closing of oil circuit breaker No. 7. The operating coil con-
nection of contactor No. 5 is then transferred from segment No.
15 to No. 14. This circuit passes through an auxiliary switch on
the oil circuit breaker to insure the return of all devices to their
normal position should the breaker open for any reason. When
segment No. 2 makes contact, starting contactor No. 10 is closed
connecting the converter to the low voltage taps provided the
A.C. supply is delivering 3-phase current as determined by
relay No. 32. Shortly the drum controller stops rotating be-
cause of the gap in segment No. 16 and waits if necessary for the
converter to come up to speed. At approximately synchronism,
speed-control switch No. 13 closes, bridging by aid of segment
No. 20 the gap in segment No. 16, causing the controller again to
start rotating so as to complete the function of connecting the
machine to the line.

340 SWITCHING EQUIPMENT FOR POWER CONTROL

Next segment No. 3 closes contactor No. 31 connecting to the
converter fields a 250-volt supply obtained from the small gen-
erator on the drum controller, thereby immediately ensuring proper
polarity. Contactor .No. 31 is then opened by segment No. 3
and the self-exciting field contactor No. 14 closed by segment No.
4 and running contactor No. 16 closed by segment No. 5
connecting the converter to normal secondary A.C. voltage.
Starting and running contactors No. 10 and No. 16 are both mechan-
rically and electrically interlocked with respect to one another
to insure against accidentally short-circuiting a portion of the trans-
former secondary winding. Segment No. 26 next starts the
motor operated brush rigging causing the converter brushes to
be lowered, which completes the operation of preparing the ma-
chine for connection to the D.C. bus. Segment No. 7 is next
energized with 600 volts direct current and shortly thereafter
segment No. 8 closes the D.C. line contactor No. 18 whose con-
trol circuit is in series with converter field relay No. 30, polarized
relay No. 36 and auxiliary switches on running contactor No.
16 and control contactor No. 4, thereby ensuring before closing
No. 18 that the converter has proper polarity, correct field and
full voltage A.C. running connections.

As soon as the line contactor closes the machine delivers load
to the bus through the load limiting resistors which, however,
are soon short-circuited by contactors No. 20 and No. 21 opera-
ted by segments No. 9 and No. 10. The drum controller is then
stopped by segment No. 17. When connection to the bus is
made through No. 18 the flow of current closes relay No. 37,
which will cause relay No. 3 to remain closed regardless of relay
No. 1 whose function started the station. In other words the con-
trol of the station is now dependent on the contacts of No. 37
which will remain closed so long as a predetermined current is
being delivered to the bus. Should the current fall below a set
value, relay No. 37 will open and cause relay No. 3 to drop out
after a certain period of time and shut down the station. Relay
No. 3 has a dashpot and is timed so that momentary low values
of current causing No. 37 to open will not shut down the equip-
ment.

Shutting Down. — When the station does shut down, relay No.
3 opens contactor No. 4 causing running contactor No. 16 and
D.C. line contactor No. 18 to drop out and disconnect the ma-
chine. Contactor No. 5 opens after contactor No. 4 which

LARGE PANEL SWITCHBOARDS 341

operation establishes through an auxiliary contact a circuit to
contactor No. 6, thereby starting the controller and running it
to its "off" position. While doing this, however, segment No.
24 trips out the oil circuit breaker and segment No. 25 causes
the converter brushes to be raised in preparation for starting
upon the next load demand.

Overload. — In the event a heavy D.C. overload occurs, relay
No. 24 will pick up and open contactor No. 20, thereby inserting
resistance in the circuit. Should the overload increase to a
greater value, relay No. 25 will operate and insert more resist-
ance, and in stations not provided with individual feeder pro-
tection a third step of resistance is provided to limit still greater
overload demands. The value of resistance used is such as to
permit short circuit in the immediate vicinity of the station with-
out injuring the machine. In some stations individual feeder
protection, which consists of an overload relay No. 23, a contactor
No. 19 and a resistor in each feeder circuit, is installed, there-
by localizing to a degree the function of overload protection to
each feeder. With such an arrangement only two sections of
resistance are used in the machine circuit.

Overheating. — Protection from overheating the machine, its
bearings and load limiting resistors is obtained by use of tempera-
ture relays No. 38 and No. 33 arranged to shut down the station
immediately should such a condition arise.

Reversal. — A reversal of direct current is prevented by relay
No. 29 and overspeed by speed-limit switch No. 12-A. Both
of these devices necessarily operate a control circuit which im-
mediately opens contactor No. 4 and shuts down the station.
A shunt trip hand operated D.C. circuit breaker No. 15 is in
series with No. 18 and only used to protect against the possi-
bility of the line contactor freezing closed. Should this condi-
tion occur the converter would motor from the D.C. end upon
the A.C. end being disconnected and the excessive speed result-
ing would trip the circuit breaker No. 15 through the operation
of speed switch No. 12.

Short Circuit. — In case a short circuit occurs on the A.C. side
of the equipment, the definite time limit overload relay No. 28
will trip out the main oil circuit breaker, shutting down the
station and at the same time opening the hand reset switch which
necessitates reclosing by hand before the station can be started

342 SWITCHING EQUIPMENT FOR POWER CONTROL

again. This feature insures an inspector visiting the station
to investigate the cause of the serious A.C. overload.

Low A.C. voltage relay No. 27 which is calibrated for a definite
value, is connected so as not to permit the station to start, or to
shut it down if running, should the high tension voltage become
so low as to interfere with proper operation.

If for any reason a single-phase condition exists on the second-
ary side of the transformer during starting operations, relay No.

FIG. 208. — General Electric Co. automatic substation with M.G. set.

32 will lock out starting contactor No. 10 and prevent the con-
verter from being connected to the transformer.

Polarized relay No. 36 protects against the possibility of the
machine ever being connected to the line in the reverse direction.
Unless proper polarity has been established before connecting
the machine to the bus, line contactor No. 18 will not close.

Motor Generator. — In stations containing a motor-generator
set instead of a synchronous converter, certain modifications to
the equipment are necessary to accommodate the starting opera-
tions, but the scheme of operation with few exceptions is similar
to the converter equipments. Oil immersed starting and running
contactors are used because of the higher transformer secondary

LARGE PANEL SWITCHBOARDS 343

voltage and a certain amount of overload protection is obtained
by inserting one or two steps of resistance in the generator field
circuit in addition to two steps of series resistance in the main
D.C. circuit. This arrangement reduces initial cost since the field
resistance and its contactors are of small capacity. An energy
saving in resistor heat loss is also accomplished. The 250- volt
generator on the drum controller becomes unnecessary in the
case of a motor generator automatic equipment. See Fig. 208
for automatic substation with motor-generator set.

Westinghouse Schemes. — The automatic substation equip-
ment of the Westinghouse Electric & Manufacturing Company
has been designed to duplicate in every way the manual operation
of substation apparatus without the attention of an operator.
Starting and shutting down of the station are functions of the
load demand. In addition, many protective devices uncommon
to the average substation give absolute protection which is free
from the human element. The schematic diagram Fig. 209
applies to equipment for standard alternating-current, self-
starting synchronous converters up to and including 1500-
kilowatt capacity, 750-volts direct-current. Referring to this
diagram, the scheme of operation is as follows:

Starting. — A car or train enters the zone of a station which is
at that instant idle. As the train approaches the station, the
trolley voltage at the station is reduced. When the voltage
falls to a predetermined value, for example to 75 per cent, of
normal or below, contacts of a direct-current voltage relay (1)
in the trolley circuit close, and as a result the coil of an alternating-
current voltage relay (2) is energized, through an interlock on the
brush lifting device (31), closed when brushes are raised from
commutator. At the end of a definite time interval, which may
be adjusted from instantaneous to five seconds, the contacts of
this relay close. The time element prevents the station re-
sponding to momentary reductions in D.C. voltage, and in
addition prevents the station from starting in case the A.C.
voltage is abnormally low. The closed contacts of A.C.voltage
relay (2) complete a circuit which closes the master relay (3)
thereby energizing an auxiliary control bus 'A-2'. Relay (3)
completes its own holding circuit, making further functioning
of the control apparatus independent of trolley voltage.

Energizing of auxiliary control bus 'A-2' causes oil breaker
(20) to close through the functioning of its control contactor (22).

344 SWITCHING EQUIPMENT FOR POWER CONTROL

The oil breaker in the closed position completes, through an
interlock, the circuit for an alternating-current dashpot relay
(21) which, when closed, de-energizes the oil breaker control

... .

SjftSiat 23 AC' Onload Relay,
24 Overspeed Devree

GridThrrrna iConv'rt'r) 40-80 Feeder Contacton

mal Kolay 41-81 DC Feeder Resisfnoe
Lock-Out Relay Shunting Contacton

FIG. 209. — Diagram of connections Westinghouse automatic substation.

contactor (22). The oil breaker latches closed mechanically.
In addition, bus 'A-2' energized, closes shunt relay (4) and
field contactor (5). The closing of relay (4) in turn closes alter-
nating-current machine starting contactor (6) which connects

LARGE PANEL SWITCHBOARDS

345

the converter to the starting taps of the power transformers. It
will be noted that the closing of relay (4) and contactor (5)
also completes the circuit for a polarized motor which drives a
rotary switch (7) upon which is mounted four pairs of contacts,
(7a), (7b), (7c) and (7d).

Rotary switch (7) is driven by a D.C. motor having a perma-
nent magnet field in addition to the ordinary field winding. In
starting, field coils of the
motor are connected to
trolley and rail, and the
armature is connected to
the D.C. brushes of the
converter. Until the con-
verter pulls into step,
alternating current is de-
livered to the motor arma-
ture causing it to oscillate;
when the converter is in
step, direct current is de-
livered to the armature
causing it to rotate in a
direction dependent on the
polarity of the converter.
See Fig. 210.

Polarity. — Assuming incorrect polarity, the drum of (7) re-
volves in a counter clockwise direction. Relay (8) closes as
contact (7a) is made, completes its own holding circuit and closes
a contact in series with the coil of a direct-current relay (9) which
closes when contact is made at (7d). This relay completes its
own holding circuit, opens shunt field contactor (5) and closes
reverse field contactor (10). Relay (8) is opened by the shorting
of its coil, by an interlock closed when reverse field contactor (10)
is closed, thus permitting the rotary switch to idle over the
remaining contacts. The converter voltage on reverse field falls
to zero thereby de-energizing direct-current relay (9) which in
the open position causes reverse field contactor (10) to open, and
normal field contactor (5) to again close. This operation cor-
rects polarity under normal line conditions; however, should
reverse polarity persist, the above operation will be once or twice
repeated as may be necessary. In extreme cases, it is very
difficult to correct polarity by field reversal, so, should the third

FIG. 210. — Westinghouse rotary drum
switch for automatic substation.

346 SWITCHING EQUIPMENT FOR POWER CONTROL

attempt fail, relay (4) and in turn starting contactor (6) will be
opened by the closing of the contacts of the field reversal limiting
relay (26). This relay is a step by step device which operates
each time the direct-current relay (9) closes, but is mechanically
restored to first position when alternating-current starting con-
tactor (6) opens. The alternating-current starting contactor (6)
remains open for a short interval dependent on the time element
of an air dashpot which at the end of its travel trips open the
contacts of (26). Relay (4) now closes, in turn reclosing alter-
nating-current starting contactor (6). One familiar with sub-
station operation will appreciate that the above procedure
automatically duplicates the work of an operator correcting for
reversed polarity.

Assuming correct polarity, drum switch (7) rotates in a clock-
wise direction. Relay (8) closes as contact is made at (7a),
completes its own holding circuit and closes contacts in series
with shunt relay (19) which closes when contact is made at (7b).
Relay (19) closed, forms its own holding circuit, opens relay (4)
which in turn opens alternating-current contactor (6). The
closing of relay (19) and the opening of contactor (6) closes alter-
nating-current running contactor (11) thereby connecting the
converter with correct polarity to the full voltage A.C. circuit.
Interlocks opened by the closing of (11) de-energize the polarized
motor relay (7).

The alternating-current running contactor (11) in the closed
position, through the closing of an interlock, energizes the brush
lifting device (31) by which the direct-current brushes are
lowered into position on the converter commutator. An inter-
lock on (31), closed when brushes are in the running position,
completes, through an interlock on the alternating-current run-
ning contactor (11), a circuit which closes the direct-current line
switch (12) thus connecting the converter to the trolley through
resistance proportioned to limit the current in the machine to
approximately 150 per cent, of its rated full-load capacity. Re-
sistance shunting contactors (14) and (15) are closed by the direct-
current accelerating relays (12a) and (14a) should normal load
not be exceeded.

Feeders. — Feeder contactors (40)-(80) are normally closed,
the operating coils being energized from the trolley circuit.
Feeder resistance shunting contactors (80)-(81) open and close
dependent on current setting of D.C. series relays (40a)-(

LARGE PANEL SWITCHBOARDS 347

Assuming overload on feeder (41), series relay (40a) will open
contactor (41) thereby inserting resistance in series with the
feeder. Should the overload be severe and last for some length
of time, heat from the series resistance will open the contacts of
thermostat (33) thus opening contactor (40), thereby isolating
the feeder until the resistance cools to a point which will allow the
contacts of thermostat (33) to again close. If the sum of the
feeder loads through resistances is in excess of the safe load of the
converter, resistance shunting contactors (14) and (15) also open
through similar action of (12a) and (14a).

When all resistance is cut out of the circuit, the trolley voltage
at the station rises to a point which will open the contacts of
voltage relay (1). However, since the master relay (3) maintains
its own holding circuit, no action results from fluctuations of the
direct-current voltage.

Shutting Down. — Shutting down of the station is dependent
on the position of series underload relay (13). When the load
on the converter falls to or below a predetermined value, the
contacts of this relay close, thereby starting the underload delay
relay (27).

Relays. — Underload delay relay (27) consists of a direct-cur-
rent motor driving, through a train of gears and a magnetic
clutch, a vertical shaft mounting a small arm which, at the end
of its travel, closes a pair of contacts short-circuiting the coil of
the master relay (3), causing it to drop out, thus de-energizing
the auxiliary control bus 'A-2' and thereby opening all alter-
nating-current and direct-current contactors. The master relay
in the open position closes an interlock which energizes the
brush lifting device (31) and the brushes are raised from the
commutator to the starting position. Should load be de-
manded from the station before the contacts of underload delay
relay (27) are closed, the opening of the contacts of series relay
(13) de-energizes the motor and magnetic clutch in series with it.
The shaft releases and is returned to its starting position by
means of a small coiled spring, thus assuring a very definite
no-load period. Any time element desired between the limits
of 3-and 30-minutes may be secured by simple adjustments.

Reverse-phase starting and single-phase starting are prevented
by the closing of the contacts of reverse phase and low voltage
relay (18) which short-circuits the coil of the master relay (3).

Low Voltage. — If the alternating current line voltage is too

348 SWITCHING EQUIPMENT FOR POWER CONTROL

low for satisfactory operation, relay (2) will not operate and the
contacts of relay (18) close, as stated in the above paragraph,
either of which prevents the station from starting. Should low
voltage occur while the station is in operation, the contacts of
relay (18) close.

Direct-Current Overload. — Various sections of the current
limiting resistor are inserted in the machine circuits by con-
tactors (14) and (15), when loads exceed the setting of the over-
load trip on the contactors. When the current values are within
the overload setting of the contactors, they again reclose.
Overload settings of the switches and the ohmic value of the re-
sistor sections are dependent upon the particular application.

Temperature. — Thermostats are placed in the machine bear-
ings and in each resistor section. Should an overload persist
to the extent of overheating a section of the resistor, or should
a machine bearing reach a dangerous temperature, the station
will be shut down by the short-circuiting of the coil of master
relay (3). When the resistor temperature returns to normal
the station comes back on the line, unless prevented by the
setting of lockout relay (30). However, the station once shut
down due to an overheated bearing can only be restored to serv-
ice by resetting the thermostat contacts by hand.

In order to take the maximum advantage of the overload
capacity of the synchronous converter, the current limiting
devices are usually set to correspond to the momentary overload
rating, while a Replica Thermal Relay protects against sustained
or repeated overloads. This device is essentially a thermostat
having a temperature characteristic similar to that of the machine
which it protects and is heated by a current proportional to
that in the converter armature. As the armature conductors
approach a dangerous temperature, the thermostat contacts close,
shunting the coil of master relay (3), thereby shutting down the
station until the apparatus has cooled.

Alternating-Current Overload. — Should trouble develop be-
tween the high tension side of the power transformers and the
direct-current limiting resistor, protection is obtained by the
operation of alternating-current overload relays (23) which
short-circuit the coil of master relay (3) thereby shutting down
the station.

Polarity. — The fact that the polarized motor relay (7) must
rotate in a clockwise direction, in order to establish the proper

LARGE PANEL SWITCHBOARDS 349

sequence of operations, insures the machines coming onto the
line with correct polarity.

Reverse Current.— The equipment includes the usual direct-
current reverse-current relay (32) which, when the contacts are
closed, short-circuits the coil of master relay (3) thus shutting
down the station.

Overspeed. — The usual speed limit device (24) mounted on
the converter, furnishes protection from overspeed by opening
master relay (3).

FIG. 211. — Westinghouse automatic substation

Thermostat. — Liquid thermostats of the copper bellows
type are placed in the machine bearings and in each resistor
section. The converter bearings are so arranged that the operat-
ing element of the thermostats is embedded in the bearing shell.
Thermostats of this type are very rugged and operate very
satisfactorily throughout wide ranges of temperature.

Lockout Feature. — This feature is provided by a notch up
relay (30) which operates each time the main oil switch closes
and is reset to zero position by the closing direct-current contac-
tor (15). If the oil breaker closes three times before the direct-
current contactor (15) is closed, the contacts of relay (30) close,
short-circuiting the coil of the master relay (3) thus locking out

350 SWITCHING EQUIPMENT FOR POWER CONTROL

the station until the trouble has been remedied and relay(30)
reset by hand.

Continuous Running. — If the 2-pole double-throw switch
(17) is thrown to the right, the underload delay relay (27) is
out of circuit and the station will start and run continuously
but with all automatic protective features. A typical automatic
substation arrangement is shown in Fig. 211.

PORTABLE SUBSTATIONS

In connection with many railway systems employing synchron-
ous converters it is frequently advisable to have a synchronous

High Tension Met

Plan View

DC Outlet

Sectional Elevation

FIG. 212. — Sectional view of portable substation.

converter with its transformer and switchboard equipment placed
in a suitable car so that it can be moved from one part of the
system to another wherever there is an extra demand for current
that cannot be taken care of by the nearest substation. Owing
to the low head room in a car and the necessity for compact

LARGE PANEL SWITCHBOARDS 351

and simple equipment, the standard synchronous converter equip-
ment has been modified utilizing small panels but providing all
necessary control and metering equipment except that for the
high voltage side of the step down transformers.

They are designed for 300-K.W. and 500-K.W. 25-cycle and
60-cycle, 6-phase synchronous converters, which are self-starting
from the alternating-current side.

The panels are 1% inches thick with %-inch bevels, mounted
on angle iron framework extended for bracing to the roof of the
car.

The circuit breaker, knife switch, and instrument equipment
for the low voltage alternating-current and the direct-current sides
of the converter is the same as previously outlined, except that the
alternating-current starting knife switch is hand operated, re-
mote control, for mounting under the car.

Air-break switches having low voltage trip and fuses are used
for protecting the step down transformers and the converter.
The switch is operated from a handle on the panel and is inter-
locked electrically with the direct-current circuit breaker so
that the latter is opened when the former trips. Fig. 212 shows
a sectional view of a portable substation.

ELECTRICALLY OPERATED D.C. SWITCHBOARDS

Field & Exciter. — While electrical operation is fairly common
for high voltage A.C. boards using oil circuit breakers it is not
used so frequently for D.C. or low voltage A.C. with carbon
breakers but there are some cases where it is also used to ad-
vantage for low tension A.C. or D.C. service using carbon cir-
cuit breakers. Probably the place where electrical operation is
used most frequently for D.C. service is for the control of ex-
citers and field circuits in a generating station where electrical
control is employed for the main A.C. circuits and the exciter and
field circuits are electrically controlled from the generator switch-
board.

Rio de Janeiro. — Where the distance from the switchboard to
the field switches and field rheostats is great, it frequently be-
comes advisable to operate these devices electrically. These
are frequently combined to form a switchboard like that shown
in Fig. 213 which was supplied by the Westinghouse Electric and
Manufacturing Company to control the field circuits of six 5000-

352 SWITCHING EQUIPMENT FOR POWER CONTROL

K.V.A. generators and the field and armature circuits of three
200-K.W. 250-volt exciters. Each exciter is provided with two
800-ampere, 3-pole, solenoid operated carbon breakers for connect-
ing to either or both of two sets of direct-current bus bars, one of
which is used for light and power service, and the other for
excitation. The generator panels are provided with 2-pole, sole-
noid operated field switches and motor operated field rheostats.

FIG. 213. — Field & exciter switchboard for Rio de Janeiro.

