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Morey, C. R. |[
Lighting arresters and ^r
schemes foor testing fv;~
For Us3 In L::>r2ry Only
SCHEMES FOR TESTING
O. R. M(^RP:Y and T. C. OEHNE, Jr.
PRESIDENT AND FACULTY
ARMOUR INSTITUTE OF TECHNOLOGY
FOR THE DEGREE OF
BACHELOR OF SCIENCE IN ELECTRICAL ENGINEERING
HAVING COMPLETED THE PRESCRIBED COURSE OF STUDY IN
ELECTRICAL ENGINEERING i,|N(limN , im r-m.
■LLiNUIblNohiUlt Or TECHNOLOGY
PAULi/ GAL VIN LIBRARY
' ' ~^ 35WEST33ROSTRgF-
■''-'""AGO i( f^nsip
TABLE OP CO\TXE¥TS.
PART I. Page 1
PART II. Page 8
Description of Types of Lightning Arresters.
PART III. Page 25
Description of Tests Proposed and Used.
PART rv. Page 36
Performance of Proposed Tests,
PART V. , Page J.
PART VI. Page
INTRO DUCTI0 1<1.
During thunder-storms slectrlc wires
iDScoine charged from the atmosphere with an
slectric potential, different from that of the
earth; there is then a tendency to establish
an equilibrium, --that is, for a discharge to
or from the earth as the case may be. The ten-
dency for a discharge to take place is not al-
ways due to lightning but is often due to ef-
fects similar to those caused by lightning a-
rising from entirely different sources, as
sv;itching, etc. If the discharge be left to
choose its own path it will select one or more
of the weaker points, usually the most vital
part of the system, and thus rupture the in-
sulation. It therefore "becoraes necessary to
rid the line of this charge in some suitable
manner, and without allowing it to damage any-
port ion of the system.
The most difficult charge to take
care of is the direct stroke, A direct stroke
frequently splinters poles, so violent is the
discharge to earth. The commoner charge met
with is one induced from a charged cloud, and
when the cloud discharges to earth, a free
charge exists on the line, which immediately
begins to travel in "both directions v.-ith a ve-
locity almost equal to that of light. Either
of these forms of charges may expend their pow-
er in traveling if they run a sufficient dis-
tance "before encountering an obstruction.
There may be a slow accumula,tion of charge due
to rain, snow, or fog drifting across the line
which will show itself as a series of small im-
pulses. Charges may be accumulated from slip-
ping "belts, etc. A surge may be started by a
sudden change of load or connecting or discon-
necting apparatus from ths line.
When a wave of high potential travels
to a generator, motor, transformer, or any
piece of apparatus having a coil, a choking
effect is experienced by the wave. It seem-
ingly meets something having inertia, and as
it rebounds and packs up the potential rises
suddenly, and frequently a discharge results
rupturing the insulation. This choking ef-
fect is in all probability due to the highly
oscillatory character of the surge. It is due
to this fact that when a discharge seeks a path
to earth through the coils of a dynamo, motor,
or other apparatus, it punctures the insulation
of the same, and takes the path to earth of
least impedance, which is generally through
the ?;ir-ding of an anuaturft to the core.
In order to remove this rise of po-
tential from the apparatus, a choke coil con-
sisting of a few turns of wire is placed "be-
tween the line and the apparatus to 'oe protect-
ed. Now tha arrester is placed where the elec-
tromotive force is apt to raise the highest, --
that is, on the line side of the choke coil.
The statement has "been made and seems
to have been "borne out in practice, that dis-
ruptive dischargee form nodes. Therefore a
lightning arrester cannot be said to protect
any given distance as it may be at an anode
and the discharge pass it completely. The
choke coil tends to form a node, but at times
it has been found advisable to use a number of
coils and lightning arresters on the same line
in a station.
In 1844, v!h.en Morse established his
first telegraph line, some means had to he de-
vised to take care of the charge en the line.
This v/as accomplished hy means of a lightning
arrester. A lightning arrester pure and sim-
ple is nothing more than a convenient part or
outlet from the charged "body to a point of low-
er or no potential. The arrester used hy iaorse
which in its fundamental principle has been
used ever since, v^as a spari gap through the
air. When electric lighting was introduced
the problem of protection became more compli-
cated, due to the dynaiao short-circuit that
invariably follows the discharge. Devices to
interrupt the short-circuit and restore the ar-
rester to normal condition had to be used. An
ideal arrester for all purposes v/ould be one
having a simple discharge gap of such a char-
acter as not to penuit a short-circuit, or,
"better yet, metallic ccrinections to ground
The reason for using an air gap in
preference to that of substituting some form
of resistance, is that it is of variable re-
sistance, depending upon the conditions.
Ordinarily it is a good insulator, but to a
discharge it offers far less impedance than an
artificial resistance of much less resistance.
The second reason is that it can instantly be
restored to normal. It absolutely prohibits
the flow of the normal current unless it is
broken down, under which conditions its re-
sistance reduces to a minimum.
The improvements in lightning ar-
resters in the last fevi' years has been in the
way of circuit-interrupting or arc-prohibiting
features whicli have 118001116 necessary on account
of the different currents employed. The suc-
cess or failure of an arrester can be attribut-
ed mainly to its successful performance of the
duties devolving upon these additional features,
DESCRI'PTIO^T OP .DIPPEKRT7T TYPES OP
The first lightning arrester devel-
opment was along the line of telegraph protec-
tion. These arresters, due to the lov/ line
voltage, were extremely simple, consisting in
general of simply an air gap hetwesn one line
and the ground. A very sijiall air gap hetween
copper or "brass electrodes sufficed to prevent
the low voltage line current from following
the discharge. Various tjrpes of relays were
used for grounding the circuit automatically,
which required resetting after the disturbance
In power circuits the proposition
was very different. The line voltage was suf-
ficiently great to hreak across a simple air
gap after it had passed a spark. Many devices
were designed to overcome this difficulty. One
of the most noteworthy types of early lightning
arresters for power lines is one designed by
Professor Thompson and described in the Elec-
trical World for 1886. This consists primari-
ly of a gap "between horn shaped electrodes.
