Hydro-electric power station design

ARMOTTR

INSTITUTE OF TECHNOLOGY

UBRAH.Y

ARMOUR

INSTITUTE OF TECHNOLOGY

LIBRARY

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HYDROELECTRIC

POWER STATION

DESIGN

A THESIS

PRESENTED BY

H. RALPH BADGER

ROY G. GRANT

HAROLD W. NICHOLS

TO THE

PRESIDENT AND FACULTY

OF

ARMOUR INSTITUTE OF TECHNOLOGY

FOR THE DEGREE OF

BACHELOR OF SCIENCE IN ELECTRICAL ENGINEERING

HAVING COMPLETED THE PRESCRIBED COURSE OF STUDY IN

ELECTRICAL ENGINEERING

'LU..«.ouoi ii uit OF TECHNOLOGY / /

PAUL V. GALVIN LIBRARY ■ -f J^>

35 WEST 33RD STREET ^^E^^T^^/ L«_~^ ^^^-^JL

CHICAGO, IL 60616 ~

^J9 C^Ly .<4£^ul\

PREFACE.

The subject of "Jfy-dro-Electric Power Station
Design" has herein "been presented in two parts :-

the first - a brief treatise on the general princi-
ples and important factors, and the second - an
application of these to a particular case.

In Part I. is given a general statement and
analysis of the important factors entering into
the design of such power generating stations.

In Part II. the actual design of a station
for a particular location is undertaken. This pro-
posed station to be located on the Snake River in
the south-central part of the state of Idaho, and
to receive its water supply from the Malad - a tri-
butary of the Snake River.

H. H.B.
R.G.G.

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TABLE OF CONTENTS

Page.

Preface

2

Table of Contents

3

List of Illustrations

4

Part I.

Introduction

6

The General Problem

6

"Water supply

9

Exact Location of the Plant

18

Parts of the Project

20

Power House Equipment

27

Part II.

Introduction

47

The General Problem

47

The water Supply

48

General Lay-out of Project

62

Power station Building and Equipment

52

Transmission of Porer

61

Appendix.

Bibliography

64

Prices and Cost Items

65

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LIST OF ILLUSTRATIONS.

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61
after 60

I.

Map of Idaho

II.

Map of Project

Drawings of station.

III.

Main Floor Plan

IV.

Second Floor Plan

V.

Transverse Section

VI.

Gross Section

VII.

TTiring Diagram

VIII.

Switchboard

IX. Hydraulic Turbine

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Part l«

A Brief Treatise on the General
Principles and Important Factors Enter-
ins Into the Design of Hydro-Electric
PoT?er Generating stations.

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Hydro-Electric Power station Design

Introduction.
A consideration of the subject of "Hydro-Elec-
tric Power station Design" entails a discussion of
the location of the market for sale of power, nat-
ure and extent of the water supply of the source
of power, auxiliary construction for water handling,
location, construction and equipment of generating
station* transmission and distribution of energy.

The General Problem.
Electrical energy is now in nearly universal
demand. The amount of this commodity that is made
use of in any section of country varies within
wide limits. For its common usages - in power and
lighting - this variation is nearly directly with
the population, though there is a constantly incre-
asing demand for it in railway work - outside of
centers of population, with the increased price
of coal, as well as for other disadvantages inhe-
rent in steam production,- other means than indi-
rectly from coal, of generating electric current,

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are "being rapidly sought and utilized. Chief among
theset in present importance, is the water power of
natural sources.

As these cannot he located where wanted - as
can steam plants - hut must he taXen where found,
the general problem becomes one of relation between
location of market for power and the source of pow-
er generation. Ordinary commercial principles
would usually dictate that a power development be
carried forward only after a demand had arisen for
power in a given locality. This is merely a crea-
tion of supply to meet demand. There have "been,
however, in recent water power developments - num-
erous cases of the opposite procedure to this. In
such projects, water powers - especially favored
by location or proportion or both - have been de-
veloped first and the market created afterwards,
in range of transmission. This constitutes a for-
cing demand in such localities - by the creation
of an attractive supply.