Rheostats. — The motor operated field rheostat faceplate used
in this plant is provided with a clutch, so that in case of trouble
to the motor the faceplate may be operated by hand after dis-
engaging the clutch. With this faceplate a signal switch is pro-
vided to actuate a lamp on the switchboard when the arm is
bridging two contacts. This faceplate is also provided with a
limit switch that opens up the motor circuit when the arm has
reached the limit of its travel in either direction, and the connec-
tions are so made that while the motor can no longer be operated
in one direction it can be run in the opposite direction.

Inawashiro. — In certain cases it is preferable to mount the
electrically operated field rheostats entirely independent of the
field switchboard which is then reserved exclusively for the ex-
citer breakers and the generator field switch equipment as shown
in Fig. 214, which shows the exciter and field switchboard fur-
nished by the Westinghouse Company for the Inawashiro Hydro
Electric Company of Japan, for the control of four 200-K.W. 250
volt exciters and the field circuits of the six 7700-K. V. A. generators.

LARGE PANEL SWITCHBOARDS

353

This switchboard comprises six panels of marine finished slate
mounted on a self-supporting pipe framework with the back of
the board completely enclosed by an open mesh grill with locked
doors at each end.

The two panels for the field circuits of the generators each
contain six 2-pole solenoid operated field discharge switches used
in pairs for connecting the field circuits of three generators to
either of the two sets of field bus bars. These field switches are
electrically interlocked in pairs in such a way that only one of a
pair can be closed at a time.

FIG. 214. — Field & exciter switchboard for Inawashiro.

The four remaining panels which control the armature circuits
of the exciters each contain two 2-pole solenoid operated carbon
break circuit breakers provided with overload and reverse-current
definite time limit relays so arranged that any exciter can be
connected to either of the two sets of busses and the breakers are
interlocked so that the exciter can only be connected to one bus
at a time.

HEAVY D.C. ELECTRICALLY OPERATED BOARDS

Aluminum Company of America. — As an example of electrical
control applied to heavy capacity low voltage service, Fig. 215
shows the interior of the Marysville station of the Aluminum
Company of America containing nine 2500-K.W. 550- volt rotary
converters. The control desk may be noticed in the rear of the

354 SWITCHING EQUIPMENT FOR POWER CONTROL

station on the switchboard gallery and this contains the necessary
controllers and meters for the various circuits.

One of the nine synchronous converters is a spare while the re-
maining eight are operated in two groups of four each in parallel
on the D.C. end and on the A.C. end are fed from four sets of
secondary leads from the same transformer bank. The low ten-
sion A.C. leads are brought in from the transformers through the
right-hand wall. Three of the six phases run direct to the synch-

FIG. 215. — Marysville station of Aluminum Co. of America.

ronous convetrers while the remaining three pass through the 2500
amperes 3-pole solenoid operated carbon breaker near the right
hand-wall. The synchronous converters are started from the
D. C. end and synchronized before being thrown in on the A.C.
end. For starting after a complete shut down an A.C. starting
motor is provided for starting either of two synchronous converters
these in turn furnish the direct current for starting the others.
The spare rotary can be operated from any of the windings of
either of the two transformer banks in place of a rotary that is
out of commission and there is a spare transformer that can be
used in place of any of the six regular transformers.

LARGE PANEL SWITCHBOARDS 355

For the D.C. end of each rotary twc 5000-ampcre solenoid
operated carbon breakers are furnished and a 20,000-ampere
breaker is supplied in the outgoing feeder fed from four synch-
ronous converters in parallel.

G. E. Installations. — A number of large electrically operated
carbon break circuit-breaker outfits were supplied by the Gen-
eral Electric Company for the substations of the Interborough
and Metropolitan System in New York City and to other plants
in different places.

There are also numerous installations of electrically operated
carbon circuit breakers furnished by other builders for steel mill
service and large industrial plants.

I. T. E.-Ford Plant. — One of the most interesting installations
of I. T .E . circuit breakers, both hand and electrically operated
in a very large capacity, direct-current installation, is at the plant
of the Ford Motor Company, in Detroit, where there are fourteen
3750-K.W., one 2500-K.W. and one 1000-K.W. 250-volt D.C.

356 SWITCHING EQUIPMENT FOR POWER CONTROL

generators connecting to two 250-volt D.C. busses and supplying
energy to a large number of D.C. feeders.

Main Control Board. — A partial view of the main switch-
board showing the generator control panels is given in Fig. 216.
The panel at the extreme right-hand end contains graphic
instruments, the next two panels gyrostatic voltage balance
detectors, the next panels being generator control panels with
flush mounted illuminated dial Weston ammeters, Sangamo
watt-hour meters and special control switches used with the
generator breakers, signals, etc. Then there are more panels
with gyrostatic balancers, graphic meters, control circuits, etc.
The other end of the switchboard controls D.C feeders with 2-
pole carbon breakers at the top, round pattern flush mounted
Weston ammeters, and 2-pole double-throw knife switches so
arranged that the feeders can be connected to either of the two
sets of bus bars. On the gallery above are located additional
feeder panels.

Signals. — To facilitate the operation of the plant by the
switchboard attendant, a complete system of signals is provided
between each engine and the control section of the switchboard.
On the signal board is mounted an ammeter indicating the
generator current, two voltmeters showing the voltage on the
respective sides of the 3-wire ignition circuit, a switch for
completing the ignition circuit independent of the auxiliary switch
associated with the generator circuit breaker, and four signalling
switches. With each switch is associated a signal lamp having a
distinctively colored bull's eye lens. At the switchboard is
installed an identical set of lamps so that the signal given by the
engineer lights the corresponding lamp at the signal board as
well as the switchboard, and at the latter point a bell is also
rung in order to insure the prompt attention of the operator.

Circuit Breakers. — Those controlling the respective generators
are of the type shown in Fig. 217, these being triple-pole double-
throw controlling the positive, negative and equalizer leads and
providing alternative connections with either of the two sets of
busses. They are equipped with direct-acting overload time
limit features in each main lead, and with reverse-current trip in
the negative lead, thus insuring the generators against short
circuit or unduly sustained overloads and also against motoring.

Mechanism. — The remote control mechanisms are operated by
means of motors, there being one of these mechanisms for each

LARGE PANEL SWITCHBOARDS

357

pole. Directly associated with these are interlocking devices so
arranged that the poles of the circuit breaker may be closed only
in predetermined sequence; i.e., equalizer first, then positive and
finally the negative pole. When the circuit breaker is in the full
open position, positive and negative switch members of both
throws are locked out, and only the equalizer members are free

FIG. 217.

to be moved to the closed position. Whichever throw of the
equalizer is closed, the other is thereupon locked open, while
the positive pole which corresponds with the closed equalizer
pole is at the same time unlocked. The subsequent closing of
this member unlocks the corresponding negative pole. The
interlocks above referred to are mechanical and are effective
whether the apparatus is operated electrically or by hand.

Synchronous Converter Starting. — Another rather special
arrangement of motor operated double-throw carbon break circuit

358 SWITCHING EQUIPMENT FOR POWER CONTROL

breaker is shown in Fig. 218, this illustrating the starting and
running switch for use with a 2000-K. W. booster converter. This
starting switch consists of a 3-pole, two step arrangement for the
purpose of applying first, low voltage, and then full voltage to the
alternating-current end of the rotary. The three upper poles

FIG. 218.

which operate as a unit, carry the starting current which is sup-
plied at 93 volts, 60 cycles and reaches 9250 amperes as a maxi-
mum. These poles are amply capable of rupturing this current
in the event of failure of the synchronous converters to start.
The three lower poles which also operate as a unit carry the run-
ning current which may attain a maximum of 5500 amperes, the
voltage being 193.

LARGE PANEL SWITCHBOARDS 359

Both starting and running elements of the switch are arranged
for either hand or remote control and the two elements are so
interlocked both mechanically and electrically as to insure proper
sequence of operation under any and all conditions. The con-
struction is such that it is impossible to close the starting switch
unless the running switch is opened. The preliminary movement
of the running switch for the closed position causes the immediate
opening of the starting switch so that the arc on this switch is
broken before the circuit is established for the running switch.

As further protection against the improper application of full
potential to the synchronous converters an induction relay is pro-
vided which locks the running switch in the open position until the
rotary is running at very near synchronism. This induction relay
is so sensitive in its operation that it may readily be adapted
to release the running switch only when the synchronous converters
is half cycle or less per second out of synchronism.

CHAPTER XIV
HAND OPERATED A.C. SWITCHBOARDS

EXCITER PANELS

As practically all A.C. switchboards have to take care of the
exciters as well as the A.C. generators and the feeder circuits,
the exciter panels can really be considered as part of an A.C.
switchboard and are made to line up in general arrangement with
the A.C. board. The panels for the control of the exciters used
with alternating-current generators are essentially the same as
other 2-wire direct-current generator panels except that no
automatic protection is provided. Panels are suitable for
generator voltage regulators, either with or without control for
motor driven exciters. They are designed to match and form
part of the standard alternating-current switchboards.

Limits. — The capacity of a single exciter circuit is usually
limited to 300 amperes for the 48-inch panels and 1600 amperes
for the 90-inch panels.

Protection. — Standard practice in supplying switchboard
apparatus for control of exciter circuits is to furnish non-auto-
matic switching devices. Where the exciters are driven by
alternating-current motors, the automatic circuit breaker in the
motor supply will be furnished with a high overload setting.

This practice is in harmony with the Rules and Require-
ments of the National Electrical Code and is justified both be-
cause contrary practice would jeopardize the continuity of the
alternating-current service, and because modern exciting apparatus
is very reliable.

However, if special conditions make it necessary to provide
automatic protection in an exciter circuit, the builders are pre-
pared to supply suitable devices even though at variance with
their usual recommendations and practice.

Field Discharge. — It should be noted that any device to open
a live field circuit must be provided with a field discharge resist-
ance, as otherwise the opening of such a circuit may induce a
voltage in the field windings tending to puncture the insulation.

HAND OPERATED A.C. SWITCHBOARDS

361

In some cases with parallel-operated exciters it may be desir-
able to provide automatic devices that operate only on reversal of
energy in an exciter circuit, in order to disconnect a defective
exciter. In such cases standard generator panels having auto-
matic circuit breakers may be used by omitting the overload
feature on the breakers and adding the necessary reverse-current
devices.

Connections. — Fig. 219 shows typical connections for a steam
driven exciter, a motor operated exciter, a voltage regulator and

Fio. 219. — Typical connection exciter and field connections.

the field circuits of two generators. The usual equipment for
an exciter comprises a 3-pole switch or a 2-pole main switch
and a single-pole equalizer switch with an ammeter, a voltmeter
switch and a field rheostat for the main exciter circuit as well as
one for use with the exciter voltage regulator. One voltmeter
takes care of two or more exciters.

A.C. SWITCHBOARDS WITH KNIFE SWITCHES

For moderate voltage installations in industrial plants and
small central and distributing stations where voltages do not
exceed 480 volts, panels with knife switches and enclosed fuses
can be used where the cost of a switchboard with oil circuit

362 SWITCHING EQUIPMENT FOR POWER CONTROL

breakers is not justified. Enclosed fuses must not be supplied
under conditions where the available current on short circuits
exceeds the limits fixed by the National Electrical Code.

Limits. — The capacity of a single generator panel is usually
limited to 1000 amperes, a single feeder circuit to 600 amperes,
and a complete switchboard composed of these panels to 2000
amperes in any section of the bus bars. Where the total capa-
city exceeds 2000 amperes the panels should be arranged with the
feeders and generators interleaved in such a way that no part
of the bus will have to carry more than 2000 amperes.

Voltage Readings. — With the apparatus supplied on the gen-
erator panels and with the bus instrument equipments, provision
is made for the indication of voltage on one phase of the bus and
on any phase of the machine. Provision can be made for indica-
tion of voltage on any phase of the bus and on one phase of the
machine. Synchronizing is done between bus and machine by
means of a synchronoscope.

If a sectionalized bus is used, a voltmeter switch is needed to
transfer the bus voltmeter to either section of the bus. The bus
instrument equipments include lamps for mounting on the
panels for continuous ground indication.

Generator panels include drilling for remote-control rheostat
mechanism, but the mechanism is not included as part of the
switchboard. No automatic overload protection for the gen-
erator armature or field circuits is supplied. Enclosed fuses
provide automatic overload protection for the feeder circuits.

Switches. — Round stud knife switches without quick break
attachments are furnished with standard panels. When cir-
cuits must be frequently opened under load, quick break switches
are recommended for 100 amperes and above.

Blank Panels. — It is desirable to install blank panels in cases
where the future equipment cannot be placed at either end of
the board. Such provision at the time of the original installa-
tion makes it unnecessary to move existing panels and connecting
conductors at the time of making additions.

Panels with single-throw switches, for operating with a single
bus system only, are usual. Panels with double-throw switches
for operating with a double-bus system can be supplied. Ordi-
narily, for plants of moderate capacity the sectionalizing of the
lighting load and the power load may be obtained by grouping
all the lighting circuits on one section of the bus and the power

HAND OPERATED A.C. SWITCHBOARDS 363

circuits on the other section, the two sections being connected
together, when desired, by a switch. This permits carrying all
the load with one machine during light-load periods.

A.C. SWITCHBOARDS WITH OIL CIRCUIT BREAKERS

For higher voltages and in many cases for moderate voltages
it is advisable to utilize oil circuit breakers and these may be
mounted directly on the rear of the switchboard or made distant
control operated mechanically or electrically depending on
various circumstances. The general appearance of the A.C.
panel switchboards is largely influenced by the type of instru-
ments used and by the cover plate or control device employed
with the oil circuit breakers.

These switchboards are designed to control the alternating-
current electrical equipment of central and distributing stations
and industrial plants.

Direct-control. — These boards are designed for plants not
exceeding 3000-kilovolt-amperes capacity, requiring panels not
exceeding 800 amperes capacity, where the voltage is not over
2400 and where it is not so advantageous to locate the oil switch-
ing devices apart from the panels.

Hand Remote Control. — These switchboards are applicable
where the simplicity of connections or accessibility desired cannot
be obtained with panel mounted apparatus, where station capa-
city of voltage is so high as to make it desirable to mount switch-
ing equipment apart from panels, and where station arrangement
permits the use of manually operated remote control oil circuit
breakers.

Electrical Remote Control. — These switchboards are applicable
where the equipment must be remote controlled but where
manually operated switchboard apparatus is not suitable.

Accessibility. — To make the rear of the switchboard more
accessible, all the current transformers are usually furnished for
mounting apart from the panels, and arrangements should be
made for mounting these transformers in the main leads in the
most suitable location. Voltage transformers will usually be
mounted on the rear of panels, as this location is advisable in
order to get the advantage of short primary leads and ready
access to primary fuses. This applies chiefly to direct-control
switchboards.

364 SWITCHING EQUIPMENT FOR POWER CONTROL

Panel Frame Mounting. — Additional advantages in construc-
tion can often be obtained by the use of breakers mounted on
panel framework. Usually oil circuit breakers, both non-auto-
matic and automatic, can be supplied for mounting on horizontal
pipes attached to the panel framework back of the operating
handle, as shown in Fig. 220. In general, the panel frame mount-
ing gives a better construction, in that connections from circuit-
breakers to bus bars are more nearly

C c 3Li=s=s==s=ss=s=si | direct and more space is available for
taking away connecting cables to
panels and for mounting switchboard
details. Some of the other advantages
are the following: less likelihood of
oil getting on panels; the weight of
breakers is carried on frame instead
of on panel; the rear of the panels is
more accessible; several types and
capacities of breakers have inter-
changeable mountings; with narrow
panels the position of the breaker
handle is not restricted to the center
of the panel so that knife switches
and handles for remote control breakers can often be added
where this would be impossible with direct panel mounting
unless wider panels are used.

Voltage Readings. — With apparatus supplied on the generator
panels and with the usual bus instrument equipments, provision
is made for reading the voltage on one phase of the bus and on any
phase of the machine for 240, 480, and 600-volt systems, when
voltmeters are wound for primary voltage; and for reading the
voltage on any phase of the bus and on one phase of the machine
on systems of higher voltage, or in cases where voltmeters are
wound for secondary voltage on systems of 600 volts and under.
Synchronizing is done between bus and machine by means of a
synchronoscope.

If the voltage indication on all three phases on the machine
side of the generator circuit breaker is desired for panels having
secondary voltage instruments, it is necessary to supply with
each generator panel a 3-phase voltmeter switch, and an addi-
tional voltage transformer.
Meter Equipment. — Direct-control switchboard equipments

FIG. . 220. — Switchboard with
panel frame mounted breakers.

HAND OPERATED A.C. SWITCHBOARDS

365

include power factor meters, wattmeters, and watt-hour meters
with windings for bus voltage for 240 and 480 volts, and volt-
meters and frequency meters with coils for bus voltages for 240,
480 and 600 volts. For bus voltages above these values, voltage
transformers are required. Synchronoscopes require voltage
transformers for all voltages above 115 (nominal).

FIG. 221. — Typical low voltage Westinghouse switchboard.

The question of the arrangement of circuit breakers and bus
bars will be considered later and a few typical examples of General
Electric and Westinghouse panel boards will be given to illus-
trate the principal features of design.

Westinghouse Switchboards. — Fig. 221 shows a typical low
voltage A.C. Westinghouse switchboard for the control of two
exciters, one exciter motor, two generators and two feeders.
On swinging brackets are placed two voltmeters, one connected
to the bus and the other plugging on any generator, and a
synchronoscope with two synchronizing lamps.

366 SWITCHING EQUIPMENT FOR POWER CONTROL

The double exciter panel contains two 2-pole exciter main
switches, one single-pole equalizer switch, two exciter ammeters
with one voltmeter and voltmeter switches for connecting it to
either exciter. The next panel for the exciter motor contains
the handle for the auto starter and an ammeter.

Each generator panel contains an A.C. ammeter with three-
way switch to connect it to any phase, a polyphase indicating
wattmeter, a field ammeter, voltmeter and synchronizing
switches, field rheostat and field discharge switch with resistor
and main 3-pole knife switch.

FIG. 222. — Panel switchboard, hand operated breakers — General Electric Co.

G. E. Panel Board. — Figure 222 shows a typical General Elec-
tric switchboard supplied to the Catton, Neill & Co., Ltd., of
Honolulu, H. I. This board controls two exciters, one 480 volt
3 phase 3 wire A.C. generator, one 480 volt 3 phase 3 wire incom-
ing line, six 480 volt 3 phase 3 wire power feeders and various
lighting feeders. The synchronoscope, exciter voltmeter, etc.,
are mounted on swinging panel adjoining exciter panel. The
three phase generator panel is provided with horizontal edgewise
A.C. ammeter, voltmeter, indicating wattmeter and field am-
meter, field rheostat, field switch with discharge clips, voltmeter
and synchronizing receptacles, non-automatic generator main
switch, watthour meter and testing receptacles. The next panel
is the incoming line panel and is provided with indicating meters,
voltmeter and synchronizing receptacles, ammeter plug recep-
tacles, plunger type overload relays, automatic oil circuit breaker,

HAND OPERATED A.C. SWITCHBOARDS

367

watthour meter and calibrating receptacles. The next four
panels are power feeder panels controlling a total of six circuits
and each circuit is provided with the following:

Ammeter

Ammeter plug receptacles

Ammeter plunger type overload relays and automatic oil
circuit breaker.

The panels at extreme right hand end of switchboard control
various lighting circuits, each circuit provided with a 3 pole
knife switch properly fused.

FIG. 223. — Electrically operated switchboard round meters.

Electric Operated Switchboard.— Fig. 223 shows a typical
panel switchboard using 7-inch diameter black dial round pattern
instruments with distant electrical control oil circuit breakers.
The swinging bracket contains the bus voltmeter, the machine
voltmeter, the exciter voltmeter and the synchronoscope with
two synchronizing lamps. The first panel on the left contains
the voltage regulator for three exciters not operating in parallel
and contains the various relays, rheostats, switches, etc., needed
for the regulating equipment. Each of the next three panels

368 SWITCHING EQUIPMENT FOR POWER CONTROL

controls a generator with its direct connected exciter. Each
panel is provided with an ammeter with three way ammeter
switch, a polyphase indicating wattmeter, a field ammeter, an
exciter rheostat, field switch with discharge resistor, a volt-
meter and synchronizing receptacle, a control switch for the
motor operated generator rheostat, a control switch for the gover-
nor motor, a control switch with indicating lamps for use with
the electrically operated breaker in the generator circuit, two
single-phase overload relays and a watthour meter. The re-
maining panels are feeder panels, one of them containing a
graphic wattmeter.

FIG. 224. — G.E. truck type switchboard front view.

Truck Type. — One of the latest developments in the way of
A.C. panel switchboards is the truck type of design shown in
Fig. 224 in front view with one of the trucks withdrawn, and in
side view Fig. 225. This type of switchboard is made up of re-
movable truck type panels and can be supplied in separate units
or built up to form a complete switchboard with its accessories.
Connections are automatically broken as soon as the truck is re-
moved from the compartment, positively insuring that workmen
have no live parts to handle. One great advantage is obtained in
that continuity of service is assured. Should a breakdown occur,
a spare unit can immediately be placed in service without taking

HAND OPERATED A.C. SWITCHBOARDS

369

the power off the main bus thereby interrupting the service on
other sections of switchboard. This gives great flexibility to the
station.