The air breaks down across the narrowest or
lowest part of the horns and, due to the heat-
ed air rising, there is a tendency for the arc
to he carried upvra.rd to the v/ide portion of
the gap. This much of the device had been used
previously in Europe. To this, however, Pro-
fessor Thompson added the magnetic field. He
so placed a solenoid that its field enveloped
the gap. The reaction between the air and the
field also tends to raise the arc to the wider
portion of the gap. This arrester is clearly
ahovm in Pig. 1. When applied to direct cur-
rent series arc lighting systems the gap was
placed between the line and the ground, v^hile
the solenoid was placed directly in series
with the line. The connections are clearly
shown in the figure. "li" is the machine ter-
minal, "L" connection to the line, and "E"
connection to the earth. For series arc
lighting systems the arrangement was found
quite satisfactory, the current remaining con-
stant at ahout six or seven amperes and fur-
nishing a constant fVjcK in the gap. For in-
candescent lighting, however, the current
varies greatly and could not always oe depend-
ed upon for hlov/ing the arc. This necessitat-
ed the solenoid oeing in the ground circuit,
that is, in series with the gap. In this
latter case it is evident hoth resistance and
inductance have been introduced into the ground
circuit, which is very undesirable. The re-
quirements demanded by direct current series
arc lighting systems not oeing particularly
rigid, this lightning arrester has answered
fairly well and it is in many of these instal-
The "Central" lightning arrester,
which came out a short time after the Thompson,
represents another class in which the air gap
is increased by a mechanism electrically con-
trolled. This arrester is illustrated in Tig,
2. The discharge passes through the solenoid,
across the gap "C" , along the arm "D" , when it
crosses to the revolving arm and thence to
ground, A dynamic current which holds across
the gap "C" energizes the solenoid and moves
the armature. This motion increases the gap
at "C" and loosens the revolving arm, and an
arc is drawn out across the gap produced hy
the motion of the revolving arm. The gap at
"D" is of such size as to prevent the arc be-
ing maintained. The rotation of the arm is
accomplished "by winding a string, suspending
a weight, upon a drui'i attached to the arm .
In this arrester the circuit to ground contains
a coil. This is a had feature, arcing is quite
apt to occur across this coil. Another ohjec-
tion to this arrester is the fact that it does
not furnish a continuous path to earth hut one
which may he hroken for much of the time.
The Fulmen lightning arrester repre-
sents one of the more successful designs of the
fuse type arrester. This arrester came out
about 1892. A fuse was placed in the circuit
from the line to the ground. In order to keep
the arrester in service after one fuse had
blown it was necessary to automatically cut in
another. Ten fuses were arranged in parallel
with each end projecting into a channel. A
carbon block in each channel made contact with
the end of one fuse and the ground or live
wire. As the first fuse "blew the blocks slipped
in the channel due to gravity until caught by
the projecting ends of the next fuse. As each
fuse blows its endsare fused and the blocks
slide down to the next. It is quite evident
that this arrester was serviceable for only a
limited nujuber of discharges.
An interesting type of lightning ar-
rester which came out about 1890 was known as
the "Razzle -Dazzle." A metallic ball was sus-
pended above a grounded plate. A discharge
jumped the gap but the ball, being free to
swing, was set in motion by a dynamic arc.
Any motion of the ball increased the gap thus
drawing out the arc. From such information as
is availalole it is not believed that this ar-
rester was ever very popular,
Alexander J. ¥urts has had a great
deal to do with the development of the light-
ning arrester. One of his early types \ms the
¥insor-¥urts lightning arrester. In this ar-
rester the path to ground was first across a
gap bridged by a carbon ball, then across a
gap between carbon electrodes to ground. The
second gap is contained in a chamber. In the
neck which rises above this chamber is the
first gap. A dynamic arc has an explosive ef-
fect and the air raises the ball, thus placing
another gap in circuit. If the arc should
make across this gap also, the draft of air is
calculated to blow it out. This arrester
v/orked quite Satisfactorily on 1000 volts di-
rect current but was not a success on 500 volts.
A 500 volt arrester was larought out on the mar-
ket composed of two chambers. The gap was be-
tween carbon electrodes, one of which entered
through the top. A dynamic arc blows this
electrode out of the chainber and it revolves
through 180 degress and drops into a similar
chamber and is ready for another discharge.
This arrester vas designed for 500 volt street
rail7/ay service and was manufactured by the
¥estinghouse Company. In his experiments Wurts
discovered that when brass electrodes were
used on alternating current some compositions
of brass acted differently from others. Upon
investigation he found that brass containing
much zinc was the best. He explained it in
this manner: Zinc and antimony supply the arc
stream with oxide of metal, which chokes the
arc with vapors of high resistance. Other
metals, such as copper, aluminum, Toronze, etc.,
furnish the arc stream with pure vapors of the
metal itself, r.hich offer comparatively no re-
sistance to the passage of a current. Cadus-
ium, hismuth, magnesium, and mercury were found
to have this non-arcing property. The vapors
of these metals are also unidirectional, — that
is, they have a tendency to prevent a reverse
of current. The non-arcing property is also
very largely due to this. The arrester con-
structed of non-arcing metal "best suited the
alternating current and the gaps must be small--
1/32 or 1/64 of an inch, in order to hold the
vapor hetv/een electrodes. In the type of ar-
rester v.hich involves this principle the gap
is made between metal cylinders which have
knurled surfaces. In a 1000 volt arrester
seven cylinders are used, numbers one and
seven are connected to tlie lines and the piid-
dle cylinder is connected to the ground, inaJc-
ing three gaps from line to ground and six gaps
hetween lines. Another arrester hrought out
by ¥urts for street railway service was inade
hy inclosing two copper electrodes between
lignum vitae blocks. A number of paths burned
into the blocks served to conduct the spark be-
tween electrodes. Due to lack of oxygen vapors
of the electrodes are not apt to form.