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The allowable distance between the point of
generation of power and the point of consumption
is therefore limited by the range of economic and
safe transmission of the energy. As a result of
improving methods and equipment this distance is
gradually lengthening. Present practice does not
much exceed one hundred miles for this as a maxi-
mum figure.

Outside of matters of relative location of
market for power and the source of power supply,
there are several important points to be consider-
ed under the "general problem". First among these
arises the question of the ability of the water
supply to satisfy the market for power; that is,
whether the maximum continuous hydraulic power of
the source is sufficient to meet the demands of
the market. The assumption is made that the "wa-
ter rights" for this amount are obtainable. If
the amount of hydraulic power thus covered is not
sufficient , then the advisability or necessity of

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an auxiliary steam plant must "be considered. Next
comes a consideration of the character of the load
That i3, the purpose for which the power is to be
used,- -whether for lighting, for railway work, for
miscellaneous power purposes or for a combination
of these. If the latter, then the approximate pro
portion of each.

All of these points must be reviewed under a
general survey of a water power development. 7or
further consideration, the more detailed factors
influencing a project must be taken up. These are
outlined in what follows.

The Water Supply.

The very existence of a hydro-electric power
generating station depends upon its water supply.
Obviously then, the continuity and comparative uni
formity of flow of this should be at least reason-
ably assured.

Power sources for such developments at pre-
sent are chief ly confined to the fall and flow of

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streams. The two main factors governing these de-
velopments are the "head" and the volume. The
first quantity represents the difference in eleva-
tion between the surface of the water in the sup-
ply reservoir and in the tailrace: that is, the
difference in height of the water before and after
its potential energy has been utilized. This fact-
or is commonly given in feet. The second quantity
is the flowtor volume of water per unit of time
■vhich is available for use at the given head. This
factor is usually expressed in * second- f eet "- an
abbreviated expression for "cubic feet per second".
The available head, for any project, is -once
it has been decided upon - practicallj' constant.
It may be ascertained by means of a careful topo-
graphic survey of the stream. On the other hand,
however, t&e second factor - namely the flow - is,
owing to the variable quantities upon which it de-
pends*- quite likely to be anything but constant.

It is this factor which gives rise to most of the
difficulties to be met in hydro-electric power sta-

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tion work.

A more careful investigation into the nature
of this quantity - "flow" - will reveal the fact
that it , liable to change from day to day, season
to season and even from year to year. Primarily,
it depends upon the size, contour, vegetation and
soil of the drainage area of the stream, as well
as upon such climatic conditions as rainfall, tem-
perature and barometric pressure. In the calcu-
lation of this quantity both the greatest care and
the most conservative judgement should be used*
Even with these detailed precautions, unusual con-
ditions may arise at times after the project is
completely installed,- conditions of great excess,
or the exact opposite, in the water supply. The
result being that a large proportion of the in-
vestment, possibly the entire amount, will be
rendered valuless. Such serious happenings have
been Known to take place and nothing should be
left undone in the way of precaution. Therefore
all records that it is possible to obtain of the

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flow of the stream in question should he carefully
examined and compared, as well as careful attention
paid to all of the factors influencing it. The ob-
ject of such researches throughout, being to obtain
as accurately as possible, first - the actual mini-
mun that can be reasonably expected from the stream
in point of constant flow, and second, the points of
maximum discharge - together with means of conserv-
ing the energy of such surpluses of water.

Foremost to be considered is the drainage
area. This should be investigated from the source
of the stream and it 3 tributaries to its mouth.
Area, contour, vegetation, soil and rainfall should
be considered. Other factors the same, the larger
the area drained, the greater the "run-off" of wa-
ter. The contour, vegetation and soil manifestly
influence such quantities as absorption of rain-
fall and the evaporation of surface waters - with
a subsequent influence exerted on the resulting
"run-off ". The effect of rainfall on stream flow
is positive though not absolute, as it is greatly

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affected "by the above outlined climatic conditions.
The dry-leather flow of a stream is not so much in-
fluenced by the total annual rainfall as it is "by
the distribution of such rainfall as occurs through
out the year. In this case>as in all cases of re-
lation of rainfall to stream flow* no absolute and
general rule can be formulated, the problem of each
watershed being distinctive. However there are
some considerations common to all cases and these
will be here briefly taken up.