Limits. — These panels can be supplied for voltages up to 7500
and current-carrying capacity up to 800 amperes; also in various
combinations of oil circuit breaker, instrument transformers and
meters.

FIG. 225. — G.E. truck type switchboard, side view.

Construction. — The general construction of the complete panel
is shown. All H. T. bus bars and cable connections are carried on
substantial porcelain insulators mounted in the frame supports
which are built up to form a complete cell structure. The frame-
work is so designed that a new panel can be added at any time,
the complete structure being finished off by cover plates bolted
to the ends of the bus bar chamber, except in cases where cables
are to be connected direct to the bus bars. In such cases a
cable box can be fitted to the opening at the end of the bus bar
chamber. Horizontal partitions are fitted above and below the

370 SWITCHING EQUIPMENT FOR POWER CONTROL

bus bars so that the latter are enclosed in a separate and con-
tinuous chamber. Where space is available behind the panel,
access can be obtained to these chambers by removing the back
and top covers. Where space is limited, however, the complete
cell structure can be built against the wall, access to the back
being obtained through the hand holes provided.

Covers. — Protecting covers for cables and bus bar terminals
can be supplied, so that when it is necessary for work to be
done in a cell, while the terminals are alive, these covers can be
padlocked in position and the work can be done with perfect
safety. Portable cell doors can also be supplied for closing any
cell from which the truck has been removed.

Mounting. — The whole of the apparatus for each circuit
equipment, including the oil circuit breaker, instruments and
transformers is mounted on a movable truck. This truck can bo
withdrawn in the space allocated to the attendant, and then
wheeled away for inspection. The open construction of the
truck framework renders inspection of all the apparatus a very
easy matter.

Contact Jaws. — The truck carries contact jaws mounted on
porcelain insulators which engage with contact blades mounted
in the fixed portion of the structure. These contact blades are
sunk into the porcelain insulators so as to obviate danger of acci-
dental shock or short circuits when the truck is removed. The
same insulators also support the bus bars in the bus bar chamber
and the cable terminals in the cable box chamber.

Interlocks. — Safety interlocks are fitted to all trucks, so
that it is impossible for any truck to be withdrawn from the
cell while the oil circuit breaker is closed; similarly the truck
cannot be pushed into the cell unless the oil circuit breaker is
open.

All parts are held together by means of bolt and lock nuts, so
that any part can be readily removed and replaced in a sound
mechanical manner.

The small wiring between the current transformers, trip coils,
and instruments is permanently connected up and mounted on
porcelain insulators attached to the frame of the truck.

The whole equipment is arranged so that ample clearances
are allowed between the conductors, and from conductors to
ground.

HAND OPERATED A.C. SWITCHBOARDS

371

ELECTRICALLY OPERATED EQUIPMENTS
Arrangements. — Various standard arrangements for electric-
ally controlled equipments are shown in Fig. 226. 'A' illus-
trates a typical vertical panel board with the instruments, con-
trol switches, relays, and similar devices mounted on the face
of the panel. 'B' shows an arrangement of a control desk with
the control switches placed on the desk and the instruments
mounted on a wall in front of the operator. 'C' shows an
arrangement of control desk where there are only a comparatively
few meters, these being set flush in the face of the desk. ' D '
shows a modification of the desk arrangement with the meters
on a small slab or bracket extending up from the horizontal slab

FIG. 226. — Arrangement of electrically operated boards.

of the desk. ' E ' shows the control desk arrangement with verti-
cal panels forming the back of the desk, the vertical panels
containing the indicating meters. 'F' is a further modifica-
tion of the control desk arrangement with vertical panels con-
taining the indicating meters and a complete switchboard at
the rear to contain the recording meters, relays, and similar
devices. With this arrangement a self-supporting control desk
is provided. ' G ' shows the so-called gallery type of desk with
the meters located on a framework supported above the hori-
zontal slab of the desk at such a height that the operators
standing at the control desk can look above the edge of the desk
and below the meter panels to observe from the switchboard
gallery the machine which he is controlling. ' H ' is a modifica-
ation of the gallery type of control desk. '!' is a modified
arrangement of control desk using a separate instrument frame
supported on ornamental pillars, these pillars as a rule, being
arranged to form the supports of a gallery railing. 'J' shows

372 SWITCHING EQUIPMENT FOR POWER CONTROL

the combination of utilizing a gallery type control desk for the
generators and vertical panel switchboard for the feeders. ' K '
shows a combination control desk and panel board, the gen-
erator breakers being controlled from the desk, the generator
instruments being on the vertical panels and all of the feeders
being controlled from the vertical panels. The recording meters,
graphic meters, and relays are placed on an auxiliary board
back to back with the feeder board. *L' shows an arrangement
of control pedestals and instrument posts.

Pedestals. — In some of the earlier large capacity power plants
equipments of control pedestals and instrument posts were
utilized in place of vertical panels in conditions where present
day practice would probably select the control desk as being
the most suitable arrangement. Some of these earlier equip-
ments of pedestals and posts have been superseded by more
recent control desks but others are still in operation.

Where the number of generators was comparatively small in
comparison with the number of feeder circuits, it was considered
frequently of advantage to use control pedestals and instrument
posts for the generator circuits and to take care of the feeder
circuits by means of a panel switchboard. The instrument posts
and control pedestals were self-contained, and additional posts
and pedestals could readily be added with additional machines,
without disturbing the symmetry of the arrangement.

Union E. L. & P. Co. — The original installation of pedestals
and posts in the switching galleries of the Union Electric Light
& Power Company of St. Louis is shown in Fig. 227, this equip-
ment having been furnished for the control of eleven 6600- volt, 25-
cycle, 3-phase generators of various capacities and a large
number of feeders. The generator controlling devices were
located on the pedestals, while the generator instruments were
placed on posts, the posts acting as supports for the gallery
railing. A station post containing voltmeters, synchronoscopes,
etc., was so located that the instruments could be observed from
any portion of the gallery. With the arrangement shown the
operator on the switchboard gallery at the end of the station
faced the generator room, while standing at the control pedestals
and watching the generator instruments. The feeders were
controlled from the panel board back of the operator, while the
masonry structure for the bus bars and connections was back of
the feeder board and located on the control gallery, as well as

HAND OPERATED A.C. SWITCHBOARDS 373

several lower galleries. Since the time of the original installation,
the switchboard gallery was enclosed in glass, and the generator
instruments were taken off the instrument posts, and placed on
swinging panels attached to the framework of the glass enclosure.
A later arrangement, due to remodeling of the plant makes use
of a control desk equipment.

FIG. 227. — Pedestals and posts of Union Electric L. & P. Co. of St. Louis.

Generator Pedestals. — Each generator pedestal was provided
with a controller for an electrically operated field discharge
switch, a drum controller (or a motor operated field rheostat, a
drum controller for the engine governor, three oil circuit-breaker
controllers with electro-mechanical tell tale devices and a
4-point voltmeter receptacle. At the top of the pedestal were
placed synchronizing and signal lamps, while the synchronizing
receptacles and plugs were located on each side of the lower
circuit-breaker controllers. Each pedestal had a height of 4
feet 8^4 inches and occupied a floor space 14 inches square.

Generator Posts. — Each generator instrument post was equip-
ped with a direct-current field ammeter, a 3-phase power factor
indicator and three A.C. ammeters. These posts were provided
with railing sockets and formed the supporting posts for the
railing at the edge of the switchboard gallery. These instru-
ment posts were made to contain various combinations of instru-
ments, and had a standard height of 5 feet 7K inches to the bot-

374 SWITCHING EQUIPMENT FOR POWER CONTROL

torn of the lowest meter, the total height to the top of grill work
above the upper meter being about 8 feet 10 inches.

The Ontario Power Co. Control Room, at Niagara Falls, Ont.,
is shown in Fig. 228. At the time this photograph was taken the
plant contained seven 8770-K.V.A. 12,000-volt, 3-phase gen-
erators, with banks of three 3000-K.V.A. transformers stepping
up to 60,000 volts. The 60,000-volt feeder circuits running to
Rochester, Syracuse, etc., were controlled from the panel board,
while the two smaller pedestals placed near the telephone desk
were used for the control of the exciter circuits. Various changes

FIG. 228. — Control pedestals & posts of Ontario Power Co.

have been made due to modifications in the excitation system and
plant at present comprises sixteen units and most of the energy is
now delivered to the Hydro Electric Power Commission of
Ontario.

Control Pedestals. — Each of the seven control pedestals was
equipped with push-button control for the generator field rheo-
stats and with a white signal lamp, that lit up when the field
circuit was closed. The miniature bus placed on the face of the
control pedestal shows two electrically operated oil circuit
breakers in the main generator circuit, one placed in the power
house at the foot of the cliff and the other being placed in the dis-
tributing station. The circuits from the generator after passing
through these two breakers connected by the breaker controlled
from the lower left-hand controller to one 12,000-volt bus in the
distributing station, or passed through the breaker controlled
by the middle controller to a common connection, where it
branched and passed either through another breaker to a second

HAND OPERATED A.C. SWITCHBOARDS 375

12,000-volt bus, or through a breaker on the low tension side of
the step up transformers. The controller in the extreme upper
right-hand corner took care of the breaker in the high tension side
of the step up transformers. The two remaining controllers
with circular handles were used, one for the control of the field
rheostat and the other for the control of the speed governor motor.
Suitable synchronizing lamps and receptacles were also placed
on these pedestals. This type of pedestal is 5 feet 0 inches high
and occupies a floor space approximately 24 inches by 14 inches.

Instrument Post. — Each post was provided with a single phase
synchronoscope, a frequency meter, a 3-phase power factor
indicator and transformer and generator ammeters and similar
instruments. The base of the instrument post contained a
number of calibrating jacks to permit the calibrating of the
instruments without removing them from the posts. The total
height of this post was 9 feet 0 inches and the width occupied by the
meters was 2 feet 7% inches.

Control Desk. — The control desk has many advantages where
a very compact arrangement is desired to control the generators
and feeders from the same switchboard, particularly where a
group system of circuits is used and it is desirable to have a
miniature bus bar to show the general scheme of connections and
the arrangement of circuits in use. The desk has mounted
on it the various controllers for the circuit breakers, field switches,
field rheostats, etc. It is customary to mount the instruments
in such a position relative to the sections of the desk, as to indicate
clearly to the station operator the instruments belonging to any
particular circuit.

With control desks the instruments can be mounted either
on independent switchboards or panels forming the back of the
control desk, or on an instrument frame back of and usually
higher than the top of the control desk, or on instrument posts.
In some cases the instrument can be set directly in the face of the
desk.

Fig. 229 shows the front elevation drawing of the control
desk supplied to the Williamsburg Generating Station of the
Brooklyn Rapid Transit Company for the control of a number
of 7500-K.V.A. and 10,000-K.V.A. turbogenerators, the desk
as shown being intended for the control of nine machines.

Generator Equipment. — Each generator is provided with two
electrically operated oil breakers in series with suitable discon-

376 SWITCHING EQUIPMENT FOR POWER CONTROL

necting switches so that each generator can connect to its own
feeder group bus or to the main bus. This main bus is sec-
tioned by means of electrically operated oil breakers between
generators 3 and 4, generators 5 and 6 and generators 7 and 8.
Group breakers are also provided for connecting the feeder group
busses to the main bus. Each feeder group bus supplied from

FIG. 229. — Front elevation desk, Brooklyn rapid transit.

three to six feeder breakers. The generator instruments are
placed on a framework above the desk, so arranged that the
station operator can readily watch the machines which he is
controlling. Each generator section is provided with a field
ammeter, an A.C. ammeter, a polyphase indicating wattmeter
and a power factor meter, while a voltmeter was set in the top of
the desk for one generator section in each group. A synchrono-
scope, frequency indicator and voltmeter were placed on a pivoted
slab attached to the center-post of the instrument frame back of
the desk.

HAND OPERATED A.C. SWITCHBOARDS

377

A sectional view is shown in Fig. 230 of this same control desk
which indicates the relative location of the desk and instrument
board, as well as the location of the apparatus on the face of the
control desk with the relays and similar devices on the back of the
desk.

FIG. 230. — Side elevation desk, Brooklyn rapid transit.

Feeder Board. — The feeders in this installation are controlled
from a vertical steel switchboard arranged in the form of an arc of
a circle back of the control desk, so that the station operator
turning around from the generator desk can readily observe any
of the feeder circuits. This feeder switchboard is made of two
concentric boards placed back to back, the board on the concave
side next to the generator desk containing the feeder indicating
instruments of the vertical edgewise type, and the controllers
and indicating lamps used with the electrically operated breakers
of the feeder circuits, while the switchboard on the convex
side contains the polyphase watt-hour meters, the overload
relays and the calibrating switches supplied for the various
feeder circuits.

378 SWITCHING EQUIPMENT FOR POWER CONTROL

Desk with Horizontal Edgewise Meters. — Fig. 231 shows a
control desk with horizontal edgewise meters placed on slate
slabs above the desk, while the various control switches with their
indicating lamps are mounted on the slate apron of the desk and
the time limit relays are located on the front panels of the desk.
With the arrangement shown the station operator faces the
generator room when standing at the desk and looks over the
desk and under the frame to watch the machines.

FIG. 231. — Control desk. G

Electric Co.

Desk with Vertical Edgewise Meters. — A control desk with
vertical edgewise meters supplied to the Pratt Street Power House
of the United Railway & Electric Company of Baltimore is
shown in Fig. 232, controlling a number of 13200-volt, 25-cycle,
3-phase, generators and outgoing feeder circuits. This desk
was arranged to form an arc of a circle and was ultimately to be
about twice as large as the portion shown. A complete minia-
ture bus bar system located on the top of the desk shows the
connections made by the various breakers that were arranged
on a group and ring system. In this plant each generator was

HAND OPERATED A.C. SWITCHBOARDS 379

provided with a circuit breaker connecting the generator to its
own bus bar. This bus bar connected in turn through a main
breaker to the main bus or through either of the two group
breakers to two group busses, each group bus supplying the cur-
rent to four feeder circuits. By closing the various group
breakers, the group busses form one complete ring bus and the
main bus forms the second ring bus, so that a very flexible arrange-
ment was secured.

Calibrating jacks were installed on the front panels of the con-
trol desks to permit any of the switchboard instruments to be

FIG. 232. — Control desk with vertical edgewise meters.

calibrated in position. The vertical edgewise instruments were
mounted on steel plates forming the instrument frame, while the
relays were located on the rear of the desk.

Desk with Round Pattern Meters. — Fig. 233 shows a control
desk of the gallery type furnished by the Westinghouse Electric
& Manufacturing Company to the Inawashiro Hydro Electric
Company of Japan for the control of four exciters, six 7700-K.V. A.
generators, four banks of transformers, various feeder circuits.
The desk comprises a pipe framework having mounted on it
nine sections of marine finished slate containing the various
controllers, indicating lamps and similar devices while a separate
instrument frame is furnished supported by pillars from the
control desk and containing the various meters needed for the
installation.

All of the controllers and indicating lamps for the D.C. sys-
tem of exciters and field circuits are placed on the front of the

380 SWITCHING EQUIPMENT FOR POWER CONTROL

desk while the controllers and similar devices for the A.C. cir-
cuits are located on the horizontal top of the desk.

A complete miniature bus bar system is placed on the desk to
show the connections made by the various breakers, red indi-
cating lamps being connected into the miniature bus bar system

FIG. 233. — Control desk with round pattern meters for Inawashiro.

in such a manner that they light up when their particular breaker
is closed. The miniature high tension bus on the horizontal slab
of the desk is nickel plated and the corresponding low tension
bus is polished copper. The field and excitation bus is distin-
guished by its location on the front part of the desk.

CHAPTER XV
BUS BARS & WIRING— GENERAL INFORMATION

Having considered the apparatus and the panels that are used
for the switching equipment, the next important matter to be
taken up is that of the bus bars and wiring; after which the
arrangements of breaker and bus structures and the general
layout of the portion of the power plant devoted to the switching
apparatus will be discussed.

Bus Bars. — In order to provide facilities for utilizing the cur-
rent developed in an electrical generating station to the best
advantage, it is customary to have one or more sets of circuits
into which the various generators deliver their current and from
which the various feeders draw their current. These common
circuits are known as "omnibus bars" or "bus bars."

In the simplest station with only one generator and only one
feeder the generator connects directly to the feeder but in practic-
ally every other case, with more than one feeder or more than
one generator, bus bars are required.

D.C. Busses. — With shunt-wound D.C. machines it is nec-
essary to have a positive bus and a negative bus; while if two
shunt machines are run in series, on a 3-wire system, a neutral
bus is also needed. With compound wound generators an equal-
izer bus is required, and when two compound wound machines
are run in series on a 3-wire system or when a compound
wound 3-wire D.C. generator is used, five busses are needed —
positive, positive equalizer, neutral, negative equalizer and
negative. For 2-wire service the feeder circuits only connect
to the positive and negative bus bars while for 3-wire service
they also connect to the neutral, but the equalizer busses only
connect to the generators. For railway circuits with ground
return the feeders only connect to one bus, usually the positive,
the other main bus (the negative) being grounded and the equal-
zer bus merely running between machines.

A.C. Busses. — In single phase A.C. systems there are two
busses, in 2-phase systems usually four busses, and in 3-phase

381

382 SWITCHING EQUIPMENT FOR POWER CONTROL

usually three busses. The single-phase system may be 3 -wire,
the 2-phase may be 3-wire or 5-wire, while the 3-phase may be
4-wire with the corresponding number of bus bars.

Where there is only a single set of bus bars either in D.C.
or A.C. stations the connections are said to be arranged on
the "single throw" system; when the connections can be made
to either of two sets of bus bars the system is spoken of as "double
throw", while if the connections can be made to both sets of bus
bars instead of only to either set the system is spoken of as the
"selector system." Occasionally three or more sets of bus bars
are used.

If there is only one set of bus bars but switches are provided
for dividing it into one or more sections it is spoken of as a sec-
tioned bus. Where there are two sets of these sectioned bus
bars connected together at the ends, the system forms a ring bus.
In many high voltage plants having step up transformers each
generator normally connects to the low tension side of its own
transformer but switches are provided so that any transformer or
generator can connect to a bus, such a bus is spoken of as a relay
bus. Where a number of feeders connect to a bus which in turn
connects to the main bus through a switch or breaker such a bus
is spoken of as a group bus. These various arrangements are
shown on the diagrams in a previous chapter.

Systems. — The various systems — single bus, double bus, relay
bus, group bus, etc., all have their advantages and disadvantages.
The single bus is naturally the cheapest, simplest and least
flexible and trouble on the bus is apt to shut down the plant.
The other systems are more flexible, and also more expensive as
they require more apparatus. In every installation a compro-
mise must be effected between cost and flexibility, and each case
must be considered on its own merits. In small low voltage
plants bus bar trouble is almost unknown and a single-throw
system is usually employed. In high voltage large capacity
plants although bus bar trouble is rare, a more flexible system
than the single throw is often advisable.

Material. — Depending on the current and voltage, bus bars
may be made of wire, rod, tubing, cable or strap, either bare or
insulated. Solid wire is seldom used for more than 200 amperes,
rod for 1000 amperes, tubing 300-600, cable 1000, while strap is
used up to any capacity. Strap for bus bars possesses several
advantages over other shapes, the chief ones being the ease with

BUS BARS AND WIRING— GENERAL INFORMATION 383

which additional straps may be installed and the excellent radi-
ating surface secured.

Straps of different sections are in use, a typical one being
3 inches by 3^-inch. Where more than one strap is required,
a space is kept between adjacent bars making the so-called
laminated bus. The usual spacing left with 3 inches by ^-inch
bars is %-inch. The connections from switches, circuit breakers,
etc., to the bus are made of one or more similar straps suitably
interleaved and clamped together.

Current Capacity. — Due to the large surface exposed in com-
parison to the section of copper used, comparatively high cur-
rent density may be employed for a small number of straps with-
out exceeding a safe temperature rise. The exact amount of
current to be carried for a given rise depends somewhat on
local conditions, ventilation, etc., and whether the bus is being
used for direct-current, 25-cycle, or 60-cycle service, and the tem-
perature rise is not the same for different parts of the bar. A
typical test under average conditions, 60-cycle service, 25-degree
rise, indicated that one bar would carry 650 amperes, two bars
1150 amperes, three 1500, four 1800, five 2000, six 2160, showing
that due to "skin effect," lack of ventilation, etc., the permissible
current density falls off rather rapidly as the number of bars
increases. It is usually necessary to interleave the phases for
60-cycle service to carry 3000 amperes or more without an ex-
cessive amount of copper.

Bus Compartments. — In large capacity A.C. plants of 13,200
volts or less, with generators connected directly to the bus, the
amount of current that can be concentrated on a short circuit
is something enormous and every precaution has to be taken to
prevent trouble from spreading if it ever starts. For this reason
it has become customary to employ masonry compartments
and cellular construction for the oil circuit breakers and
bus bars.