The Garton-.Daniels lightning arrester
is very widely used on both alternating current
and direct current circuits. The path to earth
is across a number of gaps, through a carbon
rod of low resistance. Through a flexible con-
nection it passes to a plunger in a solenoid
and across a gap to ground. The solenoid is
shunted across one or more gaps and the resist-
ance bar. A static discharge avoids the solen-
oid due to its inductance, Tout the dynamic cur-
rent follows the path of least ohtnic resistance
which is through the turns of the solenoid.
The solenoid "being thus energized raises the
plunger, introducing another gap in series with
"both the static and the dynamic path. The arc
across this gap is made in a cylinder which
prevents violent burning due to a lack of oxy-
gen. This arrester is largely used on the feed-
ers of electric railways.
The Wirt non-arcing lightning arrest-
er described in the Electrical World in 1897
has been used quite extensively. This arrester
in the path, to ground has a resistance and an
air gap between large metal cylinders. The
grounded cylinder is the center one and serves
for both sides of the line. The non-arcing
property is due to the cooling effect of the
metal cylinders. In order that the arc shall
not hecome too hot a carton resistance is
placed in the circuit to limit the flow of
current. This arrester will break an arc on
2400 volts alternating current "but v.'ill "burn
up on 500 Tolts direct current. A reversal
of the current is necessary.
The Universal Non-Arcing lightning
Arrester, also ]cno?m as the Shaw Lightning
Arrester, is made up of a series of discs of
non-arcing composition separated from each
other by sheets of mica. A static discharge
passes through the thin sheets of mica in very
minute sparks which do not have sufficient body
to pull an arc. The combined resistance of
these mica sheets is much less than that of a
simple aggregate thickness. For a time this
arrester was ver^- popular. Its chief objec-
tion is Its large depreciation.
One of the most recent and extensive-
ly used lightning arresters is the multi-gap
arrester. It consists of a number of series
gaps betv/een cylinders of non-arcing metal.
Some of these gaps are shunted with a non-in-
ductive resistance. The most recent designs
have a number of resistance rods, each of which
shunts a different niimber of series gaps. These
resistances must be of different values, the
greater resistance shunting the most gaps. The
path which is chosen by the discharge depends
upon the frequency. The ¥estinghouse Company
also advocates the use of a series resistance
which is placed between the series gaps and
the ground. The function of the series and
shunt resistances is described by Percy H, Thomas.
The series gaps ars set so that they do not
"break dov/n under line potential. An electro-
motive force which will treak across the ser-
ies gaps will also treak through the shunt re-
sistance. As the alDnonnal electro-motive force
is reduced the shunt resistance takes so much
current that the arc goes out over the shunted
gaps but holds over a few gaps and through two
resistances, series and shunt. These resist-
ances are of such a value that the current is
too limited to hold over the gaps in series
and thus the arc is extinguished. The lighter
discharges are taken care of by the resistances.
A discharge path containing considerable re-
sistance can be set to discbarge v;ith a very
slight rise in voltage. These arresters are
made in panels for high voltage station work.
The most promising type of lightning
arrester is the Electrolytic Arrester. HWien
aluminum is placed in certain electrolytes
and a current passes it has the property of
coating itself with a non-conducting film.
This film forms for the impressed voltage "but
will "break down in myriads of tiny punctures
if the voltage is raised; that is, it has
nearly infinite resistance for the impressed
voltage and zero resistance for any voltage
ahove . A sufficient number of these cells
combined will act admirably as a lightning
arrester. The cell has a slight leakage cur-
rent and will take a charging current with an
alternating electro-motive force. To prevent
the cell from taking current continuously a
gap is put in series. The film, however, de-
teriorates hence making it necessary to con-
nect the cell in circuit at intervals of tv/o
or three days. Although this s-rrester has "been
on the market only a very short time, it seems
to have given general satisfaction.
A lightning arrester used to a large
extent in Europe and one which has given very
good satisfaction is that known as the Perman-
ent-Leak Lightning Arrester. The make up of
this arrester is shown in Pig. 3. It consists
of two horizontal water pipes, flow and return
efficiently connected with the neutral of the
generator and the station earth plate. These
are vertical pipes of glass connected to the
flow and return pipes. These vertical tubes
are joined at the top hy pieces of glass tuh-
ing in the form of an inverted "V" having a
glass "bulb in the center, into which the point
of the line wire dips, being made water-tight
by a plug of India-rubber. The maximura resist-
ance for one line through the pipes is about
700,000 ohms making the laakage very sifjall.
Other protective devices are used,
such as grounded wires suspended near the line
wires and lightning rods on the poles. In gen-
eral it may he said that lightning arresters
have protected apparatus and lines from serious
damage due to disturhances of the most frequent
DESORIPTIOF OF TESTS
USED OR PROPOSED.
It is very difficult to judge of the
success of a lightning arrester due to the many
conditions upon which the successful operation
depends. One of the most important conditions
is a straight connection to the line and ground,
and a good ground. Up to the present time the
only satisfactory method of determining the
value of an arrester is service. Laboratory
tests at hest only offer a means of comparison.
In the laboratory it is impossible to reproduce
conditions met with in practice. It is not ex-
pected that an arrester will be of service in
a direct stroke. In such cases a discharge
usually occurs before any obstruction is met
with and the arrester at best can only ward off
a dangerous uss at some distant point.