in the first place, what may be termed the
"water year", begins approximately with the month
of December and ends approximately with the Novem-
ber following. This is divided into three periods:
the first six months constituting the "storage"
period, the next three months - the "growing" per-
iod, and the remaining three months - the "replen-
ishing" period. Turing the first period the winte'
snow and the spring rains saturate the ground to a
considerable depth, a large amount of water being

held in storage in lakes, swamps and forests as

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well as in the soils, gravels etc. At this time
in the year a heavy rainfall finds a quick response
in large stream flow, for the saturated ground re-
jects further "water, and the water runs rapidly
from the surface. That part of the stored water oi
this period which lies above the level of the bed
of the stream, within the boundaries of its water-
shed, becomes available for supplying the stream
as well as for the purposes of surface evaporation
and the sustaining of plant life* These waters
will supply a certain part thereof to the stream,
regardless of the rainfall, even maintaining a
flow in the stream for some months without any
rainfall.

During the "growing" period the ground water
furnishes practically the entire supply to the flo
of the stream, the only additional part coming
from an occassional rainstorm. In some cases so
depleted does the ground water become by the end
of August that even a very heavy rain will make no
perceptible difference in the stream flow, the

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ground absorbing the entire amount of the pBBcipi-
t at ion.

During September, October and November the
ground begins to receive its store of water, and
with favorable rainfalls, it becomes saturated dur-
ing the "storage" period following. The stream
flow is a constant drain on this supply, but in ad-
dition to this thare is a loss of water falling on
the watershed due first to evaporation and second '
that amount t ale en up by plant life.

Having thus discussed the subject of Drainage
Area and the influence of its various components on
stream flow, we come to a consideration of the stre
itself. No matter what the more or less theoreti-
cal factors influencing the stream flow may be, we
have finally to deal directly with the actual vol-
ume of water flowing in the stream. To measure
this quantity there are three general methods, any
one of which may be used: the choice, in any case,
depending upon local conditions, the degree of ac-
curacy desired, the funds available, and the length

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of time that the record is to be continued.

The first general field method for obtaining
the value of stream flow is by measurement of the
slope and cross section and the use of Chezy's and
Bitter's formulas: the second method is by means
of a weir: and, the third by measurement of the
velocity of the current and the area of cross sec-
tion of the stream. Where conditions will permit,
the second method offers the best facilities for
determining the flow.

The greater the period of time for which this
data is available,- showing past performances of
the stream under various conditions of season and
climate- the more accurately can its future prob-
able flow be predicted. As it is with this quanti-
ty of "future flow" that the proposed plant will
have to reckon, calculations for it should, if pos
sible, be based on data for at least a number of
consecutive years previous.

A very convenient way of considering this is

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to plat , ifor each year upon which data is availably
a curve showing the relation between the tine of
the year and the flow. The abscissae represent
the days of the year, division points locating the
different months, and the ordinates - the correspon
ing flow in "second-feet*. A scale of theoretical
hydraulic horse power may be marked off on the axis
of (rdinates, this merely representing a constant
times the "second- feet* of flow,- the constant de-
pending upon the "head" and the weight of water.
From this scale may be read direct ly the power pos-
sibilities of the stream at any given tine. A
straight line drawn parallel to the axis of absciss
through the lowest point on the curve, will show
the maximum power to be realized from the stream
throughout the year. If the physical conditions
of the channel and banks of the stream will permit
of the construction of a properly proportioned dam
together with retaining walls (if necessary), then
the whole or at least a part of the water represent
ed by the "peaks* on the time- flow curves may be

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stored up as "pondage", and drawn off at times of
"low water", the resulting maximum constant flow
being thus increased. The comparison of the time-
flow curves for a number of years, on the same strea
will show the variation to expect - at least as
possibilities- from year to year.

From a proper consideration ,then, of the fore
going points - influencing the water supply of a
hydro-electric development - nay be obtained a fair
calculation of the power to be expected from the
source. Prom this we are lead to a consideration
of the exact location of the plant.