As the main idea of the cellular scheme is to provide an insulat-
ing fireproof barrier between leads of opposite potential in heavy
capacity plants of 13,200 volts or less the material to be used for
the structures, barriers, etc., is of the utmost importance. The
vertical walls and septums of the circuit-breaker and bus bar
structures are usually built of brick or concrete while the horizontal
shelves between the bus bars are ordinarily made of concrete,
soapstone, slate or marble. In some instances the bus bar struc-

384 SWITCHING EQUIPMENT FOR POWER CONTROL

tures have been made of asbestos lumber, transite or similar
material.

Brick Work. — The brick used for structural work of this kind is
usually a good class of pressed brick, fire brick or enameled brick
put up with cement mortar and presenting a fine appearance. In
order to keep down the cost, it is sometimes arranged to use the
finer grades of brick for such portions of the structure as are
visible from the operating room or noticeable to the average
visitor while a cheaper grade is used for such other parts as are
normally not seen. The advantages of brick for this class of
work are that it has ample strength to support the weight and to
stand the jar of opening of a heavy breaker, and it is easy to
secure good bricklayers in almost any locality. Its disadvant-
ages are chiefly due to its relatively fixed dimensions, the difficulty
of reinforcing thin walls of any considerable height and the trou-
ble experienced in locating conduits for control leads, etc., as
well as the fact that it is practically impossible to make the hori-
zontal shelves of the same material as the vertical walls when brick
is used.

Concrete. — This possesses most of the advantages of brick
without the disadvantages of relatively fixed dimensions and
as it can be easily reinforced and can be made into horizontal
shelves for bus bar work it is rapidly becoming a favorite material
for such structures. When concrete is used it is a simple matter
to imbed the conduit for the control leads, the tie rods for the
breakers, the bolts for switch bases, transformers, etc. in the
structure. Concrete, however, is somewhat more apt to absorb
moisture than brickwork but when dry is a comparatively good
insulator and resists the destructive effects of an arc as well as
anything used for the purpose.

Shelves. — Horizontal shelves between bus bars have been
made of marble, slate, soapstone, sandstone, concrete or similar
material and historically they have been used about in the order
named which is also the order of their decreasing cost. Marble
is undoubtedly the best material as far as insulation and absorp-
tion qualities go, but its high cost and its crumbling when exposed
to a bad arc has caused the adoption of cheaper materials of
slightly poorer insulating qualities. Slate, the next material
tried, is a very uncertain insulator for high voltage work and it
has been generally superseded by soapstone, sandstone or con-
crete. Where space is at a premium, soapstone is used almost

BUS BARS AND WIRING— GENERAL INFORMATION 385

exclusively as it can be drilled, machined, etc., and smaller
clearance distances can be used than would be permissible with
sandstone or concrete. Where there is a chance to secure a
reasonable distance between bare metal parts and the shelves
or barriers, concrete, either plain or reinforced, can be used to
advantage.

Between disconnecting switches and in such places where the
barrier wall does not carry any additional weight, asbestos board,
wire glass, etc. has sometimes been used.

Enclosures. — Masonry structures for bus bar work are made
either semi-enclosed or entirely enclosed. In the former case
the wall of the structure which separates the horizontal bus bars
and the vertical connections is made practically continuous.
The back of the bus bar shelves are built into this wall while
pilasters properly spaced support them in the front. Except
for these pilasters the bus bar structure is open in the front
and the septums in the rear that separate the leads are usually
left open. This scheme leaves the bus bars and connections
readily accessible and well ventilated but makes it possible for a
careless visitor or attendant to come in contact with the bus or
connection.

A modification of this scheme uses a continuous wall instead of
pilasters as a support for the front of the shelves and the bus bars,
connections, etc., are almost completely enclosed except for open-
ings provided with doors at the supports, contacts, etc. With
this arrangement it is impossible for any one to touch any live
metal parts without removing a door, but the busses, connec-
tions, etc., are not so accessible or so well ventilated as with the
more open arrangement.

Leads. — Where the leads pass through the floor or the back
wall of a bus bar structure, either of two schemes may be adopted.
With the first, porcelain bushings are used to give the necessary
insulation while with the other scheme holes of generous dimen-
sions are made and the lead run through the middle of this hole.
In one case porcelain insulation is used and in the other air.
The former makes a tighter joint with less likelihood of smoke or
flame passing from one compartment to the next but is more ex-
pensive and more subject to insulation trouble than the latter.

Connections. — For bus bars and connections where the cur-
rents exceed 600 or 800 amperes it is usual to employ laminated
copper straps while for smaller currents cable, wire, rod, or tubing

386 SWITCHING EQUIPMENT FOR POWER CONTROL

is used. Cable, and to a certain extent wire, is used for con-
nections involving bends or long runs through conduit, while
for straight runs or simple bends rod or tubing can be used.
Tubing while more costly than rod or wire for the same section
is stiffer and can often be flattened out for making connections to
studs, bars, etc. without the necessity of additional terminals.

Laminated Bus. — One of the advantages of the laminated
copper strap is the large amount of radiating surface secured
with the minimum amount of material, and the readiness with
which it is possible to taper the bus bars so as to utilize the ma-
terial to the best advantage adjusting the capacity of the bus to
the total amount that will have to be carried at any one point.

Another great advantage is the facility with which additional
strap may be added if it is desired to increase the capacity of the
bus at any time. Another advantage is the ready means by which
connections can be made if laminated copper straps are used
which will interleave with the bus, and which connect the bus to
the studs of disconnecting switches, circuit breakers or similar
appliances.

Supports. — As supports for the low tension bus bar, insulators
of various kinds have been designed, these usually being made of
porcelain either in the shape of cylindrical or conical pillars, or
in the form of petticoat insulators depending on the voltage of
the circuit.

Low tension bus bars, when not too heavy, can be supported by
the wall bushing for the lead. For heavier work, or where bush-
ings are not used, the bus bars are supported on porcelain pillars,
petticoat insulators, and similar devices resting on the bus bar
shelf, or attached to the wall.

Bus Stresses. — In the larger generating stations, due to the
tremendous values of short-circuit current resulting from the
size and number of turbogenerators represented in present day
station practice, close attention must be given to the adequacy
of the bus bar supports. Various curves and formulae have been
deduced for the purpose of calculating the mechanical strain on
bus bar supports at the instant of short circuit. A typical for-
mula is the following:

F = .27 X K.V.A.2 divided by A X V2 X Z2 where
F = maximum force exerted in pounds per foot of bus.
K.V.A. = normal rating of the station including all synchronous
apparatus.

BUS BARS AND WIRING— GENERAL INFORMATION 387

388 SWITCHING EQUIPMENT FOR POWER CONTROL

A — distance between busses in inches.

Z = impedance in per cent, expressed in decimals to the

point of short circuit.
V = line voltage.

Fig. 234 and 235 are graphic representations of this for-
mula. In using this formula a typical example with 150,000
K.V.A. station capacity at 6600 volts, 8 per cent, reactance
gives a maximum force on the bus bars per foot of length, 735
Ibs. with 30-inch spacing between bars, 1470 Ibs. with 15-inch
spacings between bars. With four feet between bus supports
each bus support would have to stand a strain of 2940 Ibs. if
the busses are 30 inches on centers, 5880 Ibs. if the busses are
15 inches on centers. For heavy duty of this kind, multi-point
supports are frequently used.

For supports of high tension bus bars and connections it is
customary to employ high tension insulators of the pillar type,
pin type, or suspension type, depending on the voltage.

Extra High Tension. — Where the generators connect through
separate transformers giving voltages from 22,000 to 154,000 or
even higher, the question of enclosing the bus bars and wiring
for the high tension circuits becomes an entirely different proposi-
tion.

Some engineers were originally of the opinion that the cellu-
lar construction should be used for large capacity circuits of any
voltage, and bottom connected breakers have been designed that
work in well with the enclosed bus bar construction for high
voltage plants.

Open Construction. — The almost universal American opinion
at present is that the open system of wiring is preferable for any
voltage higher than that for which generators can be conven-
iently wound. It is based on the following reasons:

First. — The violence of an arc and the destructive effect of
short circuits depends on the amount of current available at that
point. While fireproof barriers and cellular construction are
required on large capacity plants of comparatively low voltage,
they are unnecessary for higher voltage plants of the same or
even larger capacity.

Second. — The distance from wire to ground has to be greatly
reduced over what could be obtained with open wiring in the
same space as the fireproof barriers offer a more or less perfect

BUS BARS AND WIRING— GENERAL INFORMATION 389

390 SWITCHING EQUIPMENT FOR POWER CONTROL

ground for high voltage circuits and the higher the voltage the
more perfect the ground.

Third. — A more expensive building and costly construction
are usually needed for enclosed bus bars and wiring than are
required for open wiring.

Fourth. — Inspection and repairs are more difficult for bus bars,
wiring, disconnecting switches and similar appliances that are
boxed in masonry compartments, and are only visible and ac-
cessible by the removal of doors, than if everything is in plain
sight. Inspection will be more frequent and thorough and incipi-
ent trouble will be noticed far sooner with open wiring than with
enclosed, as the station attendant in a few minutes walk can see
everything and will not have to remove many doors and visit
two or three floors to examine the condition of the apparatus.

In most cases the desirable features of the open system of
wiring for high voltage can best be secured by the use of outdoor
transformers and switch gear.

Tubing. — For extremely high voltages with the corresponding
small current, copper tubing for bus bars and connections has
many advantages over rods, wire or strap, these advantages
being principally increased stiffness for the same amount of
material, large and effective radiating surface and the facility of
making connections by flattening out the tubing at the point
desired and bolting the tubing together at such points. Tubing
of approximately 1 inch outside diameter is not apt to be troubled
by the brush discharge or corona effect that is sometimes noted
with small wires or strap having sharp edges when used on ex-
tremely high voltage circuits. In many cases standard iron
tubing is employed.

Supports. — For supports for such high tension bus bars and
connections it is customary to employ line insulators either of
the pillar type, pin type, or suspension type, depending on the
voltage.

Connections. — For the connections between generators, trans-
formers, feeder circuits and their switching gear, it is occasionally
possible to use bare copper conductors, although in most cases
particularly for the connections between the generators, the
low tension side of step up transformers and their switch gear,
insulated wire or cables are better adapted for the actual arrange-
ment of the station.

Cables. — On all circuits of more than 200 amperes the leads

BUS BARS AND WIRING— GENERAL INFORMATION 391

usually consist of cables, the number and size depending on the
current to be carried and other considerations. It is often practi-
cable to use the same size of cable, e.g., 500,000 C.M. for all the
main connections in one plant, using as many cables in multiple
as may be required, and in this manner utilizing the cable to
better advantage than if each circuit had different sizes of leads.
Proper terminals can always be supplied on the switchboard or
machine to suit any reasonable cable requirements. The sizes
of cable used should usually correspond with the carrying capaci-
ties as given by the National Board of Fire Underwriters unless
there are considerations of excessive line drop in a long feeder or
some other reason for departing from their regulations.

Underwriters. — As far as possible all wiring, etc., on switch-
boards strictly corresponds with the requirements of the National
Board of Fire Underwriters, but it has been found impracticable
to attempt to wire up the back of switchboards used on voltages
above 600 with fireproof wire owing to the poor insulating quali-
ties of the fireproof covering and the consequent necessity of
stripping back this braid for several inches from all terminals,
etc., on the back of the board.

CONTROL AND INSTRUMENT CABLE

Multiple Cable. — For the connections between series and shunt
transformers, their instruments and relays, and between the
controlling devices, and the circuit breakers, switches, etc., that
are controlled, it is customary in American practice to supply
multiple conductor cables, each conductor being provided with
distinctive braid to facilitate the more ready checking of the
wiring after it is installed. This multiple conductor cable is
usually made either with a fireproof braid or with a lead cover,
and is frequently run in iron pipe conduit.

As the instruments and control switches for electrically op-
erated switchboards are usually located some distance from the
meter transformers, circuit breakers, rheostats and other acces-
sories, it is necessary to use connecting leads of varying lengths.
For this purpose, multiple conductor cables are used.

Size of Cable Required. — The sizes of conductors generally
used, where lengths do not exceed 500 feet, are as follows:

For current transformer circuits, each lead should be equivalent
to 19,500 circular mils and for very short runs 10,000 circular

392 SWITCHING EQUIPMENT FOR POWER CONTROL

mils. For potential transformer circuits, each lead should be
equivalent to 10,000 or 6,000 circular mils.

For small solenoid operated circuit breakers, closing coil leads
should be equivalent to 19,500 circular mils; tripping coil and in-
dicator leads equivalent to 6000 circular mils; return circuit being
same size as closing-coil lead, either in same cable or separate.

For large oil circuit breakers on control circuits of 125 volts
or lower, it is sometimes considered advisable to use a heavier
closing lead. In every case it is advisable to carefully check the
drop in the closing circuit to insure proper operation of the
breaker, as in some cases very heavy leads will be required.
When a relay switch is used, the lead from the control switch is

RUBBER-INSULATED, BRAID-COVERED, WEATHERPROOF AND FLAMEPROOF
MULTIPLE-CONDUCTOR CABLES FOR AUXILIARY CIRCUITS

Number
of con-
ductors

Stranding of each
conductor, inch

Circular
mils

Diameter, inches

Approx.
wt., Ibs. per
1000 ft.

Bare
copper

Over outer
braid,
maximum

19 of 0.0179

6,000

0.0895

0.57

150

19 of 0.0226

10,000

0.113

0.62

195

19 of 0.032

19,500

0.160

0.78

325

19 of 0.0179

6,000

0.0895

0.61

190

19 of 0.0226

10,000

0.113

0.66

225

19 of 0.032

19,500

0.160

0.84

430

One 19 of 0.032

19,500

0.160

0.70

230

Two 19 of 0.0179

6,000

0.0895

One 37 of 0.0359

47,500

0.251

0.81

415

Two 19 of 0.0179

6,000

0.0895

19 of 0.0179

6,000

0.0895

0.66

210

19 of 0.0226

10,000

0.113

0.72

300

19 of 0.032

19,500

0.160

0.92

540

One 19 of 0.032

19,500

0.160

0.76

375

Three 19 of 0.0179

6,000

0.0895

Two 19 of 0.032

19,500

0.160

0.76

375

Two 19 of 0.0179

6,000

0.0895

19 of 0.0179

6,000

0.0895

0.75

260

19 of 0.0226

10,000

0.113

0.82

350

Two 19 of 0.032

19,500

0.160

0.86

450

Three 19 of 0.0179

6,000

0.0895

19 of 0.0179

6,000

0.0895

0.80

385

19 of 0.0226

10,000

0.113

0.88

500

19 of 0.032

19,500

0.160

1.12

760

19 of 0.0179

6,000

0.0895

0.80

420

19 of 0.0226

10,000

0.113

0.88

540

BUS BARS AND WIRING— GENERAL INFORMATION 393

only large enough for the operating current in the relay switch,
for which purpose 6,000 circular mil cable is usually adequate.

For engine governor control or electrically operated rheostat
control, each lead should be equivalent to 10,000 or 6,000 circu-
lar mils; three, four or six leads being used, as required. The
cables listed below are particularly adapted to the diverse require-
ments of switchboard service.

Insulation. — Each individual conductor is insulated for 600-
volt service and is covered with braid with an identifying color.
The insulated conductors are assembled and covered with a
layer of tape and an outer braided covering or lead sheath.
The outer covering of the cable selected depends upon the nature
of the installation.

RUBBER-INSULATED, LEAD-COVERED, SINGLE AND MULTIPLE-CONDUCTOR
CABLES FOR AUXILIARY CIRCUITS

Number
of con-
ductors

Stranding of each
conductor, inch

Circular
mils

Diameter, inches

Approx.
wt., Ibs. per
1000 ft.

Bare
copper

Over outer
Braid
maximum

19 of 0.0226

10,000

0.113

0.37

390

19 of 0.032

19,500

0.160

0.45

530

37 of 0.0285

30,000

0.200

0.49

600

37 of 0 . 0359

47,500

0.251

0.55

720

19 of 0.0179

6,000

0.0895

0.65

600

19 of 0.0226

10,000

0.113

0.69

735

19 of 0.032

19,500

0.160

0.88

930

19 of 0.0179

6,000

0.0895

0.68

715

19 of 0.0226

10,000

0.113

0.73

805

19 of 0.032

19,500

0.160

0.94

1,180

19 of 0.0179

6,000

0.0895

0.73

800

19 of 0.0226

10,000

0.113

0.79

915

19 of 0.032

19,500

0.160

1.02

1,400

One 19 of 0.032

19,500

0.160

0.86

1,025

Three 19 of 0.0179

6,000

0.0895

Two 19 of 0.032

19,500

0.160

0.94

1,200

Two 19 of 0.0179

6,000

0.0895

19 of 0.0179

6,000

0.0895

0.82

1,200

19 of 0.0226

10,000

0.113

0.92

1,300

Two 19 of 0.032

19,500

0.160

0.90

1,400

Three 19 of 0.0179

6,000

0.0895

0.90

19 of 0.0179

6,000

0.0895

0.90

1,040

19 of 0.0226

10,000

0.113

1.10

1,200

19 of 0.032

19,500

0.160

1.25

1,700

19 of 0.0179

6,000

0.0895

0.90

1,075

19 of 0.0226

10,000

0.113

1.10

1,200

394 SWITCHING EQUIPMENT FOR POWER CONTROL

Colors of Leads. — The colors used by one manufacturer in
identifying the individual conductors are as follows: First,
black; second, white; third, red; fourth, green; fifth, yellow;
sixth, blue; seventh, yellow and green. For example, a four
conductor cable requires the use of the first four colors, black,
white, red and green.

When conductors of different sizes are used in a multiple con-
ductor cable, the sequence of colors given above is followed in the
order of the capacities, the largest conductors having a black
braid, the next largest a white braid, etc.

BUS SUPPORTS

Early Types. — In the earlier station designs the use of petti-
coat insulators mounted on pins for supporting high tension bus
bars and wiring was practically imperative, owing to the lack of
supports specially designed to meet the conditions. This prac-
tice was quite general and in some instances is still standard,
especially when extensions to old work are necessary. The use
of petticoat or line insulators had the advantage of employing
a standard part usually available or easily secured.

Progress. — There were, however, many objections to their
use, especially when compactness, flexibility and neat appear-
ance of bus bar work were important. The petticoat type of
insulator support is not well adapted for horizontal mounting,
and for installations where a back connected type is necessary
the petticoat form cannot be used to advantage. It is not easily
inspected or cleaned and in bus bar compartments the danger of
dust or dirt accumulation on the inner petticoat surface is appa-
rent. Owing to manufacturing difficulties, it is practically im-
possible to secure uniform dimensions of petticoat insulator
grooves, heights, etc., and as a result the general "line up"
of the conductor or bus is apt to be irregular. The large space
required is also frequently objectionable, especially when bus
bar or wiring compartments are used.

Pillars. — As station design progressed the bus bar or high ten-
sion wiring supports began to receive closer attention, first by
European and then by American engineers. The earlier Euro-
pean designs comprised a corrugated pillar having recesses at
both ends into which were rigidly cemented the desired fitting
to clamp a bus bar, mount on pipe frame work or flat support.

BUS BARS AND WIRING— GENERAL INFORMATION 395

Cementing. — The practical objection to this early foreign
standard was that the rigidly cemented fittings and insulators
resulted in an inflexible unit, difficult to install. In case of
changes in the number or size of busses, necessity of substituting
pipe work for flat base pins, etc., the limitations became very ap-
parent, as it was necessary to remove the entire unit, substituting
a second complete unit in its place. In short, the construction
employed in the early European designs was electrically good but
mechanically inconvenient, expensive and cumbersome. It was
a rigid, inflexible design not well adapted to American practice.

Another serious objection to the original type was that it was
impossible for manufacturers or users to carry a complete stock,
as the fittings of each particular size were rigidly cemented in
place and parts could not be interchanged. Factory shipments
were, therefore, slow and the user always had an equipment devoid
of interchangeable features.

Post Type. — The next step in design and manufacture of bus
bar supports was the "post type," consisting of a corrugated
post provided with removable top and bottom clamp fittings.
This improved design eliminated the interchangeability limita-
tions of the older pillar type, having rigidily cemented fittings,
so the parts could be adjusted or replaced as desired. The dis-
advantage of the "post type" support was that the method
adopted of attaching the top and bottom clamps on the outside
of the insulator materially cut down the leakage surface. As the
clamps extended over at least one corrugation, this design also
necessitated greater dimensions in order to maintain the same
factor of safety secured with the older form of cemented "pillar
type supports."

Clamps. — The clamps at top and bottom were also consider-
ably wider than employed with the older "pillar supports,"
necessitating wider spacings between insulators, greater clear-
ances for height, use of larger bus bar compartments and as a
final result a larger substation or station building.

These clamped supports are made by various builders with
different features. Those of the Westinghouse Company have
been selected as illustrating the general type.

Westinghouse Supports.— Type P bus supports of the West-
inghouse Electric & Manufacturing Company, with corru-
gated insulators consist essentially of an insulator with suitable
bus and mounting fixtures clamped on.