There have been a number of tests
devised for obtaining some idea as to how a
liglitning arrester vroutld operate ?;hen actually
installed on a line. These tests have more or
less come down to be comparatiTe tests. One
of the earliest comparative tests that met with
any success vvas that devised hy Er. Tagarde in
1857. A diagram of his test is sho^A-n in ?ig. 4.
He obtained his electricity from a 0,03 micro-
farad Leyden jar charged by a ¥imshurst static
machine. The Wimshurst machdne used was oper-
ated at 1200 revolutions per minute, at v;hich
speed it gave a spark from 0.15 to 0,20 meters
in length. The spark on discharge through the
apparatus was from 5 to 6 centimeters long.
In setting pp his apparatus he avoided crossing
any of his wires. The v/ires were placed at
least 50 centimeters apart on account of the
great difference in potential. He deemed this
large distance necessary inasmuch as during
his first test rrdth ths wires only 10 centi-
meters apart a crackling of discharge passing
through the pores of the insulation v/as ob-
tained. All the wires used were insulated ■by-
three layers of gutta-percha.
In Pig. 4 the terminals of the
charged Leyden jar are connected to points 1
and 2. These tv^fo points are insulated from
each other, as shoiNTi, by means of a plate of
gutta-percha, C and C* are fuses put in to
protect the apparatus. D and D' are 500 ohm
hells. The circuits A B C D K and A B» C D' K
are identical. E and E' are "indicators" con-
sisting of a plate towards which a platinised
screvr can be brought up. The test is conducted
in the following manner: The charge divides, a
part passing through the lightning arresters B
and B' and the rest through the bells D and K',
and the "indicators" E and E» . E and E» are
cali"brated by means of a battery. The pitch
of the screvr "being knovm. The number of turns
of the screw being counted, thus giving the
amount of charge over D and D' in comparison
?;ith that over B and B'. In making use of
this test M. Lagarde put a lightning arrester
at B whose performance had been studied v/hile
actually installed on a line, and at B' he
placed the arrester which he wished to study.
This is one of the most successful tests for
the comparison of tv/o arresters and the results
obtained by M. Lagarde were iDOst satisfactory--.
In 1890 Alexander J. Wurts performed
a large number of experiments on lightning ar-
resters. In his first experiment he placed a
saw tooth carbon arrester across the line of a
1000 volt alternator. He used about 150 yards
of line wire. In the circuit he placed a
switch by means of which he cut the arrester
in and out of the circu.it. Just in frort of
the alternator, across the line, he placed a
short circuiting device 7/hich vi/as set to oper-
ate at large currents, thus protecting the al-
ternator. He bridged the air gap of the arrest-
er with tin foil so as to start an arc. The
first trial was very satisfactory, but after
that the carbons of the arrester were heated
to a white heat and the generator pressure re-
established an arc across the hot air gap. The
carbon did not conduct the heat away fast e-
nough. In his second attempt he substituted
solid round brass rods in place of the carbon
saw tooth arrester. He kept the short circuit-
ing device in circuit and the results were very
good. In his third trial he omitted the short
circuiting device and used a 3C00 light alter-
nator. He o^btained a small arc and in all oth-
er respects the test we.s very good.
Twice the protection afforded in any
case is directly proportional to the difference
in resistance to static discharges offered hy
the lightning arrester from that offered by the
apparatus it is intended to shield; preference
should be given to devices that have the lov.'est
equivalent spark gap, which should always he
considerably lower than that of the apparatus
to be protected. By equivalent spark gap is
meant that definite form of gap which, when
placed in jnultiple v;ith the arrester, just
fails to take the discharge. The length of
this gap is the measure of the freedom of dis-
charge of an arrester.
Fig, 5 indicates a suitable method
of measuring this equivalent spark gap given
"by Ikr. R. P, Jackson. He makes uss of a high
tension transfonner in series v/ith the second-
ary of vvhich is placed a sv/ing switch, a series
gap, and the lightning arrester virhose equiva-
lent spark gap we wish to ootain. In multiple
with the arrester is placed the measuring gap.
Across the line is connected a condenser. The
object of the condenser is to give volume to
the spark. The little gap in series with the
swing switch "breaks down when the switch is
closed and adds to the suddenness of the v/ave
striking the arrester.
In 1907, ir. Percy H. Thomas devised
some tests for lightning arresters to he sub-
mitted to the Standardization Committee of the
American Institute of Electrical Engineers for
adoption in the standarization rules. He con-
sidered that the purpose of the standardization
rules should he to give such directions and in-
formation for the comparison and test of light-
ning arresters as may be likely to he of gener-
al pratical use, and v/hich are of such a char-
acter as to he generally agreed to and accepted
hy engineers having experience with the use or
design of lightning arresters. T7ith this in
view Mr. Thomas proposed the following tests:
The first test is the actual measure-
ment of the hreak-down voltage of an arrester.
This is best done at normal frequency. The
needle point spark gap is employed in this test.
The spark gap is placed in multiple with the
arrester and the gap opened until it just neg-
lects to take the spark. The distance betv;een
the needle points is measured and the break-
down voltage obtained from the calibration curve
of the spark gap.
The second test proposed is the de-
termination of the protective power of the ar-
rester which depends upon the maximum impedance
offered to the discliarge. This can he nothing
more than a coinparative tast due to the influ-
ence which the characteristics of t'-^e circuit
and apparatus to "be protected has upon this
quantity. It is measured by subjecting the
arrester to a high-frequency discharge frcan a
condenser, and obtaining its static equivalent
by the equivalent needle-gap method. Either
of the circuits shovm in Figs. 6 or 7 may be
used for this test, depending upon the apparat-
us at hand.