Exact Location For Plant.

The approximate location of a hydro-electric
project being determined by means of the factors
of the "general Problem", namely the market for
sale of the energy and the source of the water pow:
there remain but a few points which will decide
the exact location of the plant.

The question of "water rights" must be settle

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By this is meant the obtaining from the State of
the right to use, fM> power generating purposes, a
certain number of second- feet of water from the
stream in question. After this, comes the matter of
real estate on which to locate the power house and
auxiliary water controlling works. This is, how-
ever, usually a minor point as such property is gen
erally some distance from centers of population,
and hence its value is comparatively small.

Outside of these considerations, the exact lo-
cation of the plant should be such as to realize
the greatest efficiency from the two controlling
factors in any project, namely the "head" and the
volume of water. The most available head, consider
ing total fall and the possibilities of back-water,
and the arrangement permitting of the most economic
use of the volume of the water, considering the
desireability or necessity of storage supply - are
the two factors to be sought, with this decided wo
pass to a discussion of the component parts of a

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hydro-electric power generating project.

Parts of the Project.

"With the exact location of the plant settled,
the general lay-out of the auxiliary water controll-
ing works mast be determined upon. The devices
best adapted to conveying the water from the source
of supply to the wheels - form a question peculiar
to each individual case. However, they consist -
in general - of a reservoir, either a part of the
stream or apart from it; a conducting pipe-line
from this to the power house, or in the case of an
open penstock type - a forebay, and, a tail-race,
in this work such parts as dams, intakes, penstocks
gates and tail-races mu3t he considered, and are
here treated of briefly.

Dams.

Por water-power work. there are two kinds of
dams most used - depending upon the material of
their construction, the first - the earthen, and
the second - the masonry dam. Of these two classes

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the failures of earthen dams have been the most
numerous, the cause being either that there was not
the proper length of spillway, or that the outlet
pipes were not properly laid in the dam. The re-
quirements for stability of any dam are that it be
strong enough to withstand the pressure of all wa-
ter that it holds back, that it withstand leaks, and
that it afford proper spillways and sluice-gates.
in the construction of an earthen dam, three
things must be considered: first, the conditions
must be such that the maximum flood that has ever
occurred at the site can be taken care of during
the building of the damjsecond - the water must ne-
ver top the embankment of the dam, - it being eithe
led around the end of the dam or through some new
channel; third - the proper soil should be used
in the construction of the dam. If conditions are
such that the flood waters likely to arise cannot
be carried around the end of the dam during its
construction, then the earthen dam should fcever be

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used*

Any soil used in the construction of an earth-
en dam should he tested for quicksand, and if any
traces are found the soil should he discarded.
Soils having an angle of repose of less than twenty
degrees when placed in water should not he used.
The "best soils for use are those containing enough
clay to give the required water-tightness and "bind-
ing quality,- too much of this ingredient should
he avoided as it swells on becoming wet and shrinks
on drying. If, during the construction the mater-
ials are dampened, cracks and leaks are less liable
to occur. If the material at hand is of different
grades » the best should be placed on thsupstream

side, gradually changing to the more porous toward
the center of the construction.

The profile of an earthen dam will depend upor
the height of the dam. The slopes will depend up-
on the angle of repose of the material used, it
being usual to make the inner or upstream side

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flatter than the outer or downstream side, as earth
when -jet has a flatter slope than when dry.

Where a masonry dam is constructed more atten-
tion must be paid to the foundation than is necess
ary in the case of an earthen dam as any settling
of the masonry will cause craoXs. With high mason-
ry dams the foundations are usually made of solid
rock. The superiority of the masonry over the eart
en dam lies in the facts that it can he made more
durable, can he more precisely designed, and better
protected from flood waters^ owing to the safer
construction it offers for the laying of the outlet
pipes. For all dams of any height , masonry construe
tion is to be preferred.

The shape of a masonry dam will depend upon
the head of water for which it is designed, for lor?
dams the cross- sectional shape usually being trape-
zoidal, but for high heads the sides are usually
curved for the purpose of saving material.