396 SWITCHING EQUIPMENT FOR POWER CONTROL

The insulators are made of porcelain by wet process and have a
brown mahogany glaze. The insulators are corrugated to insure
ample creepage surface under service conditions. The fittings
are made of malleable iron or cast brass and have a high-grade
dull black, baked finish. Interchangeability of fittings on porce-
lains of different voltage but of same diameter of head or base is
provided.

Stresses. — Mechanical stresses due to short circuits on the
bus bars must be considered in selecting the type and size of

FIG. 236. — Bus bar supports with braces.

support. These short-circuit stresses may depend on the
maximum ampere load, under short-circuit conditions, the dist-
ance between center line of bus bars and the relative location of
the bus bars.

To meet these varied requirements, several sizes of insulators
are made for the lower voltages, from which proper selection
may be made.

Heavy Supports. — Insulator supports for extra heavy busses
can be supplied, when desired, with insulator braces between the
bus bars, as shown in Fig. 236. The complete support and brace
are made up of standard parts. This arrangement is equally
adaptable for frame or cell mounting.

BUS BARS AND WIRING— GENERAL INFORMATION 397

Tests. — Voltage tests with all fittings on are given in table
below. These tests are ample for ordinary applications and are
well within the requirements of the recommendations of the
American Institute of Electrical Engineers. The large creepage
surface provided by the corrugations insures the ability of the
insulator to stand the same test under service conditions.

Maximum service voltage
7,500
15,000
25,000
35,000
44,000

One Minute
dry test volts

20,000

40,000

65,000

90,000
115,000

For exceptional installations where an insulator of a high volt-
age test may be desired, next higher maximum service class may
be used.

Fig. 237 shows an extra heavy duty bus arrangement, busses
vertically mounted in same horizontal plane with barriers.

FIG. 237. — Heavy duty bus support.

This arrangement employs standard supports requiring the
same number as is ordinarily used for single supports, but so
disposed that one half of the porcelains are in compression from
short-circuit stresses.

Compression. — The rating of the supports can be increased
to meet the demands of extra heavy duty, by so locating the

398 SWITCHING EQUIPMENT FOR POWER CONTROL

supports, that some of them will always be in compression under
short-circuit stresses.

A series of typical insulators with the various clamping devices
and switchboard details is shown in Fig. 238, while the applica-

FIG. 238. — Bus fittings & details.

tion of these devices and various standardized details as furnished
by the Westinghouse Company are shown in Fig. 239.

Delta-Star. — Other makers of fittings have adopted different
methods of attaching the metal parts to the porcelain insulators
and claim certain advantages for their designs. The Delta-

BUS BARS AND WIRING— GENERAL INFORMATION 399

Star Company have a line of "Unit Type Bus Bar Supports"
that they have developed and which they consider superior to the
clamped type for different reasons, given below.

Objections to Post Type.— Owing to their greater weight and
size, larger and heavier and more expensive supporting struc-
tures were necessary than with the pillar form. For moderate
potentials, 22,000 volts and less, the "post type" insulators
were abnormally large and heavy, did not permit of a neat
construction and were altogether out of proportion for the work

FIG. 239. — Westinghouse switchboard details.

to be accomplished. While the "post type" insulator was an
improvement from a manufacturing standpoint, it did not work
out so advantageously for the user, especially when making
extensions. Owing to the increased size and weight (necessitat-
ing greater clearances, etc.) it was frequently an impossibility
to install the "post type" in existing substations or wiring sys-
tems where a given place had been provided for future extensions.
Unit Type. — The problem presented by modern conditions
was then given close attention and after consulting experienced
power house engineers the final standard adopted was the " Unit
Construction" bus bar supports. These supports have all the
advantages of previous types with none of the disadvantages

400 SWITCHING EQUIPMENT FOR POWER CONTROL

and permit of a flexibility in manufacture, assembly and installa-
tion impossible to obtain in the older forms.

The "Unit Type" wet process corrugated porcelain pillars
are recessed at each end and provided with a sanded surface
socket in which is cemented a malleable iron thimble, threaded
to receive the proper fittings for the service to be met. The
advantages of this construction will be quickly appreciated by
engineers, as a flat base mounting can quickly be converted to a
pipe frame mounting, etc.

if]

FIG. 240. — Unit construction, bus bar supports.

Changes. — If future requirements make it desirable to change
bus bar sizes it is simply necessary to remove the original fitting
and install a new one of different type or size.

The wet process insulators are finished in dark brown glaze,
the metal parts having black enamel finish. This combination
of colors insures a pleasing, permanent finish corresponding to
other high-grade switchboard and bus structure equipment.

The "Unit Construction" has an additional advantage in that
bus bar supports can easily and quickly be reconstructed for
higher "potentials by the user. A good example of this desirable
feature is shown in Fig. 240. The support to be increased in
voltage rating is shown at 'A,' the insulator unit with bus bar
clamp removed at 'B,' the additional unit is in position at
'C' and the complete assembly is shown at 'D.' This

BUS BARS AND WIRING— GENERAL INFORMATION 401

flexibility of design will be fully appreciated if it becomes nec-
essary to make changes in the bus bar construction.

Bases. — The seven styles of bases shown in Fig. 241 will be
found to meet practically every condition encountered in the
installation of busses and general station wiring. Special bases
to meet local conditions can be supplied.

FIG. 241. — Bus bar base fittings.

Clamps. — Bus bar clamps for "Unit Type" supports are
shown in Fig. 242, Type ' I ' clamp. The type ' I ' clamp is of
the two bolt form designed to support flat copper bars in a
horizontal position on horizontal structures or in a vertical
position from vertical structures. The former method is gener-
ally used in enclosed bus bar compartments where it is essential
to limit the height of the compartment. The latter method is

FIG. 242. — Bus bar clamps for unit type supports.

more applicable to open bus bar work. Other clamps for differ-
ent purposes are available with various numbers of bolts.

Bus Switch. — The "Unit Type" bus switch shown in Fig.
14 of Chapter 1 is an interesting application of the "Unit Type"
insulators. This switch is designed to clamp directly on the bus
bar, and is a convenient method of inserting a disconnect between
the oil switch and bus, thus securing a high space factor. The

402 SWITCHING EQUIPMENT FOR POWER CONTROL

adjustable contact and holding clamps enable the switch to be so
located that a short run is secured to the oil circuit breaker
terminal. This type of switch is made for any desired capacity
flat or round bus.

Outdoor Units.— The "Unit Type" idea has been extended to
outdoor equipment for all commercial voltages. A complete
line of bus bar supports, wiring supports, disconnecting switches,
choke coils and fuse mountings have been developed.

The voltage ratings conform to the standard commercial
pressure of 6600, 13,200, 22,000, 33,000, 44,000 volts. The
following tabulation shows the insulation strength of bus bar
supports for different voltages.

"UNIT TYPE" INSULATOR CHARACTERISTICS

Normal-rated voltage Tested at Normal factor of safety

6,600 volts 30,000 volts Approx. 4 : 1

13,200 volts 54,000 volts Approx. 4 : 1

22,000 volts 75,000 volts Approx. 3 : 1

33,000 volts 100,000 volts Approx. 3 : 1

44,000 volts 125,000 volts Approx. 2% : 1

Wire and Cable. — For the main connections between the
various parts of the switch gear and the generators, feeders, etc.,
cables or wires are frequently used and most of the larger manu-
facturing and operating companies have standardized their
specifications for cables and wires. These naturally differ with
different concerns but in most cases they have been based on
specifications adopted by the National Fire Protection Associa-
tion or some similar body. In most cases two styles of rubber-
insulated braid-covered cables or wires are available: — 1. With
one weatherproof braid. These are known as Rubber-Insulated
Braid-Covered Wires and Cables. 2. With one weatherproof
braid and an outer flameproof braid. These are known as
Rubber-Insulated Flameproof Wires and Cables.

Standards. — The use of these standards in the selection of
wires and cables will greatly facilitate delivery of such wires and
cables. It will also avoid confusion due to the necessity of
following special material, and changing the dimensions of
bushings and terminals to fit special cables.

Sizes. — In order to keep the number of different kinds of
cable in an installation within reasonable limits, when the differ-
ence in insulation thickness required for different voltages is

BUS BARS AND WIRING— GENERAL INFORMATION 403

not large, it is well to use the heavier insulation for both voltages,
and to furnish a cable with more copper than is required for a
given service rather than to order a special size. Where cable
of a given size is required to have flexible stranding for some work,
it is better to use it where a stiff stranding would be satisfactory,
unless the amount of stiff stranded cable exceeds 1000 feet, so
as to warrant ordering it special for use on the installation in
question.

In ordering 600-volt, rubber-insulated wires and cables from
manufacturers' stock, specify the capacity, " National Electrical
Code Standard," and give the number of weatherproof braids
desired. For example, 61 of .1145, 600-volt Code Std. Cable
with two weatherproof braids.

Bends in Cables. — Care must be taken to see that the curve
about which the cable is bent is large enough to prevent injury
to the insulation. The radius of the smallest curve about which
bending is recommended for cables is usually given; a larger
radius is much preferable, as the larger the radius the less liability
of injury to the insulation at the bend.

Three-Conductor vs. Single-Conductor Cable. — For generator
leads, where the current is small enough to permit the use of
standard three-conductor cables, these are to be preferred to
three single-conductor cables. All cables carrying heavy cur-
rents must be rigidly supported to prevent the cables being dis-
placed by a severe short circuit.

Dry Places. — Up to and including 600 volts, single or multiple
conductor, rubber-insulated, or varnished cambric-insulated,
flameproof cables should be used. When cables are mounted
directly upon a switchboard panel, the slate or marble panel is
considered as an insulator and it is not necessary to mount the
cables upon additional insulators.

For service over 600 volts and up to and including 15,000 volts
single or multiple-conductor, rubber-insulated, or varnished cam-
bric-insulated, flameproof cables are suitable. The flameproof
covering does not provide much insulation and therefore should
be treated as a conductor and stripped back a sufficient distance
to afford ample creepage distance for the potential of the cir-
cuit. When the cable is in such short lengths that it would be
necessary to strip off nearly all of the flameproof covering to
obtain the necessary creepage distances over the surface of the
insulation, cables with weatherproof braid may be used.

404 SWITCHING EQUIPMENT FOR POWER CONTROL

Small wiring for transformers, instruments, etc., may be cleated
directly upon marble panels for circuits of not over 2500 volts, if
suitable creepage distances are provided between conductors and
to ground.

No standard has been adopted for service over 15,000 volts,
some engineers demanding full insulation for the line voltage
while others specify bare conductors.

Wet Places. — Up to and including 600-volts service single or
multiple-conductor, rubber-insulated, or varnished cambric-insu-
lated braid-covered cables can be used.

For service over 600 volts up to and including 15,000 volts,
single or multiple-conductor, paper-insulated, rubber-insulated or
varnished cambric-insulated, lead-covered cables are recom-
mended, cables to be installed without insulators.

When it is necessary to use braid-covered cables, they may be
either rubber, or varnished cambric-insulated, and must be
mounted on insulators suitable for the voltage service.

No standard has been adopted for over 15;000-volts service
some engineers demanding full insulation for the line voltage
while others specify bare conductors.

Conduits. — Metal and bitumenized fibre conduits can be used
for single or multiple-conductor, rubber-insulated, or varnished
cambric-insulated, braid-covered cables.

When single-conductor cables are used on alternating-current
circuits in metal conduits, all of the phases of the circuit must be
installed within the same metal conduit.

Metal, cement and tile conduits are suitable for single or multi-
ple-conductor, paper-insulated, rubber-insulated, or varnished
cambric-insulated, lead-covered cables.

Bells. — End bells must be used on circuits of over 2500 volts,
and should preferably be furnished on circuits of over 750 volts.

Where cables are supported on insulators below the floor (up
to and including 15,000- volt service) and there is likely tobe'mois-
ture, as on the ceiling of basements, etc., the following practice
is advisable:

Single or multiple-conductor,-paper-insulated, rubber-insulated,
or varnished cambric-insulated, lead-covered cables are recom-
mended, cables to be installed without insulators.

When it is necessary to use braid-covered cables, they may be
either rubber or varnished cambric-insulated, and must be
mounted on insulators suitable for the voltage service.

BUS BARS AND WIRING— GENERAL INFORMATION 405

Lead-Covered Cables. — In all cases, lead-covered cables are
good for continuous service with lead grounded at the maximum
voltage for which they are listed. The varnished cambric-
insulated wires and cables have insulation in accordance with the
practice of the responsible cable manufacturers. The under-
writers have not yet prepared specifications for this class of wires
and cables.

All rubber-insulated wires and cables purchased under speci-
fications of certain manufacturers, with the exception of multiple-
conductor cables, lead-covered cables, and a few special cables
are provided with a separator of cotton yarn or paper between
the rubber insulation and the copper to prevent the rubber com-
pound from adhering to the copper. This facilitates stripping
of insulation and soldering of conductors where joints are to be
made.

CHAPTER XVI

BREAKER STRUCTURES

Where the direct-control switchboard is not employed but
distant control oil circuit breakers are utilized for the main A.C.
connections, the arrangement of the breakers, disconnecting
switches, bus bars, etc., is of great importance, and on the proper
location of these devices rests the satisfactory performance of
the equipment.

Bus Arrangements. — To give a better idea of the difference
between the panel mounted and the distant control arrangements

FIG. 243.

FIG. 244.

some typical layouts of different locations for breaker and bus
are shown. Fig. 243 shows panel mounted oil breaker with
bare bus and connections for service at voltages up to 750 volts,
with bus directly over the breaker while for voltages above 750
it becomes desirable to have the bus higher than the head of the
operator. Fig. 244 shows the corresponding schemes using the
panel frame mounted breakers to get additional clearance and
to remove the breaker from the rear of the board. This panel

406

BREAKER STRUCTURES 407

frame mounting gives a better construction, in that connections
from circuit breakers to bus bars are more nearly direct and more
space is available for taking away connecting cables to panels
and for mounting switchboard details. Some of the other
advantages are the following: less likelihood of oil getting on
panels; the weight of breakers is carried on frame instead of on
panel; the rear of the panels is more accessible; several types and
capacities of breakers have interchangeable mountings; with
narrow panels the position of the breaker handle is not restricted
to the center of the panel so that knife switches and handles for
remote control breakers can often be added where this would be
impossible with direct panel mounting unless wider panels are
used.

Unit Assemblies. — In designing the bus and oil circuit-breaker
structures illustrated, endeavor has been made to assemble all
the apparatus within a unit space, in order that a section may be
considered a distinct piece of apparatus which may be located
as a unit where desired.

The enclosed and semi-enclosed structures are designed to suit
walls and barriers of concrete. In case brick structure is desired,
the dimensions may have to be modified slightly to suit the sizes
of brick used.

(a) Open Construction — Frame Mounting. — Each bus and cir-
cuit-breaker structure section with frame mounting breakers (2400
to 13,200 volts, consists of a 1^-inch pipe framework together
with necessary mounting brackets and supports for the equip-
ment, consisting of oil circuit breakers, disconnecting switches,
instrument transformers, bus bars, and connections.

(6) Open Construction — Wall Mounting. — When desire'd, equip-
ments with frame or wall mounting breakers will be supplied by
the switchboard builder with framework details omitted, and
only connections from circuit breakers to bus bars, bus bar su-
ports and terminals, wall braces, and brackets necessary to adapt
the circuit breakers for wall mounting.

(c) Semi-Enclosed Construction. — When desired, the wall
mounting or frame mounting breakers may be suitably enclosed
and barriers added between the busses, forming a semi-enclosed
structure. Such enclosures usually require a greater distance
between adjacent breakers. When the equipments are to be
installed in this manner, it is usual for the purchaser to provide
the complete cells, top slab, doors, barriers and all cell material.

408 SWITCHING EQUIPMENT FOR POWER CONTROL

(d) Enclosed Construction — Wall Mounting. — The wall mount-
ing breakers may be enclosed and separate fireproof compartments
provided for all bus bars and main connections. Equipments
with wall mounting breakers may be installed in this manner, the
purchaser furnishing all material.

(e) Enclosed Construction — Cell Mounting. — Each bus and cir-
cuit breaker structure section with cell mounting breakers, as
usually supplied includes a complete set of mounting and con-
nection details, switching and transformer equipment, and cell
mounting breakers suitable for an enclosed cellular construction,
wherein there is provided a separate compartment for each cir-
cuit-breaker pole, bus bar, and main connection. Tie rods and
channel iron base, when necessary, and breaker front cell doors
are also included. Doors for other parts of the structure can be
furnished. Structures for most of the wall or frame mounting
breakers may also be designed to line up with the cell mounting
breakers.

Frame and wall mounting breakers, 22,000 volts and over,
which are usually arranged for open construction, frame mount-
ing, are also suitable for open construction, wall mounting, and
semi-enclosed construction, wall mounting.

Cell mounting breakers, 22,000 volts and over, may be ar-
ranged for semi-enclosed construction or enclosed construction.

Floor mounting breakers are designed for open construction
and are not readily adaptable for enclosed or semi-enclosed con-
struction, although such designs are possible if desired.

Limits. — The remote mechanically controlled switchboard is
limited in capacity by physical rather than electrical character-
istics. As nearly all high capacity circuit breakers may be
arranged for remote mechanical control as well as electrical op-
eration, the problem becomes one of mechanical arrangement in
which it is usually very easy to meet the electrical requirements.

The choice of the proper form of structure for the apparatus
which is to be remote-controlled and the satisfactory arrange-
ment of the apparatus thereon presents a more difficult problem
than does the design and arrangement of the panels themselves.
The reason lies in the many practical forms of structure, and the
large number of arrangements of the apparatus which may be
made upon each of the various forms.

Equipment. — The following apparatus must usually be con-
sidered in choosing a satisfactory arrangement : Circuit breakers,

BREAKER STRUCTURES 409

bus bars and connections, rheostats, instrument transformers,
fuses for potential transformer primaries and for main wiring
when employed, and disconnecting switches. Before a proper
choice can be made, a complete diagram, including all main
wiring and all of the above apparatus, should be carefully made,
according to the system of connections which has been adopted
for the installation under consideration. From this wiring
diagram should be selected the circuit which presents the most
complications; that is, the greatest number of disconnecting
switches, instrument transformers, etc., and, with the various
practical forms of structure in mind, an arrangement should be
worked out for this unit of the structure. If the remaining cir-
cuits have the same, or a less number of members in the same
relative location in the circuit as regards the oil circuit breakers,
the problem is solved and the remainder of the work is simply
duplication. If the members in some circuits appear in other
locations than those in the circuit chosen, each differing unit
must be worked out individually, with a view, however, of
forming them into a symmetrical and uniform structure. The
choice of arrangement depends upon the capacity of the station,
the cost, the available space, the voltage, the type of circuit
breaker chosen, and the current capacity of individual circuits.

Wall Arrangement. — It should be remembered that wall
arrangement may be more costly than the separate frame arrange-
ment if large windows, which must be bridged by steel work,
occur back of the board. Concrete or masonry structures may
add considerably to the cost of floor construction and support on
account of their great weight. The wall mounting arrange-
ments occupy the least space but have the disadvantage of
giving accessibility from one side only. For this reason and
because of the great increase in available space for mounting
various members of the assembly, the separate mounted struc-
tures are preferred where space can be found.

Breaker Mountings. — There are two kinds of circuit breakers
as regards their mounting: those designed for wall or pipe frame
mounting and those for cell mounting. Any of the former may
be enclosed in cells if desired. By the latter is meant those
circuit breakers assembled from unit poles, each pole being
designed to occupy a separate cell.

Electric Control. — All the advantages gained by the use of
hand operated remote mechanical control breakers over switch-

410 SWITCHING EQUIPMENT FOR POWER CONTROL

board-mounting breakers are applicable to the electrically
operated breaker installations. The space required for breakers
and bus bars for a given capacity will be practically identical,
but due to the absence of operating rods, bell cranks, etc., arrange-
ments and designs of structures can be used that are not possible
otherwise and that present various adaptations to certain desir-
able building designs, which are out of the question with hand
operated remote control breakers. This is particularly evident
in large stations where high tension voltages such as 2400, 6600
and 11,000 are used for generators, and where extra high tension
voltages such as 22,000, 44,000, 66,000, etc., up to 150,000 are
employed for distributing circuits. The variety of structure
arrangements with electrically operated circuit breakers is
almost unlimited, but good operating practice has evolved
certain typical designs which are illustrated in the following
cuts and a brief discussion will be given for each arrangement
shown.

Structure Types. — In general it may be stated that there are
six general types of structure arrangements in use:

1. Wall mounting — All apparatus and bus bars either mounted
directly on or supported from a wall of the building.

2. Framework mounting — All apparatus and bus bars mounted
on a framework of iron pipe or structural steel shapes.

3. Combination wall or framework mounting.

4. Concrete or masonry structure mounting — all apparatus
mounted in cells.

5. Combination concrete and structural mounting circuit-
breaker in cells, with bus bars, etc., on iron framework.

6. Floor mounting and structural mounting — circuit breakers
set on floor, with bus bars, etc., mounted on iron framework.