The next test proposed is the deter-
mination of the power to suppress the generat-
or arc. The test is made by reproducing oper-
ating conditions; that is, connecting an ar-
rester across a powerful supply circuit and
passing a static discharge across the whole or
part of the arrester to initiate the generator
arc. The circuit for this test is shovm in
Pig. 8. Any arrester, to he of commercial use,
should he aole to suppress the generator arc.
The capacity for frequent discharges
is determined by the same method as the last
test. The kind of arrester used has a great
deal to do v/ith this property. High-voltage
arresters v;ill presumably discharge much less
frequently than will low-voltage arresters, as
in the former minor disturbances will not be
able to pass to the ground. Furthermore, on
alternating-current circuits at least, dis-
charges occurring at one part of a cycle are
more severe than discharges occurring at anoth-
er, which tends to relieve the arrester.
In making this test a nviaber of discharges
should he produced in succession at inter-
vals of some seconds, the exact number of
repetitions and the intervals being deter-
mined according to the circumstances of the
There have been a number of other
tests proposed by different men well up on
the subject of lightning arresters, but those
already mentioned cover fairly v;ell the points
to be considered by a person in purchasing
PERPORMAUCE Or PROPOSED TESTS.
As previously stated, too much must
not te expected of a lalDoratory test. Many
schemes for testing laaTS been proposed from
time to time--3ome employ a static machine,
while others use a high potential transforra-
er. An author, in writing of his methods
for testing, is apt to over-estimate their
importance. Since most of the literature
on lightning arrester testing is "by some one
advocating a particular test, the engineer
who has had no experience in this work receives
the impression that the results ootained are
final and of primary importance.
All the tests tried were with the
use of a high potential transformer. Many
proposed schemss were tried and the results
obtained from some will be given. The method
of measuring the voltage at which a spark oc-
cuf"red gave some difficulty. Electrostatic
voltmeters were tried, but, due to the ranges
of the instruments available, they were not
satisfactory. A spark gap between needle
points is the standard method for measuring
high voltages. In this case the gap is in
parallel with the arrester, and set so that
it divides the discharge or just fails to take
the discharge. Whan the arrester discharge for
minimum voltage is measured in this v/ay, the
distance between the needle points of the spark
gap is called the equivalent spark gap and is
a measure of the arrester's impedance. Care
must be taken that the readings are taken with
sharp needles. The points frequently burn and
a preliminary setting should "be made v;ith nee-
dles which have "been slightly turned. The
final setting and distance measured is that te-
tv/een new points. In all tests nujnber 1 and 2
sewing machine needles were used. The stand-
ard calibration for a needle gap as given hy
the standardization rules of the American In-
stitute of Electrical Engineers is for mean
effective pressures assvucing a sine wave. It
is, however, the maximum voltage which hreaks
down the gap and the wave form Lvust therefore
Another method used v;as to step down
the voltage with a transformer whose ratio of
transformation is absolutely known. Thus a
reading could he obtained on a low potential
voltmeter. For a potential transformer a Lakon
and a General Electric transformer were checked
and found to be very accurate within the lim-
its for which they v;ere to "be used. The volt-
meter method was the one which seemed to give
the most consistent results. Some of the mod-
ified forms of spark gaps, such as a gap "be-
tween spheres or needles provided with shields,
might he advisal'le, but were not tried.
Among the first schemes tried v/ere
those proposed by Mr. Percy H. Thonias and pre-
sented before the American Institute of Elec-
trical Engineers at 'JTiagara Palls ir June 1907.
The scheme shown ir; Pig. 6, which was also pro-
posed by Ivir. Creighton some time previous, was
tried, using instead of the static machine a
high potential transformer. A sv:itch vra,s put
on the low tension side of the transformer.
The voltage could not be satisfactorily meas-
ured with a needle gap. The needle points were
fused at almost every discliarge. In series
with the gap a high ohjnic resistance Vv-as placed
to limit the current. This was only partially
successful. Tha quality of the discharge was
much poorer. Aftar the employment of a swing
switch and more capacity in the condensers than
were in the condensers of the Leyden jar tuoe,
this medthod was abandoned without having ob-
tained any satisfactory data. In an effort
to open the circuit more rapidly after obtain-
ing a discharge, a very delicately adjusted
relay was placed in the primary circu't. which
in turn operated a circuit "breaker, thus open-
ing the circuit. The device as a protection
to the apparatus v/as quite a success as far as
the opening of the circuit was concerned. It
failed, however, to operate until after the
needle points had "been fused. In the tests
su-Dsequeritly tried tliis device was introduced
as an emergency protection, inasmuch as it
could "be used vdtliout interfering in any way
with the operation of the test.
The next test tried was that shown
in rig. 7. The discharge gap ?7as made he-
tween spheres of ahout one-half inch in diam-
eter. Condensers of various capacities were
also tried. Leyden jars proved the most suc-
cessful. A plate condenser in v/hich the di-
electric was oiled linen and paraffine paper
gave considerable trouhle and was finally dis-
carded. \"hen placed in circuit on three or
four thousand volts the temperature of the con-
denser rose until a "break dov/n occurred.
The location of the swing switch was
changed after considerahle experimenting, and
was finally placed on the high tension side.
It v/a6 njade in the form of a pendulimi, about
tv/o and one-half feet long, provided with a
sliding weight to change the period. Contact
was made with the light flexible piece of brass
for a very short length of time. It was found
advisable to place the condensers between the
swing switch and the transfonnerr, as the charg-
ing current does not then pass through the
switch. The objection to passing the charging
current through the switch is that the switch
draws out a considerable arc and the suddenness
of the discharge was spoiled. With this ar-
rangement a constant voltage was maintained on
the secondary side and a step down transformer
and low potential voltmeter was used to measure
the voltage. TTith the scheme as described
above, a supply spark was obtained over both
the arrester and the needle gap. The data
cttained with the spark gap could not te re-
produced. J"ust to what this was due* could not
be determir-ed. The setting of the series dis-
cliarge gap prohably has some influence. The Yolt-
meter readings, however, were reproduced quite
satisfactorily in most cases. This led to the
adoption of the voltmeter as the standard, and
frequent attempts were made to check with the
spark gap. "While data ?ra,s obtained with this
scheme, it was not considered satisfactory and
other schemes were tried.