Designs. — The illustrations show the use of the solenoid
operated circuit breakers chiefly, and have only considered
a few motor operated breakers. It will be noted that breakers of
relatively small breaking capacity and of voltages up to 13,200
and having a single frame for all poles with a single tank, have
the solenoid mechanisms fastened directly to the frame of the
circuit breaker. This makes the breaker a more or less self-
contained unit. The remaining breakers which are built with
each pole a separate unit with its own frame and tank are oper-
ated from one solenoid acting on a common operating mechanism
to which each pole is connected.

BREAKER STRUCTURES

411

Small 6600 Volts.— Fig. 245 shows typical structures for
both single-throw and double-throw bus systems, with discon-
necting switches on one side of the breaker, for installations for
voltages up to 6600 and of relatively small capacity. These

FIG. 245.

FIG. 246.

fnoNJ Vim

breakers have the self-contained solenoid mechanism as part of
the circuit breaker framework.

Small 2200 Volts. — Fig. 246 shows the next size frame breaker
which has all poles in one frame but separate tanks for each pole.
This breaker, being heavier, makes it desirable to have the sole-
noid mechanisms remote from the breaker, as shown. This type

412 SWITCHING EQUIPMENT FOR POWER CONTROL

of breaker can be used with voltages as high as 22,000 where the
total station capacity is small enough so as not to require the
use of a cell structure for the breakers.

6600- Volt Cells. — The front, rear, and side views of a struc-
ture for 3-phase, 6600-volts, solenoid operated breakers are

FIG. 248a. — Masonry compartments

for motor operated breakers.

(See Fig. 2486 and c.)

FIG. 2486.

shown in Fig. 247. The fireproof masonry compartment, bus
bars, connections, etc. are separated by shelves, walls, septums,
etc., in such a manner that no two conductors of opposite po-
larity are in the same compartment. The bus bars and laminated

BREAKER STRUCTURES

413

copper straps are supported on pillar type insulators resting on
the shelves and bent copper strap forms the connections from the
bus bars to the disconnecting switches and breakers. The dis-
connecting switches are front connected, mounted on porcelain
pillars attached to a steel base located on the rear wall of the
circuit-breaker structure.

With the type of breaker shown employing solenoid operation,
the leads are brought out at the top of the breaker tanks, taken
through the rear walls and the connections can then be run either
up or down.

i » & 'tan Minimum

_&*££***?

FIQ. 248c.

Structures for Motor Operated Breakers. — Fig. 248 shows
typical ways for arranging bottom connected, motor operated,
13,200- volt oil circuit breakers for connecting to the bus bars placed
below them, (A) back of (B), or independent of (C) structure
containing the breakers. A modification of this breaker used
particularly when the leads are to run upward has the connection
brought through the rear wall from the top of the cylindrical pots.
Where both leads are to run upwards the two pots of each pole
are arranged in tandem so that the six pots of a 3-pole breaker
are all in one continuous line.

414 SWITCHING EQUIPMENT FOR POWER CONTROL

BREAKER STRUCTURES 415

4000-Volt Installation. — Fig. 249 shows a front view, rear
view, and section of a heavy capacity 4000- volt installation with
two sets of bus bars and a double-throw arangement carried out
with two sets of disconnecting switches and one breaker per cir-
cuit. Due to the fact that the bus and breaker structure had to
be placed under an existing gallery and that the posts of the
gallery could not be disturbed, space was left between the breaker
structure and the bus structure for the gallery posts and this
space was also utilized for the generator and feeder connections.
As shown on the rear view, breakers 1 and 2 were of 1200-amperes
capacity, the breakers having oval tanks and being guaranteed
capable of rupturing 52,000 amperes at 4500 volts. Breaker No.
3 in the circuit for a 22,000-K.V.A. generator had cylindrical
tanks 20 inches in diameter and the breaker was guaranteed to
rupture 112,000 amperes at 4500 volts. As shown in the sec-
tional views for the first three breakers, connections were run up
in the opening between the breaker structure and the bus struc-
ture to one of the breaker terminals. The other terminal of the
breaker was connected by strap passing through current trans-
formers and two sets of disconnecting switches either to the upper
bus or to the lower bus. Breaker No. 4 was used for sectionaliz-
ing the lower bus. Breaker No. 5 for connecting together the
upper and the lower bus, and breaker No. 6 controlled a 12,500
K.V.A. generator. This structure has been considerably ex-
tended to control additional generators and feeders.

22,000-Volt Structure.— Fig. 250 shows a section thru the
switching galleries of a 22,000-volt installation where the genera-
tor breakers with their disconnecting switches and bus bars are
located on the second floor and the feeder circuits, duplicate
busses, and two sets of disconnecting switches are located on the
first floor. The breakers for this installation were guaranteed
capable of rupturing 5750 amperes at 25,000 volts.

Influence on Station. — While the breaker and bus structures
in certain plants can be considered independently of the balance
of the equipment in the station it is usual in large plants to give
careful consideration to the effect of the switch gear arrangement
on the entire design of the station.

In considering the effect of the structure arrangement on the
balance of the system, stations may be considered as generating,
converting, and transforming stations. In generating stations
provision has to be made for the generators with their prime

416 SWITCHING EQUIPMENT FOR POWER CONTROL

BREAKER STRUCTURES

417

movers and auxiliaries as well as for the switching equipment
which may or may not occupy much space. In converting
stations with converters or motor-generator sets the apparatus

FIG. 250. — Masonry compartments for 22000 volts.

can usually be located to better advantage and arranged to sim-
plify the wiring and switching equipment. In transforming
stations where the bulk of the power passes through step up
or step down transformers the switching apparatus can usually

418 SWITCHING EQUIPMENT FOR POWER CONTROL

be so located with respect to the transformers as to secure the
most satisfactory results. These transformer stations may be
indoor or outdoor.

Certain features of the effect of circuit breaker and bus bar
arrangement on the balance of the station can be considered to
advantage in connection with a book on switch gear in place of
one on general station design.

Locations. — In stations that distribute current at the gen-
erator voltage there are three usual locations for the oil circuit
breakers and bus bars, depending principally on the amount of
space needed for this portion of the installation. Those loca-
tions are at the end of the building, the sides of the building, or in
a separate switch house.

End of Building. — This is a favorite location for the switch gear
when the number of feeders is such that this location provides
sufficient space for the breakers and the bus bars, making due
allowance for probable future additions. With this arrangement
it is customary in large plants to provide a number of galleries for
the switching equipment. The switchboard is usually placed
on one of the upper galleries so that the switchboard operator can
readily watch the operation of the machines which he is controll-
ing.

Side of Building. — Where the end of the building does not pro-
vide sufficient space the switching equipment is frequently located
along one of the side walls, usually the side remote from the
boiler room, in a steam station or the incoming penstock in a
hydraulic station. The switching equipment when arranged in
one or more galleries along the side of the building can easily be
extended as the space available for the switch gear increases
proportionately with the space available for the generating
equipment if the building is lengthened. With this arrangement
it is usually customary to locate the generator breakers directly
opposite the individual machines and to run the bus bars the
length of the station. With this arrangement the length of the
generator leads will be reduced to a minimum and it is sometimes
possible to use bare conductors for these leads. The switchboard
itself, if electrical operation is provided, may be located either on
one of the side galleries or at the end of the building in such a
position that the switchboard attendant can readily watch the
operation of the machine which he is controlling.

Switch House. — An extension of this scheme, namely,

BREAKER STRUCTURES

419

utilizing the side walls, is to provide a separate switch house and
to control all of the apparatus electrically from a switchboard
in the main building or from a switchboard in the switch house
as preferred.

Section of Galleries. — Fig. 251 shows a section taken
through the switching galleries of a large power house, and shows
the arrangement of the oil circuit breakers, bus bars, series and

Part SectionThrough Feeder Group Switch
and at the Western End of BussesTr
Bus Tie Connections and Switch for Motor T

Section Through Generator Switches

FIG. 251. — Section of switching galleries.

shunt transformers, etc. As may be noted, the bus bars are
completely enclosed except for doors that are placed opposite
each terminal and insulator, and in front of the disconnecting
switches. This station has been in service since 1900.

As shown in the right-hand portion of the cut the generator
circuit breakers are located on the top gallery and the leads are
brought in suitable ducts to this point. The current trans-
formers for the generator circuit are located under a false floor
and the leads after passing through these transformers go into

420 SWITCHING EQUIPMENT FOR POWER CONTROL

the oil circuit breakers, and then drop down through the floor
to disconnecting switches, and to the bus bars.

In addition to the generator breakers on the top gallery,
group breakers are also installed, while on the lower gallery are
located the feeder breakers, and the bus tie breakers.

Two-phase Station. — Fig. 252 shows the front view and the
section through the switching galleries of a heavy capacity 12,300-
volt 2-phase generating station. This station contains the neces-
sary switching equipments for the control of 8-8000-K.V.A.
turbogenerators and forty feeders with a large number of local
service circuits.

The connections are so made that each generator feeds through
its own circuit breaker on to a generator bus, which generator
bus can be connected through a second breaker to two sets of
group busses, each group bus supplying current to five feeder
circuits. The generator bus bars are located directly above the
breakers in the upper gallery. The main bus bars are the top
sets on the middle gallery and the feeder group bus bars are the
lower sets on the middle gallery.

Ring Bus. — The bus structures are arranged back to back in
such a manner that the main bus bars form one continuous ring
sectioned by means of knife switches and circuit breakers while
the group bus bars can be connected to form a second ring.

The bus bars in this station consisted of four copper straps
each 3 inches by ^-inch in section per phase, these straps
being supported on suitable porcelain insulators. For the con-
nections between the circuit breakers, disconnecting switches
and bus bars copper rod of suitable size was used.

With the arrangement shown in Fig. 252, the disconnecting
switches for isolating the individual breakers are located in the
masonry compartments back of the breakers so that it is practi-
cally impossible for trouble to arise due to the station operator
pulling the wrong disconnecting switches when he desired to
inspect or repair a breaker.

Top Connected Breakers. — These last two cuts, namely Figs.
251 and 252 show one of the advantages resulting from the use
of top connected breakers with the leads brought out through
the back wall, namely, the possibility of locating the bus bars
between breakers on two different galleries.

These may be considered as typical arrangements — although
old designs of actual plants — and indicate in a general way the

BREAKER STRUCTURES

421

422 SWITCHING EQUIPMENT FOR POWER CONTROL

space allotted to this portion of the generating station in plants
of large capacity. Each installation has to be considered on its
own merits and the arrangement of circuit breakers and bus bars
is a feature meriting deep study and careful design.

Synchronous Converter Stations. — The proper grouping of the
apparatus in a synchronous converter station depends, of course,
on the voltage of the A.C. circuit, size of converter, type of trans-
formers and similar features and the building varies accordingly,
provided the shape and size of the available lot is such as not to
hamper the design of the station.

FIG. 253. — Sectional view of synchronous converter station.

Arrangement. — Fig. 253, shows the sectional view of a syn-
chronous converter substation containing 1000-K.W. 6-phase
converters with air blast transformers fed from 13,200- volt under-
ground circuits. As may be noted the incoming leads from the
cable ducts pass through an oil breaker and disconnecting
switches to the bus bars that are located on a gallery, and provi-
sion is made for an additional set of bus bars and additional
set of disconnecting switches to be installed at a later date so
that any breaker may be connected to either of the two sets
of busses.

The circuit from these bus bars passes back through other
disconnecting switches and breakers to the high tension terminals

BREAKER STRUCTURES 423

located at the bottom of the air blast transformers. The low
tension leads from the transformers go to a starting panel pro-
vided with double-throw switches that permit low voltage to be
impressed on the converter for the purpose of starting and full
voltage for running. The converters are provided with series
field on the negative side, and the negative and equalizer switches
are placed on a pedestal at the machine, and the negative and
equalizer busses run on a bracket in the basement. The positive
leads run to the panel board near the left-hand wall and the posi-
tive bus is located on the back of this board. The railway
feeders are run out through underground ducts and the entire
wiring of this station is very straight away from the high tension
incoming lines to the low tension outgoing feeders. All of the
high tension A.C. circuits are provided with electrically operated
breakers controlled from the main switchboards. The entire
design of this station hinges on the proper arrangement of the
switching equipment.

M. G. Station. — A similar arrangement of stations can fre-
quently be utilized to advantage where motor generators are
used instead of converters and the circuit breakers for the motors
can frequently be arranged along one side of the building and the
corresponding switching equipment for the generators can be
placed on the other side of the building and all of the apparatus
controlled from a single control point. With such an arrangement
the wiring is kept very straight and simple and the space is
utilized to the best advantage.

Portable Substation for Converter. — Many interurban electric
railways have portable substations located in freight cars and
arranged for ready transportation to whatever point requires
their temporary service. Fig. 254 shows a typical installation
of this kind with a 500-K.W. 6-phase converter, 2—250-
K.V.A. oil insulated self-cooling transformers and the necessary
panel switchboard, high tension oil circuit-breaker and lightning
protective devices in the 33,000-volt circuit. The general
arrangement of the apparatus, method of wiring and other details
are clearly shown in the cut. The operator standing in the
middle of the car is convenient to the commutator end of the
rotary converter.

Portable Substation for M. G. Set. — Fig. 255 shows a
similar portable substation supplied to Brazil and containing a
50-cycle, 6600-volt, 3-phase synchronous motor direct connected,

424 SWITCHING EQUIPMENT FOR POWER CONTROL

BREAKER STRUCTURES

425

to a D.C. generator. The switchboard is provided with a panel
for the self-starting synchronous motor with its exciter, a panel
for the D.C. generator and 2-D.C. feeder panels. The difference
in the type of car used is as noticeable as the difference in the
arrangement of the apparatus which they contain.

Section B-B

Section A- A
FIG. 255. — Portable substation for motor generator.

While the entire trend of American design during recent years
has been to locate transformers and high tension switch gear out
of doors, there are a few cases where, due to local conditions,
indoor equipment is utilized.

Comparison Indoor and Outdoor. — For this reason, and to
permit a direct comparison between high tension indoor and
outdoor arrangements, a number of drawings have been selected

426 SWITCHING EQUIPMENT FOR POWER CONTROL

BREAKER STRUCTURES

427

mostly of older design, showing the arrangement of hydro-
electric generating stations for various voltages from 44-K.V.
up to 110-K.V.

INDOOR STATIONS

44-K.V. Indoor.— Fig. 256 shows the plan view and Fig. 257
shows the sectional views of a generating station containing
5 — 1875 K.V.A. 3-phase horizontal shaft generators, 5 banks
each of 3— 625-K.V.A. 2300 to 44-K.V. step up transformers
two 44-K.V. outgoing transmission lines and two water wheel
driven exciters.

A panel switchboard was provided with electrically operated
breakers in the L. T. and H. T. circuits.

FIG. 257. — Sectional views 44-K.V. station.

The leads are taken from the generator as under ground cables
to the L. T. switch gear. Each generator with its bank of trans-
formers was provided with 3 — electrically operated breakers
so that the generator could be normally connected directly to
its own transformer bank, or either generator or transformer
could be connected to the transfer bus.

The transformer low tension delta bus is supported in the
framework carrying the low tension breakers with their discon-
nects. From the high tension side of the transformers leads are
taken through an oil breaker and disconnecting switches to
a 44-K.V. bus, this bus being hung from a series of suspension
insulators that are stretched between the roof girders and the
steel work that carries the disconnecting switches above the
44-K.V. breakers.

428 SWITCHING EQUIPMENT FOR POWER CONTROL

BREAKER STRUCTURES

429

430 SWITCHING EQUIPMENT FOR POWER CONTROL

From this bus, connections are taken through disconnecting
switches, breakers, disconnecting switches and choke coils to
the line outlet bushings set in the side wall. The electrolytic
arresters are of the usual type located out of doors. The par-
ticular designs shown in Figs. 256 and 257 were prepared in
December, 1909.

55-K.V. Indoor. — Figs. 258 and 259 show the plan views and
sections of a 55-K.V. station whose designs were prepared in
December, 1909. This station contains six 5400-K.V.A. 12-K.V.
3-phase generators, five banks each of three 1800-K.V.A.
transformers, 12 K.V. to 32 K.V., delta connection low tension,
star connection high tension for 55-K.V. service; two 55-K.V.
feeders, two 12-K.V. feeders, one water wheel driven exciter,
300 K.W. 250 volts, one similar exciter that can be coupled
either to a water wheel or to a motor; the motor being arranged
for coupling to either exciter.

Provision was made for grounding the neutral of the generators
by means of disconnecting switches to a neutral bus and this in
turn connecting through a grounding resistor.

All of the 12-K.V. breakers are located in a gallery above the
compartment containing the transformers and high tension
switching equipment. The generator leads are carried up the
columns that support the gallery and pass through the oil
breakers to a main bus, or an auxiliary bus, and thence back to
the low tension side of the transformers. The high tension leads
from the transformers pass through oil breakers and disconnect-
ing switches to a 55-K.V. bus that is hung from suspension insu-
lators. From that bus connections are taken through discon-
necting switches, oil breakers, other disconnecting switches and
choke coils to the line outlet bushings.

The 12-K.V. and 55-K.V. lightning arresters are arranged for
outdoor service.

The generators and main A.C. connections are controlled from
a desk while the exciter and field circuits are operated electri-
cally from the desk by means of breakers located on the exciter
and field panels.

110-K.V. Indoor. — Fig. 260 shows the arrangement of a 100
K.V. generating station using 3-phase transformers.

This plant contains two 450-H.P. horizontal shaft water
wheels, each driving a 300-K.W. 250-volt exciter, and six 9700
H.P. horizontal shaft water wheels, each driving a 7800-K.V.A.

BREAKER STRUCTURES

431

432 SWITCHING EQUIPMENT FOR POWER CONTROL

4-K.V., 3-phase generator, and six 7800-K.V.A. 3-phase trans-
formers, 110K.V.

In this plant it was the intention that the generators should
draw air in around the shaft and discharge it at the bottom of

the stator to a short duct connecting with the tailrace. With
this arrangment of discharging the heated air from the genera-
tors into the tailrace and locating the field rheostat resistors

BREAKER STRUCTURES 433

of the generator, outside the building as is sometimes done, the
question of ventilation is considerably simplified.

The leads from the generators are carried to the low tension
breaker and bus structure, thence to the low tension side of the
transformers and from the high tension side through breakers
to the high tension busses.

Alternative arrangements have been indicated locating the
lightning arrester tanks indoor and outdoor.

This station was designed in March, 1911.

Spanish Stations 110-K.V. — Fig. 261 shows a sectional view
through the 110-K.V. station at the Seros plant of the Ebro
Irrigation & Power Company in Spain, this being the first in-
stallation in Europe to operate at a voltage above 100 K.V.

The plant contains four 14,500-H.P. vertical shaft water
wheels with provision for a fifth, four 8000-K.W. 50-cycle,
6600-volt, 13,300-KV.A. generators, with provision for a fifth,
and four banks of 4444-K.V.A. 50-cycle single phase transformers
stepping up to 110 K.V. for transmission to Barcelona. Plant
was installed about 1911.

Fig. 262 shows the arrangement of the Tremp plant of the
same system installed about 1913. This plant contains four
12,500-H.P. horizontal shaft twin turbines driving 8750-K.W.
14,500-K.V.A. 3-phase generators, having transformers with
transmission lines at 110-K.V. to Barcelona and 25-K.V. from
Pobla.

The operating gallery is arranged to overlook the generator
room and the relay and recording instruments are mounted
on panels back of the control desk. Back of the relay board are
the low tension 6-K.V. circuit breakers with their bus bars and
connections.

The high tension leads from the transformers are taken up
through a floor opening to high tension breakers and then through
disconnects to the high tension bus. Connections are taken
from that bus to disconnecting switches and breakers, and thence
out to the transmission line, the arresters being located on the
roof of the building.

The high tension breakers in both of these Ebro plants have the
tandem arrangement of tanks so that all six terminals of the
3-pole breakers come in one plane.

Montana Power. — Fig. 263 shows a sectional view through
the Holter plant of the Montana Power Company, this plant hav-

434 SWITCHING EQUIPMENT FOR POWER CONTROL

BREAKER STRUCTURES

435

ing been installed about 1916. The plant contains four
16,000-H.P. vertical shaft water wheels with 12,000-K.V.A.
6600-volt generators and four 3-phase transformers with a
normal rating of 12,000 K.V.A. each, maximum rating of 16,000
K.V.A.

FIG. 263. — Sectional view Holier Plant, 110 K.V.

The leads from the generators are taken through the breakers
to the 6600-volt main bus, back from that bus through similar
breakers, or from the cross connection bus directly from the
generators to the low tension side of the step up transformers.

The leads from the high tension side of the transformers are
taken up through floor openings where they are attached between

436 SWITCHING EQUIPMENT FOR POWER CONTROL

insulators and thence through choke coils and disconnecting
switches to the high tension breakers, then to the bus and from
the bus back to other disconnecting switches, breakers and dis-
connects through roof outlet bushings.

A grounding switch is located near these roof outlet bushings
for grounding the high tension circuit, and the electrolytic
lightning arresters are located on the roof of the building.

Roof Bush I fry

FIG. 264. — Transverse section. General Station, Inawashiro Hydro
Electric Power Co.

Inawashiro. — Fig. 264 shows a transverse section through a
portion of generating station of the Inawashiro Hydro Electric
Power Company of Japan. This plant installed about 1915
contains 6-7700-K.V.A. 6-K.V., 3-phase generators, 12-4400
K.V.A. single phase transformers and two outgoing 115-K.V.
transmission lines Power is transmitted a distance of 145 miles
to Tokio where there is a receiving station whose original equip-
ment included 12-4000-K.V.A. transformers stepping down to
11 K.V. for underground distribution.

Fig. 264 shows a transverse section through the portion of
the building devoted to the transformers and the switching
equipments. The incoming penstock to the water wheel passes

BREAKER STRUCTURES 437

under this portion of the building and the warm air passing
from the generators is so arranged that it can discharge air into
the switching galleries if needed there during cold weather or it
can be discharged in such a way as to warm the lightning arrester
equipment which is located out of doors.

The transformers are placed in masonry compartments and
are so arranged that they can be pulled out into the power
house where they can readily be lifted out by the crane which
spans the generator room. The piping and valves for the water-
cooled transformers are so arranged that they can readily be
disconnected so that any transformer can be pulled out of the
compartment into the generator room at the floor level so that
it can be handled to advantage by the crane.

The relative location of the oil circuit breakers and bus bars
in the 6600-volt circuit as well as the oil circuit breakers, discon-
necting switches,bus bars and similar devices in the 115-K.V.
circuit is evident.

Path of Current. — As may be noted from this drawing the cur-
rent passes from the lower bus through the disconnecting switches
into the oil circuit breaker, out through other disconnecting
switches and current transformers to the cables carrying the
current to the low tension side of the step up transformer. The
high tension side of the step up transformer connections are taken
to the high tension delta bus and the leads are then carried up
through the floor by means of copper tubing. This copper tub-
ing is mounted on the high tension wiring support. These con-
nections then pass into the high tension breaker and through
disconnecting switches to the high tension bus. Coming back
from the high tension bus the current passes through disconnect-
ing switches into the breaker, then from the breaker through
other disconnecting switches to the line outlet bushing where
the leads are taken through the roof and are then taken through
the choke coils to the outgoing line circuit. The lightning arrest-
ers located outside the building are attached to the transmission
lines outside of the choke coils.

The supports for the bus bars and wiring in the 115-K.V.
circuit were made up of a number of insulators built into columns
corresponding to the columns used on the disconnecting switches.
These wiring supports were made of the rigid type instead of
suspension insulators, to prevent any vibration that might be
caused by earthquakes in the neighborhood of the station.

438 SWITCHING EQUIPMENT FOR POWER CONTROL

The 115-K.V. bus bars, wiring, and connections are made of
copper tubing, %-inch gas pipe size having a nominal outside
diameter of 1.04 and a nominal inside diameter of .78 inches.

This set of illustrations suggests various ways of arranging
hydroelectric plants and locating transformers and high tension
apparatus indoors. The portion of the building devoted to
transformers and high tension switch gear can be readily de-
termined and the expense of such portions of the building should
be charged against the indoor installation when a comparison is
being made between indoor and outdoor equipment.

In most cases it will be found that a considerably cheaper and
better arrangement can be made by locating the transformers
and switch gear out of doors.

A direct comparison between indoor and outdoor designs for
154-K.V. service is given later.

OUTDOOR STATIONS

While the arrangement of any outdoor station has to be deter-
mined from local conditions and the circuits to be controlled, a
series of typical layouts have been prepared to show suggested
arrangements for various voltages.

In order to cover as many different classes of arrangements as
practicable, certain figures show single phase transformers and
others three phase, some figures have water-cooled units, others
self-cooling radiator type. Various features that appear on one
figure can be utilized to advantage with the arrangement indi-
cated on others.

22-K.V. Outdoor. — Fig. 265 shows a 22-K. V. transformer and
switching station, for the control of 2-5000 K. V.A. and 4-10,000
K.V.A. 3-phase transformers feeding out over four 15,000
K.V.A. 22-K.V. transmission lines.

This station is arranged so that the high tension bus can be
sectioned in the middle, one 5000-K.V.A. and 2-10,000-K.V.A.
feeders being connected to each section. The sectionalizing of
the bus permits shutting down half of it at a time for inspection,
cleaning and repairs. By making the bus tie breaker automatic
with instantaneous tripping under short-circuit conditions and
providing the other breakers with definite time limit relays,
arrangements can be made so that only half the station capacity
will be concentrated on a short circuit.

BREAKER STRUCTURES

439

440 SWITCHING EQUIPMENT FOR POWER CONTROL

Path of Current. — The incoming low tension circuits to the
various transformers are controlled by suitable breakers in a low
tension switch house adjacent to the high tension outdoor in-
stallation. The leads from the switch house are brought as
underground cables in a tunnel to a point near the transformers
and then brought up to suitable potheads supported independ-
ently of the transformer tanks.

The high tension transformer leads pass through disconnecting
switches into an electrically operated oil breaker and pass out
through a second set of disconnecting switches to the 22-K.V. bus.
The circuit passes through disconnecting switches to the line
breaker and through a second set of disconnecting switches and
choke coils to the outgoing circuit, 22-K.V. lightning arresters
are tapped off these outgoing lines. Disconnecting switches on
each side of each high tension breaker facilitate the safe inspec-
tion of the breaker. Typical structural steel framework is
indicated for the support of the disconnecting switches and busses.
The arrangement of the steel work and the supporting towers is
diagrammatic, no attempt having been made to figure the exact
design of the various members.

While the high tension breakers are used in a 22-K.V. circuit
the illustration has been prepared on the basis of utilizing 37-
K.V. breakers to secure ample rupturing capacity for a 60,000-
K. V.A. plant. 25-K. V. breakers would be slightly smaller than those
indicated in this figure, while 50-K.V. breakers would be slightly
larger, but the general appearance of a 33 or 44-K.V. transformer
and switching station would correspond closely with Fig. 265.

66-K.V. Outdoor.— Fig. 266 shows a typical 66-K.V. trans-
former and switching station used with two banks each of 3-
2000-K.V.A., 0. 1. S. C. radiator type transformers, with one spare
transformer. This equipment is located immediately outside of
a steam generating station and the low tension leads to the
transformer banks are brought as lead-covered cable underground
and up the outside of the building. The low tension delta is
made at the transformers and a single bracket attached to the
side wall is arranged to carry the insulators for the 66-K.V. delta
connection as well as the insulator for the 13.2-K. V. delta connec-
tion.

Each transformer is on wheels, arranged so that it can be
readily rolled onto a truck and the spare transformer pushed into
its position. No provision is made by means of double-throw

BREAKER STRUCTURES

441

disconnecting switches to cut in the spare transformer in place
of any other transformer.

Each transformer bank is supplied with one electrically operated
frame mounted oil breaker connected through disconnecting

V-V NOI103S

switches to a 66-K.V. bus sectioned in the middle. This 66-K. V.
bus in turn supplies a total of 4-66-K. V. outgoing feeders through
disconnecting switches and oil breakers. Line suspension choke
coils are connected into the outgoing feeder circuits and electro-
lytic lightning arresters are tapped off of these circuits. The oil

442 SWITCHING EQUIPMENT FOR POWER CONTROL

circuits breakers indicated on this drawing are the 400-ampere,
73-K.V. frame mounted breakers. This layout is based on that
of an installation in the Middle West.

88-K.V. Outdoor.— Fig. 267 shows a typical 88-K.V. outdoor
switching equipment used in connection with two 7000-K.V.A. 3
phase, oil insulated, self-cooled radiator type transformers.
There are two high tension incoming lines connecting through

FIG. 267. — 88 K.V. outdoor switching station.

disconnecting switches and oil breakers to a high tension bus,
sectioned in the middle by means of a breaker. Each section of
bus connects in turn by disconnecting switches and a breaker to
the high tension side of a 7000-K.V.A. transformer.

The 6.6-K. V. side of each transformer connects through discon-
necting switches and oil breakers to a low tension bus that is also
sectioned in the middle. This 6.6.-K. V. low tension bus supplies
current to four 6.6-K.V. outgoing feeder circuits. For this
installation the low tension breakers and busses as well as the

BREAKER STRUCTURES

443

high tension breakers and busses have been shown as being of the
outdoor type.

The oil circuit breakers indicated for use in the 88-K.V. cir-
cuits, are the 400-amperes, 95-K.V. breakers.

The disconnecting switches in the 88-K.V. circuits are of the
normal inverted single-pole type to be operated from the ground
by means of a long pole.

110-K.V. Outdoor. — Fig. 268 shows in plan view, a typical
110-K.V. outdoor transforming station used for the control of

FIG. 268. — Plan view 110 K.V. outdoor station.

4 — 110-K.V. transmission line circuits and six banks of trans-
formers, each of 3 — 5000-K.V.A., O. I. S. C. radiator type units.
The arrangement shown is a slight modification of an actual
installation that has been operating in the South for a number of
years, and the location and type of disconnecting switches
corresponds with those in service.

For this station all of the low tension switching is controlled
by means of breakers located in a low tension switch house
adjacent to the high tension transformer yard.

Section. — The high tension leads from each transformer, as
shown in Fig. 269, are taken through disconnecting switches to
a 115-K.V. round tank oil breaker. The leads from the trans-
former oil breakers then pass through other disconnecting

444 SWITCHING EQUIPMENT FOR POWER CONTROL

switches to the 110-K.V. bus at the same time tapping across
to the disconnecting switches and breakers for the outgoing
line circuits.

The two sets of 110-K.V. bus bars, one on each side of the
railway transfer track can be connected by means of the oil
breaker in the outer row at the right center as shown by section
B.B.

This installation contemplates 4 — 110-K.V. line circuits and
to reduce the cost of the arrester equipment each pair of lines,

To low Tension Switch House

To low Tension Snitch Hov

Section BB
FIG. 269. — Section view 110 K.V. outdoor station.

which normally operate in parallel is provided with two sets
of horn gaps, but only one set of arrester tanks with their oil,
trays and electrolyte.

Disconnecting switches of the inverted single-pole type, pole
operated, or of the inverted or upright, multiple pole, mechanic-
ally operated type can be substituted, if desired in place of
those shown, and would usually be considered preferable, owing
to the inherent weakness of a long heavy porcelain column in a
position of a practically horizontal cantilever beam.

132-K.V. Outdoor. — Fig. 270, shows in plan view, a typical
132,-K.V. transformer and switching station. In this station,
there are two banks, each of 3— 10,000-K.V.A., single-phase

BREAKER STRUCTURES

445

transformers, 11-K.V. low tension voltage, 132-K.V. high tension
voltage with 2 — 132-K.V. outgoing transmission lines running up
the side of the hill. This arrangement is based on the Windsor
installation of the West Penn Power Company.

In this installation, the low tension leads are brought from the
adjacent steam generating station in a cable tunnel to the trans-
formers. The high tension transformer leads are carried over
head between strain insulators and taps are taken down from

Fio. 270. — 132 K.V. outdoor switching station.

these cross connections to the breakers and the current passes
through disconnecting switches and breakers to the transmission
line or can feed back through other disconnecting switches and
breakers to a high tension transfer bus.

Provision is actually made in this plant for tieing together this
transformer yard feeding one distributing system with its two
30,000-K.V.A. transformer banks to another transformer yard
of slightly larger capacity feeding a different transmission
system.

The disconnecting switches used for isolating the oil breakers
are of the inverted type for pole operation. On the outgoing

446 SWITCHING EQUIPMENT FOR POWER CONTROL

line breakers, a combination choke coil and single-pole discon-
necting switch is utilized. As part of the lightning arrester
equipment, mechanically operated 3-pole rotating type,
double-break disconnecting switches with an auxiliary grounding
device is furnished. Mechanically operated 3-pole disconnecting
switches are usually preferable to any other type for voltages
higher than 88 K.V. in so far as operation is concerned, but they
normally require more elaborate steel structures to permit their
satisfactory use.

Comparison Indoor and Outdoor. — To give a concrete com-
parison of transformer and switching stations for indoor and
outdoor service at 110 K.V. and 154 K.V. Fig. 271 and Fig.
272 have been prepared to show typical arrangements in a large
capacity water power plant to contain 6 — 22,500-K.V.A. genera-
tors, 6 banks each of 3 — 7500-K.V.A. single-phase step up trans-
formers and 4 — 45,000-K.V.A. transmission lines. The portion
of the building intended for the generators has been drawn up for
both horizontal and vertical shaft units.

Indoors. — Fig. 271, shows the generating station with indoor
transformers. On this drawing Fig. 1 shows a sectional view
through the transformer and switch building to show the general
location proposed for the transformers, oil circuit breakers,
disconnectings switches, bus bars, lightning arresters and other
apparatus. This portion of the drawing as well as the balance
of the drawing has been made to scale showing the devices needed
for the 154-K.V. installation. Two sets of dimensions have been
marked in certain places, one giving the overall dimensions for
154-K.V. service, the other for 110-K.V. service.

Section. — As shown in the sectional view, Fig. 2, the 11-K.V.
oil circuit breakers and bus bars are located back of the trans-
formers, transformers being on wheels to permit their being
readily rolled out into the generating station where they can be
handled by the overhead crane.

The high tension leads from the transformers are taken up
through floor openings and are mounted on suitable supports.
These supports, as well as the piller supports for the disconnect-
ing switches for indoor service, will probably be made of micarta
tubing although possibly porcelain insulators built up in suitable
columns may be employed.

The high tension neutral is run in the same compartment as
the transformers.

BREAKER STRUCTURES

447

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448 SWITCHING EQUIPMENT FOR POWER CONTROL

The phase leads from the transformers after passing up through
the floor openings go into the oil circuit breaker. From the oil
circuit breaker they are taken through either of the sets of dis-
connecting switches to either of the two high tension busses.
These high tension busses are suspended from the roof trusses
in the manner indicated. These bus supports will probably be
of the suspension insulator type although they may be a rigid
built-up porcelain column, or possibly micarta tubing supports
will be utilized.

From the busses the leads are taken back through the discon-
necting switches through the oil circuit breaker, then to the line
disconnecting switch, the roof bushing, choke coils, and thence
to the high tension line.

The lightning arresters with their horn gaps, transfer switches
and arrester tanks are located on the roof of the building.

Section at Centre. — On this same drawing, Fig. 2 is a section
taken at the center of the building to show the location of the
bus junction oil circuit breakers on the high tension gallery, the
control desk, local service board and battery room on the mez-
zanine gallery, the field and exciter board and rheostat resistors
on the lower floor.

Space Requirements. — A space the entire length of the generat-
ing station 320 feet long, has been allotted to the transformers
and switching equipment.

For the 154-K.V. arrangement this portion of the building
will have a height of 76 feet and a width of 44 feet, allowing about
6 feet between phases and 4 feet to ground.

For the 110-K.V. proposition allowing 5 feet between phases,
3 feet to ground, the portion of the building devoted to trans-
former and switching equipment would have a height of 64 feet
and a width of 36 feet.

Plan H.T. Room. — Fig. 3 shows a plan view of the high ten-
sion switching room. As may be noted, the high tension oil
circuit breakers are arranged in a row near the wall between the
transformer house and the generator house, while the bus bars
have beeen shifted slightly towards the outside wall of the
building.

Space has been left available so that if desired breakers and
disconnecting switches for two additional lines can be readily
installed, one at the extreme right hand and one at the extreme
left-hand end.

BREAKER STRUCTURES 449

The tie breakers as well as the bus junction breakers are located
near the central portion of the high tension switch room.

The high tension bus bars in addition to being suspended from
the roof trusses as shown in the sectional view are held by strain
insulators at each end of the building to minimize vibration.

Plan Main Floor. — Fig. 4 on this same drawing shows the plan
view of the main floor of the power house using horizontal shaft
water wheel generators and making the transformer house inte-
gral with the generating station. A note is placed on this Fig. 4
showing the location of the station wall if outdoor transformer
and switch yard is used.

The various transformers have been indicated as being in
transformer compartments, so arranged that any one trans-
former can be readily rolled out on its wheels to a point where it
may be lifted by the traveling crane.

Outdoor Layout. — Fig. 272 shows outdoor transformer and
switch yard. This drawing which has been made to scale show-
ing the 154-K.V. installation has, in most places, two sets of
dimensions, one giving the dimensions for the 154-K.V. installa-
tion, and the other for the corresponding 110-K.V. installation.

Plan View. — The bottom portion of the drawing shows the plan
view location, the transformer bank, the four outgoing lines, the
bus tie and junction circuits and similar main features.

Longitudinal Elevation. — On this plan view a center line marked
'EEE' has been placed to show where the longitudinal eleva-
tion has been taken. This longitudinal elevation has been taken
in such a manner as to show most of the important features,
such as the horn gaps, the arrester tanks, the transformer banks
with their neutral connections and neutral busses, the transformer
oil breaker, the framework and supports for the selector type
switches in the transformer and line circuits, the junction breaker,
tie breaker, etc.

Line Equipment. — On the upper portion of the drawing, sec-
tion 'A A' shows the line equipment. As may be noted, con-
nections are taken from the bus bars to short leads that are
stretched between strain insulators attached to the lower frame-
work and to the supporting framework of the selector switches.
The leads pass thence to the outside studs of the selector switches
and from the central studs to the wires that are held by the
strain insulators attached to the tower structure. From these
wires, the leads drop to the line breaker and from the line breaker

450 SWITCHING EQUIPMENT FOR POWER CONTROL

BREAKER STRUCTURES 451

to the line disconnecting switch and choke coils, to the outgoing
line circuit. The horn gaps, transfer switch and arrester tanks
of the arrester appear on this sectional view.

Transformer Equipment. — Section at 'BB' shows the trans-
former equipment and shows how the high tension lead passes
from the transformer to the oil breaker, from the oil breaker to
the wire that is stretched across the strain insulators attached
to the tower framing. From this wire the leads pass to the
central stud of the double-throw disconnecting switch. The
outer studs of these switches are connected up to the busses in
the manner shown.

Bus Connection. — Section at 'CC' shows the bus cross con-
nections while section at 'DD' shows the bus tie arrangement.

Neutral Resistor. — With the outdoor equipment as shown on
Fig. 272 the neutral grounding resistors will have to be housed in
as they are not suitable for exposure to the weather The en-
closure for the grounding resistor is made a portion of the central
tower, and a suitable roof bushing is furnished for taking in the
leads from the neutral bus to the grounding resistor.

Steel Work. — The steel work for the tower construction has
been shown in merely typical form and the dimensions and spac-
ings are more than ample. It is quite probable that a more
detailed design of this outdoor transformer and switch yard
would permit decreasing the height of the structure and possibly
shortening up the width of the various spans.

This drawing, however, gives a fairly clear idea of one manner
in which the transformers and switching equipment could be
arranged for outdoor service to advantage.

Space Needed. — As may be noted, the tower construction for
the 154-K.V. installation occupies a length of 524 feet on centers
with a width of 80 feet, while the corresponding dimensions for
the 110-K.V. equipment are 430 feet length and 86 feet in width.
The height of the high towers will be 74 feet for use of the 154-
K.V. installation, 60 feet for the 110, while for the shorter towers
these dimensions will be 62 feet and 50 feet respectively.

It is considered quite probable that these heights may
be reduced from 5 to 10 feet as the result of the closer
calculations.

Cost of Building. — With the arrangement shown of Fig. 272 the
space required for housing the transformers and switch gear for
the 110-K.V. arrangement was 320 feet long, 64 feet high, 35 feet

452 SWITCHING EQUIPMENT FOR POWER CONTROL

BREAKER STRUCTURES 453

wide or a total of about 735,000 cubic feet. On the basis of
twenty cents per cubic foot, this would cost about $150,000.

On the same basis, the corresponding portion of the station
required for the 154-K.V. layout would have a cost of about
$225,000.

The cost of the steel work erected, and the extra cost of making
the 110-K.V. A apparatus suitable for outdoor service in place of
indoor would amount to about $60,000 showing a net saving
of about $90,000 for using outdoor equipment, while for the
154-K.V. proposition the net saving would be about $135,000.
These figures are about 13 percent of indoor costs.

Figs. 273 to Fig. 276 shows the arrangements proposed for a
typical 220-K.V. outdoor switching and transformer station.

Diagram. — A single line diagram, Fig. 273 shows the main
connections proposed for this plant, that is to contain 4-50,000-
K.V.A., 220-K.V. outgoing transmission lines. As shown in
this single line diagram of connections, each generator with its
transformer bank is provided with a total of three oil breakers
with suitable disconnecting switches. The connections are so ar-
ranged that while normally each generator will tie in with its
own transformer bank, any generator or transformer bank can
be connected to the low tension transfer bus.

Switches and Breakers. — On the high tension side of the trans-
formers the electrically . operated, 3-pole disconnecting
switches are provided with electrically operated breakers in the
outgoing line circuits. Normally each transformer bank will
be connected to its own outgoing line breaker but by means of
the electrically operated disconnecting switches any transformer
bank or any line breaker may be connected to the high tension
transfer bus. The disconnecting switches were made electri-
cally operated to facilitate their control from one central point.