The scheme of Ivjr. R. P. Jackson, in
the Electric Club Journal of ]«arch 1908, is
quite similar to the one just described. The
scheme of Jackson is shown in Jig. 5. The
saDie swing switch, series discharge gap and
condensers were used as in the previous schemes.
The condenser was made up of twelve Leyden jars,
quart size, plaxed in parallel. As an experi-
ment, the condenser was placad in parallel with
the arrester and needle or measuring gap. The
series or discharge gap is now hetv/een the con-
denser and the swing switch. This increases
the arc at the switch, "but placing the series
gap "betv/een the condenser and the switch gives
this arc more the form of a hee-vy static dis-
charge. A snappy spark was produced at the
arrester. Very little difficulty was experi-
enced v;ith the needle points. It was clearly
demonstrated that the series gap effects the
discharge. For this reason the setting of
this gap was changed frequently to olitain the
hest position. Using the arrangement shovm in
Tig. 5, except for the change in location of
the condenser as described, the following re-
sults were obtained: The first arrester tested
for equivalent spark gap ta^s a V'urts non-arc-
ing lightning arrester. The lowest voltage at
which a spark jumped the series of gaps from
line terminal to line terminal was 3250 volts
mean effective, or a maximum of ahout 5500,
The arrester is designed for a line voltage
of 1000 volts. This necessary rise is rather
high. The condition of the insulation of the
apparatus to he potential miust "be very good
indeed to benefit much from the presence of
the greater. It should he stated here that
the arrester has never heen in service hut is
far from new and not of recent design. This
hreak down voltage vms measured hy the volt-
meter method. The results obtained with the
use of the needle gap will be taken up later.
The voltage at which the condensers are charged
and that impressed upon the arrester depends
upon the points of the wave at whicS? the swing
switch niakes contact. The switch may make con-
tact on any point of the wave. Therefore, in
order to ohtain the conditions looked for, name-
ly, contact at maximum voltage, the switch is
kept in motion and considera'ole time allowed,
to make sure that contact must have heen made
on the peak of the wave at least cnce. Tor
this reason there is an argUinent in favor of
the synchronous switch which shall always make
contact on the peak of the wave. A device of
this kind in the form of the contact -maker
should not he difficult to construct and its
use is advised. It is quite evident that if
the swing switch did not make on the peak of
the electro-motive force wave, the reading
octained hy the voltmeter is not correct.
There is then this chance for error in the
matliod esiployed. Tlis form factor for the
electro-motive force wave of the alternator
used is 1.74, being a very peaked wave, With
but very little load on the secondary side,
this form factor will hold quite well for the
Tftuve form on the secondarj'- side. Thus it vra-s
assumed that the v/ave form remain practically
unchanged. An oscillograph should be used to
determine this definitely.
In testing the art breaicing power
of the arrester an effective pressure of 1000
volts was impressed across the line terminals.
An arc must be started by a discharge. It is
evident that if a discharge is to pass clear
across the series of gaps the terminals of the
discharge circuit cannot also tap onto the line
terminals, as the discharge v/ill pass back
through the line and transformer or alternator
supplying it. This was found to Tdb true in
spit 8 of the inductance in this circuit. In
this particular arrester ths scheme can "b.e
satisfactorily employed hy placing the dis-
charge terminals so that there are as rnany
gaps or nearly as many in the circuit back
through the transformer as across the remain-
ing space between the discharge terminals.
In this case they were made equal and the dis-
charge voltage raised until the sparlc passed
both v;ays , completely bridging all gaps between
line terminals. The arc was satisfactorily
bloTATi for all voltages tried wliich were as high
as 1300 volts. This test cannot be relied upon
as final as the alternator used to supply the
imaginary line was of limited capacity and it
is believed that the generator capacity must
be considered. As regards frequency, 60 cycles
were used for Tooth alternators. The discharge
frequency, however, "being that from a condens-
er, can only he estimated.
After comparing data taken at vari-
ous frequencies, it is helieved that frequen-
cies "between 25 and 100 cycles have practically
the saane effect. The slight variation which
was shown in the data did not seem to hear any
definite relation to frequency and so must have
heen due to other causes.
In the tests of the Wirt arrester,
the lowest "break down voltage was 2950 volts.
These tests were made at 60 cycles and the
voltage was measured "by the voltmeter measure.
This arrester was designed for a 2000 volt
line and is one which has seen con3idera"ble
service, and "before making the tests it was
not thoroughly cleaned, only loose dirt "being
removed. This arrester, therefore, represents
more nearly the conditions apt to loe met with
in service. Por the test to determine the ar-
rester's ahility to hreak the arc, the same
method as used on the ^'urts' arrester was em-
ployed. There being five cylinders in series
between the lines, tvro gaps could he put be-
tween the discharge terminals, leaving two in
the circuit through the line and transf or;uer.
As in the case previously described, the spark
was forced to divide, thus bridging all the
gaps betv/een the lines. A line potentie.1 of
2500 volts failed to produce an arc following
a discharge, so the limiting device, while not
considered perfect, compared favorably with
other arresters tested.