Plan. — The plan view arrangement Fig. 274 shows the relative
position proposed for the transformer banks, disconnecting
switches, oil breakers, arresters, etc. While the elevation sec-
tion 'FF' shows somewhat more clearly the general relative
location of these various devices.

Section. — The disconnecting switches shown in sectional view
Fig. 275 have special insulator columns, each pole of a discon-
necting switch normally requiring three columns. One supports
the stationary contact and stationary arcing horn ; one acts as a
brace pillar, and the third is arranged to rotate in such a manner

454 SWITCHING EQUIPMENT FOR POWER CONTROL

as to secure a vertical rotation of the switch blade and movable
arcing horn.

As indicated in the plan view, the two 3-pole disconnecting
switches adjacent to the transformer banks have their poles
alternated and the two poles in any one phase have a common
brace pillar, so as to reduce the number of insulator columns.

The disconnecting switch located near the oil breaker has each
pole provided with its own set of three insulator pillars. The
disconnecting switch used with the arrester horn gaps has its
break jaw and stationary horns indicated as being mounted
directly on the terminal of the oil circuit breaker.

The lightning arrester horns are mounted on similar pillar
insulators and the central pillar carries a combination horn and
transfer switch.

Elevation. — As shown particularly in the side and end eleva-
tion Fig. 276 the oil breakers in the 13.2-K.V. circuits are indoor
breakers, these being located inside the hollow platform on
which the insulators of the 220-K.V. disconnecting switches are
mounted. These breakers are provided with suitable disconnect-
ing switches and are arranged to tie onto a low tension transfer
bus or connect a transformer direct to a generator as desired.

The low tension transformer leads in the form of copper strap
are taken from the transformer delta bus out through the side
wall of the concrete platform.

The path of the high tension connections from the transformer
terminals through the disconnecting switches on the platform
to the high tension bus or to the line breakers can be readily
followed from the figure.

The oil breakers contemplated for this installation are 220-K.V.
circular tank type breakers.

While the high tension disconnecting switches have been indi-
cated as being operated by the rotation of one of their pillars, a
somewhat different type of mechanism may be employed and
the switches themselves instead of being mounted on concrete
platforms may be located on steel structures.

These various drawings indicate typical methods of arranging
large capacity outdoor transforming stations. Moderate capa-
city high voltage stations could be arranged in a somewhat
simpler manner.

INDEX

Air break circuit breakers, see car-
bon breakers.

Altitude effect on oil circuit break-
ers, 76, 77

Ammeter switches, 8, 9, 10
Ammeters, see Instruments.
Automatic circuit breakers, see Car-
bon Breakers or Oil Circuit
Breakers,
overload trip, 88
protection, A.C. generators, 25
D.C. generators, 24
differential protection, 25,

167

exciter and field, 24
feeder circuits, 26
motor-generators, 307
synchronous converters, 25
starting, 260, 265
substations, G. E., 336-343

Westinghouse, 343-350
Auto-reclosing circuit breaker, 46,

49, 310

Autostarters, 264
Auto-transformer starting, 264

Battery charging generator section,

297
panels, 296

and generator panels, 303
and lighting panels, 302
rheostat, 297

switchboard assembly, 297
location, 298
platform, 298
Bevels on panels, 282
Breaker, see Carbon Breaker or Oil

Circuit Breaker.
Bristol meters, 176

Brooklyn Rapid Transit Co. Control

Desk, 375, 376, 377
Bus arrangements, 406
Bus bars, 381

for A.C. service, 381

for D.C. service, 381

capacity, 383

compartments, 383
brickwork, 384
concrete, 384
shelves, 384

enclosures, 385

extra high tension, 388

fittings, 398

laminated type, 386

material, 382

open construction, 388

stresses, 386, 389, 396

supports, 394-400

switch, 401

systems, 270-273, 382

Cables, 391
bells, 404
bends, 403

for auxiliary apparatus, 391
for control and instrument wir-
ing, 391

for dry places, 403
for wet places, 404
load covered, 405
3 conductor vs. single conduc-
tor, 403

Carbon breakers acceleration, 42
attachments, 42-45
auto-reclosing, 46-49, 310
bell alarm, 45
Condit, 49-51
construction, 39
contactor, 71
contacts, 40

455

456

INDEX

Carbon breakers, current ratings, 38
Cutter— I. T.E., 51-60
desirable features, 37
distinctive features, 39
double arm, 45
electric operation, 41
electro-pneumatic control, 60
field discharge, 45
General Electric, 60-65
historical, 36
interrupting capacity, 38
inverse time, 43
manual operation, 41
method of operation, 40
motor operated Cutter, 54-67

G. E., 64
overvoltage, 44
pneumatic operated, 59
relays, 45
reverse current, 42
Roller-Smith, 65-66
shunt trip, 43
signals, 44
solenoid operated Cutter, 57-

G. E., 64
Westinghouse, 74
space requirements, 37
temperature, 38
trip-free, 45
tripping, 42
underload, 44
undervoltage, 43
Westinghouse, 66-74

Choke coils, 219

Circuit breakers, see Carbon Break-
ers or Oil Circuit Breakers,
fused, 33
Schweitzer-Conrad, 34

Code fuses, 28

Code rule for three-wire panels,
314

Combination generator and feeder
panels, 304

Comparison, indoor and outdoor lay-
outs, 425, 446

Comparison methods of three-wire
control, 314, 315

Condit carbon breakers, 49-51

Condit instrument transformers,

200-202

oil circuit breakers, 90-107
Conduits, 404
Connection, diagrams,

ammeter switch, 10
automatic acceleration from

counter e.m.f., 261
with series relay, 260

substations, G. E., 338

Westinghouse, 344
auto-reclosing circuit breaker,

auto starter, 264
balanced system of relays,

163

charging panels with magnet-
ically operated switches,

301
compensator connections for

regulator, 250
cutter three-wire generator,

325
D.C. starter with low-voltage

release, 259

double bus system, 271
excess voltage protection for

regulator, 252

exciter and field circuits, 361
face plate controller, 257
G. E. voltage regulators, 243
generator and battery panel,

304

glow-meters, 184
impulse gap, 217
M.G. sets for mine service,

307
motor operated circuit

breaker, 56

mutually reactive coils, 226
railway, 1500-volt, D.C., 335
ring arrangement of circuits,

161

Rio de Janeiro, 273
Schweitzer-Conrad multi-cir-
cuit relay, 167

recording synchronoscope,

178
single bus system, 270

INDEX

457

Connection, Solenoid operated cir-
cuit breaker, 58
switchboard A.C., 440 volts,

318

synchronizing, 11, 12
synchronous converters for

mine service, 312
temperature indicating de-
vice, 189
three-wire generators, 313

synchronous converter, 312
transfer type relay, 166
typical generator and bus,

268
typical plant with sectioned

bus, 272

wattmeter switch, 10
welding panels, 316
Westinghouse voltage regu-
lator, 246

Connections, 385, 390
Contactors, 254-5
Control desk, 375

relays, 16
Controller, 255

drum type, 257
face plate type, 256
Converters and M.G. sets, 328

Delta-Star bus fittings, 398
fusea, 31, 32
switches, 19
Desk, 375

for Brooklyn Rapid Transit Co.,

375-377
for horizontal edgewise meters,

378
for round pattern meters,

379-380
for vertical edgewise meters,

378-379

Diagram of connections, see Con-
nection Diagrams.
Differential protection, 25
Direct control oil breakers, 363
Disconnecting switches, 17, 18,

19, 20
fuse, 30

Drum switches, 9
Duncan meters, 176

Edison battery charging, 301
Electric remote control oil circuit

breaker, 363
Electrolytic lightning arrester, see

Lightning Arrester.
Engine generator protection, 328
Esterline instruments, 176
Exciter automatic protection, 24

panels, 360

regulators, see Regulators

Feeder protection, see Protection.
Feeders in automatic substation, 346
Field discharge switches, 5, 360

protection, 24. See Protection.

transfer switch, 6
Finish marine, 281

oil, 281

Flexibility, 274

Frames for switchboards angle, 279
pipe, 279
small panels, 282

Frequency meters, see Instruments.
Full automatic, 88
Fuse blocks, switchboard type, 29

circuit breakers, 33

indicators, 28

limitations, 28

switch, 31
Fuses, Delta-Star, 32

disconnection switch type, 30

enclosed type, 28

expulsion type, 27

General Electric type, 32

National Electrical Code, 28

oil type, 30

open type, 26

Schweitzer-Conrad, 30

transformer type, 29

General Electric Co., carbon break-
ers, 60-65
control switch, 13

458

INDEX

General Electric Co., disconnecting

switches, 19
fuses, 32

instruments, 175-176
A.C. watt-hour meters,

176
D.C. watt-hour meters,

175
horizontal edgewise type,

175

round pattern, 175
oil circuit breakers, 108-

124
heavy capacity type

"H," 114-119
high-voltage type

"K," 119-124
industrial, 108
low-voltage modern

"K," 110-114
old "K," 110
pole line, 109
textile, 109

Generator protection, 25. See Pro-
tection.

Ground connection, 210
detector switches, 8
detectors, 184

Hand-operated remote control oil

breakers, 363
High-voltage A.C. switchboards,

318-320

Horn gap arresters, 220
choke coils, 220
switches, 20-23

Inawashiro control desk, 379-380
field switchboard, 352
station layout, 436
Indicating meters, see Instruments.
Indoor station layouts, 115
Inawashiro, 436
44 KV., 427
55 KV., 428-430

Indoor station layouts, liO KV.,

430-433
110 KV., Spanish stations,

432-434
110 KV., Montana Power

Co., 435

Influence switchgear on station de-
sign, 415
Instrument switches, 7

transformers Condit, 200-202
current, 198
double secondary, 206
functions, 198-199
General Electric, 202
makers, 200
oil immersed, 199

insulated current, 206

potential, 207
outdoor metering, 207-208

type, 206
precautions, 199
relay transformers, 204
through type, 205
Instruments, A.C., 172

ammeters, 173, 185
induction, 172
moving coil, 172

iron, 172
voltmeter, 172
Bristol, 176
D.C. ammeters, 172

voltmeters, 172
demand type, 185
Duncan, 176
eclipse, 192
exploring coils, 189
field ammeter, 173
frequency meter, 174, 183
glow meters, 184
graphic meters, 174, 186
illuminated dial, 183
power factor meters, 173
recording synchronoscope, 177-

179

relay type, graphic, 187
Roller-Smith, 177
Sangamo, 176
Schweitzer-Conrad, 177
static ground detector, 174

INDEX

459

Instruments, static ground detector,

174
synchronoscope, 177, 182,

194

temperature indicator, 189
thermo-couples, 190
watt-hour meter, 173, 175
Westinghouse, 179-191
A.C. meters, 181
D.C. large meters, 180-181

small meters, 179-180
synchronoscope, 182
Weston, 192-197
edgewise type, 193
frequency meter, 196-197
power factor meter, 195-196
synchronoscope, 194-195
Integrating watt-hour meters, 185
Inverse time, 89
Isolated plant switchboards, 326
I.T.E.— Cutter circuit breakers, 51-
60

Knife switches, 1

Lamp indicators, 16
Lead battery charging, 301
Leads in structure, 385
Lightning, 209

arrester choke coils, 219
condenser type, 212
D.C. service, 211
electrolytic, 214-216
gaps, horn type, 216
impulse type, 217
speed, 218
sphere type, 217
horn type, 220
multi-chamber, 213
multipath, 211
non-arcing type, 212-213
oxide film, 219
Railway & Industrial Eng.

Co., 220-223

Schweitzer & Conrad, 222-223
direct strokes, 209
displaced neutral, 210

Lightning, good ground, 210

induced strokes, 209
Locations for structures, 418
Lockout contactor, 263

features automatic substation,

349
Low voltage A.C. switchboards, 317-

318, 361-362

protection for battery charg-
ing, 300

release for starter, 258
in mines, 309

Marble, 280

blue Vermont, 280
Material, 280
Meters, see Instruments.
Mining switchboards, 306

for engine generators, 306
for feeders, 308
for motor generators, 307
Motor driven rheostat, 352

switch, 64
starters Condit, 90, 95

Westinghouse, 130
Multiple multipole breakers, 127,

133
switch starter, 259

National Electric Code fuses, 28
Neutral lead three-wire generators,

326

Nickel — iron battery charging, 301
Non-automatic circuit breakers, 88

Oil circuit breakers acceleration, 87

A.C. control, 85

altitude effect, 76

application, 75, 80

automatic recommenda-
tions, 83

calibration, 89

Condit, 90-107

control circuit, 86
voltage, 87

direct control, 84

460

INDEX

Oil circuit breakers, distant control,
84

effect of regulators, 81

electric control, 85

features, 75

General Electric, 108-124

guarantees, 84

indicators, 85

inverse time, 89

manual control, 84

mechanism, 86

methods of trip, 88

overload trip, 88

rating, 76-78

series trip, 89

short circuit curves, 80

time of trip, 81
relays, 83

transformer trip, 88

Westinghouse, 124-156
Old panel switchboard, 277
Ontario Power Co., 374
Outdoor station layouts, 22 K.V.,
438-9

66 KV., 440-1

88 KV., 442

110 KV., 443-4

132 KV., 444-6

154 KV., 446-453

220 KV., 453-4
Overload protection battery panels,

299

relays, see Relays,
trip, 88

Overvoltage relays, see Relays.
Oxide film arresters, 219

Panel bevels, 282

frame mounted oil circuit break-
ers, 364

switchboards for D.C. genera-
tors and converters, 321
Panels, combination generator and
feeder, 312

exciters, 360

1500 volt railway, 332, 334

for three-wire service, 313

for welding, 315, 317

Pedestals, 372-374
Plug switches, 7

Polarity control of automatic sub-
stations, 345
Portable substations, 350

for motor generators, 423, 425
for rotaries, 423, 424
Posts, 373, 375
Potential regulator, 233-253

transformer, see Instrument

Transformers.
Power control sections battery

switchboard, 299
factor indicator, see Instru-
ments,
switchboard, General Electric,

322

Pittsburgh Electric, 323, 324
Protection automatic substation
against A.C. overload,
348

D.C. overload, 348
low voltage, 347
overheating, 341
overload, 341
overspeed, 349
polarity reversal, 348
reversal, 341
reverse current, 349
short circuit, 341
temperature, 348
Protection synchronous converters,

331

three-wire panels, 314, 325, 329
two-wire panels, 329

Quick break switches, 2

Railway & Industrial Engineering

Co., arresters, 220, 222
switches, 20-23
Railway switchboards, 321
Reactors, cast-in, 227

General Electric, 226-229
makers, 224

Metropolitan Engineering Co.,
224-226

INDEX

461

Reactors, multiple winding, 230
mutually reactive, 225
porcelain clad, 225
semi-porcelain clad, 226
three-phase type, 231
Recording meters, see Instruments.
Regulators, application, 247

auxiliary exciter rheostats, 251

battery control, 252, 253

compensation, 249

condensers, 250

excess voltage device, 251

exciter rheostats, 251, 252

flicker, 248

General Electric Type, 242-244

generator, 241-253

master relay, 245

parallel stations, 250

rheostat shunting relays, 247

single operation of exciters, 249

Tirrill, 242

vibrating relay, 245

voltage adjusting rheostat, 249

rise, 251

Westinghouse, 245-253
Regulator feeder induction, 234

motor drive, 237

no voltage device, 238

outdoor type, 238

polyphase type, 236

primary relay, 238

regulator limit switch, 238

single phase, 235

step type, 233
Relays, A.C. definite time, 157, 160

overload, 159
balanced system, 162

type, 162
bell, 166

characteristic curves, 160
definite time, 157, 169
D.C. overload, 157

reverse, 158
double contact, 164

high tension, 170
multi-circuit, 167
parallel system, 161
ring system, 161
series, 168

Relays, split conductor, 162

temperature, 164

transfer, 165
Resistors for rheostats, 241

for starting, 258
Reverse protection battery charging,

300

motor generators, 309
Rheostats, 239-241

battery charging, 297

distant control, 240

motor operated, 240

resistors, 241

solenoid control, 240

1500 volts, B.C., 334
Roller-Smith carbon breakers, 65-66
instruments, 177

Safety code, 295
Sangamo meters, 176
Schweitzer-Conrad circuit breaker,

fuses, 30, 31, 32
multi-circuit relay, 167
Series trip, 89, 127
Shipment of switchboard, 280
Short circuit characteristics, 79

curves, 80

Shutting down automatic substa-
tions, 340, 347
Slate, 281
Standards, 276
Starters, A.C., 263
automatic, 260
auto-transformer, 264
counter e.m.f., 261
D.C., 258

electric operated, 260
flywheel set, 266
mill work, 266
mine motors, 308
multiple switch type, 259

phase wound motors, 265
series lockout, 262
squirrel cage motor, 263
synchronous motor, 265
wound rotor motor, 263

462

INDEX

Starting automatic substations,

General Electric, 339
Westinghouse, 343

combinations, 308

converters from A.C. end, 332,

357
from B.C. end, 330

switch, 332

Station layouts, see Indoor Station
Layouts and Outdoor Sta-
tion Layouts.
Supports for tubing, 390
Switch, ammeter, 8

control, 12

Delta-Star, 19-20

disconnecting, 17-20

drum, 9

field discharge, 5

field transfer, 6

front connection, 3

fuse shunted, 32

fused, 31

galleries, 419

General Electric, 19

ground detector, 8

house, 418

horn break, 20

instrument, 7

knife type, 1

motor starting, 5

Plug, 7

rear connection, 3

safety, 6

synchronizing, 9, 11

voltmeter, 8, 11

wattmeter, 11
Switchboards, A.C., 286
blank panels, 362
connections, 267
with knife switches, 317, 361
oil circuit breakers, 319, 363

A.C. instruments, 293

ammeter scales, 291

angle iron frame, 279

battery charging sectional, 296
bevels, 282

bracket instruments, 294

bus taper, 288

carrying capacity, 289

copper, 289, 290

Switchboards, D.C., 286

connections, 267

electrically operated, 351

heavy capacity Al. Co. of
America, 353, 354

instruments, 293
desks, 288
diagrams, 267
direct control, 284, 287
distant control, 287
double bus, 271
early panels, 282
electrical control, 287
equalizer bus, 290
exciter bus, 290
feeder instruments, 294
field ammeters, 293

and exciter, 351
flexibility, 274
Ford Co., 355-357
frame, 282
General Electric D.C., 323, 355

panel sections, 283
ground detector, 294
Inawashiro, 353
indicating wattmeters, 293
instrument transformers, 270
instruments, see Instruments,
interrupting capacity, 292
largest builders, 274
location of bus, 289
marble, 280
marine finish, 281
material, 280
mining, 306
oil circuit breakers, 292

finished, 281
old panels, 277
panel rating, 291

sequence, 288

type G. E., 366

Westinghouse. 365
panels, 288

pipe frame, 279
posts, 288

present standards, 278
ratings, 292
remote control. 287
requirements, 286

INDEX

463

Switchboards, rheostats, 294
ring bus, 271
Rio de Janeiro, 351
safety code, 295
sectioned bus, 272
shipping, 280
single bus, 270

line diagram, 267
slate, 281

vs. marble, 281
small panels, 281
special bus, 273

panels, 285
standard panels, 285
standards, 276
switching apparatus, 292
temperature rise, 291
truck type, 368-370

construction, 369

contact jaws, 370

covers, 370

interlocks, 370

limits, 369

mounting, 370

tubing carrying capacity, 290
typical connections, 268
ultimate bus capacity, 290
wooden board, 276
Synchronizing switches, 8
Synchronoscopes, 174, 182, 194
Synchronous converter stations, 422

Temperature relays, 164

Thermostat, 349

Three-wire Cutter breakers, 325

control electrically operated,

325
Time element for starting breaker,

309

Top connected breakers, 420
Torque compensator, 160
Transfer relays, 165
Transformer, current, see Instru-
ment Transformers,
fuses, 29
panels, 331

potential, see Instrument Trans-
formers,
trip, 88, 127

Tripping, calibration, 89
Truck panels, 368-370
Tubing for bus, 390

Underwriters requirements for wir-
ing, 391

Union Electric Light & Power Co.,
372

Voltage readings, A.C. panels, 364

regulators, see Regulators.
Voltmeter switches, 8, 11
Voltmeters, see Instruments.

Walker isolated plant switchboard,

326

Watt-hour meter, see Instruments.
Wattless component indicator, see

Instruments.

Wattmeters, see Instruments.
Welding capacities, 316
panels, 315
processes, 316
Westinghouse carbon breakers, 66-

control switch, 14
instruments, 179-191
oil circuit breakers, 124-156
brush contacts

type B, 130-134
C, 139-141
CO, 145-147
E, 134-139

0, 141-145
Butt contacts

type G, 147-156

H, 129

knife contacts
type D, 124

1, 124

multiple-multipole, 127
wedge contacts

type F, 126
regulators, 245-253
Weston instruments, 192-197
Wire and cable, 402
Wooden switchboard, 276

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