The next type tested was a Gifford
3000 volt arrester. The gaps here are in
parallel and adjustable. "tTo change whatever
was made in the setting of the gaps, they hav-
ing been set by the manufad:iirer. The break
down voltage at 60 cycles was 2500 volts mean
effective, or a maximum of approximately 3900
volts. "Sow for a sine wave the mean effective
pressure corresponding to this maximum falls
below 3000 volts, the line voltage for which
this arrester is intended. Seemingly this in-
dicates that the arrester would be apt to dis-
charge on line voltage. A 3000 volt line,
however, was placed across it without a dis-
charge. The data being for an impulse, it
appears that in practice the arrester would be
apt to discharge very frequently, not neces-
sarily due to any use in potential but simply
the normal electro-motive force suddenly ap-
plied. To test the arc-disrupting ability of
this arrester, the methods previously described
did not apply, so it oecame necessary to oridge
the gap with tin foil, thus producing an arc.
The method in this instance was very unsatis-
factory, due to the limited current that could
he obtained at this voltage. Again this
demonstrated the limitations of laboratory
tests which are usually met with. This arrest-
er is set very low, and unless it has unusual
capacity is apt to injury from heavy currents
and frequent discharges. There is danger in
trying to male? an arrester too sensitive. As
previously mentioned, the gaps are adjustable
and this low break dovm voltage may be varied
by slightly increasing the gap. In an arrest-
er of this type it is impossible to uiake the
paths of equal impedance and so some break dovm
long before others. From watching operations
of this arrester, it must "oe said that the
quantity conducted to earth across each gap
is small. The spark is very fine and noseless.
A paper placed in the gap shows a clean small
hole without any burning. An important test
of an arrester of this kind and the V7irt type
is one, of the carrying capacity of the carbon
rods and their consistency as regards resist-
ance. This test was not made but is advised.
With this incomplete set of data the
engiaeer has a key to the characteristics of
the various types tested and a certain amount
of comparison is possible, "NTow to take up the
measurements of these voltages with a needle
gap. As an example, the Wurts non-arcing ar-
rester discharged at 3250 volts mean effective
according to the voltmeter method of determina-
tion, while with the spark gap the mean effect-
ive was aloout 10,000 volti^ TDased on a. sine wave.
The v/ave of the alternator used varied decided-
ly from a sine v/ave . Therefore in this case
the calibration in mean effective pressures, as
given in the standardization rules of the Amer-
ican Institute of Electrical Engineers, will
not hold. However, hy using the form factor of
a sine ?;ave these mean effective values may he
replaced hy maximijim values and the actual mean
effective for the Vz-ave used deducted from these.
Employing this method, however, accounts for
only a small part of the discrepancy. Some of
the error it is safe to assvime is due to the
contact not having "been made at the maximum
point of the v/ave . This explains why the spark
gap was not depended upon as a measuring device.
While the actual data recorded is not
of any particular importance, the testing of
numerous proposed schemes gave considera-ble in-
forme^tion. Many tests which have "been proposed
are not practical, and even in the "best there
are f lav.-s . Originally it was intended that af-
ter finding a suitable scheme for testing, com-
mercial tests v;ould be made on a nuinber of ar-
resters. That these tests could not be made
was due to lack of time. In connection with
each scheme tried, considerable experimenting
was required to determine if it could be laade
practicable. The time and work put in in this
way does not show in the report, as no numerical
data was obtained on those that failed. Con-
denser and transf or.ner troubles in the form of
burn-outs consumed considerable time. The tests
given were obtained with the scheme last developed
It is believed that this is a practical scheme
and can be used to advantage for a comparison of
American Lightning Arresters.
American Electrician, ITovember, 1898.
Atmospheric Electricity and Lightning Protectors.
Engineering, May 30, 1902.
Benefit of Enquiry in Lightning Arrester Practice,
Electrical Review, IJew York, September 8, 1906.
Choke Coil Protection.
Electric Club Journal, March, 1906,
Correct Position of Lightning Arresters in the
Circuit and the effect of Choke Coils.
Electrical Engineer, London, June 25, 1905.
Developments and Experiments with Lightning
Electric Club Journal, January, 1905.
Discovery of Non-Arcing Metals.
Proc. Am. Inst. Elec. Eng. March, 1892.
Discriminating Lightning Arresters and Recent
Progress in Means for Protection Against
Proc. Am. Inst. Elec. Eng. May, 1894.
Equivalent Spark Gap.
Electric Club Journal, April, 1905.
..■■I ,.' is
.-9 '7: .dx-.I
Experiences with lightning Protective Apparatus.
Proc. Am. Inst. Elec. Eng. October, 1905.
Foreign Lightning Arrester Practice.
Electric Cluh Journal, JDecemTaer, 1905.
Functions of a Lightning Arrester.
Electrical Review, Nev/ York, May 11, 1898.
Function of Shunt and Series Resistance in
Electrical World, June 21, 1902.
High Tension Lightning Protection.
Electric Railway Review, October, 1906.
Installation of Lightning Arresters,
Electrical World, September 24, 1898.
Investigation of Operation of Lightning Arresters
Electric Club Journal, iJarch, 1905,
Lightning and Lightning Arresters.
Electrical World, June 11, 1898, June 25, 1898.
Lightning Arrester Diagrams,
Electrical World, June 10, 1905.
Electrical Review, "tTew York, February 26, 1896.
August 19, 1896.
Electrical ¥orld, June 1, 1901.
Lightning Arresters and Photographic Study of
Electrical ^orld, January 1^, 1889,
Teoruary 23, 1889.
Lightning Arresters on Transmission Lines.
Electrical Revisv;, ¥ev; York, October 10, 1903.
Central Station, April, 1906.
Electrician, Hew York, March 9, 1904.
Electrical World, June 17, 1905.
Lightning Protection and the Static Interrupter.
Canadian Engineer, July, 1902.
Lightning Protective Devices.
Electrical World, January 2, 1904.
Methods of Testing Lightning Protective Apparatus
Proc. Am. Inst. Elec. Eng, June, 1906.
Multigap Lightning Arrester with Ground Shields.
Electric CIuIj Journal, April, 1907.
Performance of Lightning Arresters on
Proc, Am, Inst. Elec. Eng, ITovember, 1905.
Present Status of Protective Apparatus.
Electric Club Journal, July, 1906.
Protection Against Lightning.
Electrical Engineer, September 2, 1897.
Protection Against Lightning for High Potential
Power Transmission Circuits.
Electrical Engineer, September 30, 1896.
Protection of Electric Light Stations from
Electrical World, August 18, 1888.
Protection of Electric Power Transmission from
Electrical Review, London, January 5, 1900,
Protection of High Tension Transmission Lines
from Static Discharges.
Proc. Am. Inst. Elec. Eng, June, 1904.
Protective Apparatus for Lightning and Static
Proc. Am. Inst. Elec. Eng, June, 1906,
Recent Investigation of Lightning Protective
Proc. Am. Inst. Elec. Eng, December, 1906,
Testing Lightning Arresters.
Electrical World, August 4, 1906.
IToveralDer 3, 1906,
Test of Lightning Arresters at "Niagara Palls.
Electrical Review, Hev; York, December 30, 1896.
The Lightning Arrester.
Central Station, June, 1905.
Ahearn Lightning Arrester.
Electrical World, July 7, 1883.
"Ajax" Lightning Arrester.
London Electrician, October 27, 1893.
American Automatic Lightning Arrester,
Electrical World, July 19, 1884.
Argus Lightning Arrester.
Electrical World, April 7, 1900.
Barn's Hot Wire Lightning Arrester.
Electrical World, August 16, 1890.
Barrett Lightning Arrester.
Electrical World, March 20, 1886.
Berg Lightning Arrester.
Electrical ^orld, September 28, 1907,
"Central" Lightning Arrester.
Electrical ¥orld, Peoruary ^5, 1890.
Chinnock Lightning Arrester.
Electrical World, j^arch 13, 1886.
Circuit Breaker Lightning Arrester.
Electrical World, 'Noyeniher 3, 1906.
Condenser Lightning Arrester.
Electrical World, July 8, 1905.
Electrolytic Lightning Arrester.
NovemlDer 3, 1900.
Electrical World, January 12, 1907.
liarch 23, 1907.
Electrcl3'-tic Lightning Arrester.
London Electrician, May 10, 1907.
Electrolytic Lightning Arrester.
Electric Cluh Journal, August, 1907.
Eulmer Lightning Arrester.
Electrical World, July 16, 1892.
Garton Lightning Arresters.
Electrical World, June 20, 1896.
General Electric Lightning Arrester.
Electrical World. July 25, 1903.
Glendale Lightning Arrester.
Electrical World, July 6, 1889.
Gola Lightning Arrester.
Electrical World, June 7, 1902. November 4, 1905,
Harvard Lightning Arrester.
Electrical World, August 12, 1899.
High Tension Alternating Current Lightning
Electrical World, January 16, 1897.
High Voltage Lightning Arrester.
Electric Clu"b Journal, August, 1905.
Horn Lightning Arrester.
Electrical World, ITovember 4, 1905,
Horn Lightning Arrester with Iron Prame.
London Electrician, liarch 7, 1902,
"Jump" Lightning Arrester.
Electrical World, September 21, 1889.
Law Lightning Arrester.
Electrical World, September 29, 1888.
Low Voltage Lightning Arresters.
Electric Club Journal, June, 1905.
Magnetic Blow-Out Lightning Arresters.
Electrical World, May 9, 1896, May 1, 1897.
Mercury Vapor Lightning Arrester.
Electrical World, September 23, 1905.
London Electrician, DecemToer 29, 1905.
Multiple-Discharge ¥6n-Arcing Lightning Arrester,
Electrical World, September 21, 1907,
Non-Arcing Railway Lightning Arrester,
Electrical World, April 14, 1894.
"Perfect Protection" Lightning Arrester.
Electrical World, February %5 , 1890.
Permanent Leak Lightning Arrester.
London Electrician, May 24, 1907.
Quadruplex Lightning Arrester.
Electrical World, June 18, 1892.
Raymond Lightning Arrester.
Electrical World, Foyember 28, 1903.
"Razzle .Dazzle" Lightning Arrester.
Electrical World, March 8, 1890.
Shaw Non-Arcing Lightning Arrester.
Electrical World, May 4, 1907,
Shaw's Lightning Arrester.
Jour. Franklin Inst. November, 1905,
Sperry Lightning Arrester.
Electrical World, Juhe 19, 1886.
Swinging Ball Lightning Arrester,
Electrical World, June 20, 1891.
August I'S, 1892.
April 1, 1893.
Tank Lightning Arrester.
Electrical Review, Hew York, December 9, 1896,
Thomson Lightning Arrester.
Electrical World, September 4, 1886.
Universal ITon-Arcing Lightning Arrester.
Electrical World, September 25, 1897.
Vacuum Tube Lightning Arrester.
London Electrician, December 26, 1902.
Warth's Lightning Arrester.
Electrical World, August 16, 1884.
Water-Jet Lightning Arrester.
Electrical World, October 19, 1907.
Westinghouse Eultipath Lightning Arrester.
Electrical World, June 11, 1904.
Westinghouse Street Car Lightning Arrester.
Electrical World, April 4, 1891.
Wirt Alternating Current Lightning Arrester.
Electrical World, May 8, 1897.
Wirt Lightning Arrester.
Electrical T/orld, May 10, 1890.
Wood's Lightning Arrester.
Electrical World, November 8, 1890.
Woolley Lightning Arrester.
Electrical World, January 5, 1907.
Wurts Lightning Arrester.
liarch 26, 1892.
Electrical World, April 2, 1892.
April 9, 1892.
Wurts-Winsor Lightning Arrester.
Electrical World, July 18, 1891.
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