The reinforced concrete dam has some advantag

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that the masonry dam does not possess. It can be
made more stable than a masonry dam of the sane di-
mensions. The materials can be distributed to -bet-
ter advantage and therefore there will be a saving
in cost. The interior of the dam can be inspected*
it can be constructed more rapidly and does not re-
quire such good foundations as do masonry dams. In
many cases where a reinforced concrete dam is con-
structed the power house is built into the dam,
thus greatly reducing the cost of the project.

One factor in the building of concrete and
masonry dams which does not affect the earthen dam
is the effect of ice. In countries having cold
winters the expansion of ice is liable to be great
enough to rupture the dam, masonry more so than
consrete.

"IntaKes" lead from the dam, being either sub-
merged or at the level of the water. The flow
through them being controlled by gates which are
either machine or mannually operated.

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Penstocks.

The cheapest form of penstock is the circular
wooden stave penstock. The staves should be as fre
from knots as possible and should be smoothed on
the inside in order to reduce friction and get the
maximum efficiency. 1Vhere the stave penstock is
installed it is common to have all bends and curves
in the line of steel pipe, unless the curve be of
large radius. Iron hoops or bands are used to hold
the staves in place, their spacing depending upon
the initial tension, the water pressure, and the
swelling of the wood.

Steel penstocks are especially adapted to long
pipe lines, as oft en, in such lines, abnormal press-
ures are developed due to the sudden shutting-off
of the water from the turbines. In order to regu-
late this pressure, a small reservoir is construct e
at the outlet of the penstock, the size of this
reservoir depending upon the time it takes to close
the turbine gates. In place of the reservoir

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a steel standpipe is sometimes used, the water run-
ning over the top of the standpipe if the gates he
closed too suddenly. If the fall of the pipeline
he too great for standpipes, safety valves are plac
©d along the line of the penstock. The life of a
steel penstock is sometimes vary short due to the
rusting of the steel, though this action may be
greatly reduced by treating the penstock with hot
asphaltum. At the entrance to penstocks, racks
should be so placed as to collect all floating ob-
jects and not allow them to pass into the pipe.
In cases of ice formation these racks may become
clogged if the ice is not removed on forming. A
large, deep forebay will remedy this troublB, as the
water,being quiet here, will freeze over at the be-
ginning of cold weather. Then such anchor ice, as
may come into the forebay, will rise to this layer
of ice, while the warmer water will circulate belo-
If the intake to the penstocks be so located as to
receive this water, there will be little trouble
from i~e a^ the racks.

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Tail-race.

This should be deep as it is necessary to have
dead water in the race before the wheels are start-
ed. As soon as water is discharged from the wheels
this will tafce the place of dead water and thus
there will he no resulting loss of head. It is us-
ually necessary to place the wheels at some height
above the tail-race, the water after leaving the
wheel passing through a draft tube. This draft
tube should be air tight and submerged - at its low
er end - in the water of the tail-race to prevent
any loss in head.

Power House Equipment.

Water v/heels.

These may at once be divided into two classes -
impulse wheels and turbines. The former is typi-
fied by the Pelton Company's wheel, in which the
velocity of a Jet of water impinging tangent ially
upon a disc, carrying buckets around its periphery,
transmits to the buckets a part of its velocity.

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It can be shown that the efficiency of the trans-
formation is a maximum when the velocity of the mov
ins buckets is one half that of the jet, so that if
H is the effective head of the source, for maximum
efficiency, the peripheral velocity of the wheel is
related to the head by the expression:

▼ « r= .5 /glT

and the head being assumed invariable, it is seen
that for a certain definite speed (imposed by the
frequency of the generator), the only variable is
the diameter of the wheel and this may be adjusted
within cdrtain limits, to conform to the relation
above. Thus direct connection of the generator
to the source of power is possible, which eliminate
the losses in transmission through gearing and the
noise incident to its use.

These -"Theels require that there be sufficient
distance between the wheel and the highest point of
backwater, to allow for the discharge of the spent
water from the buckets of the apparatus, and for

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a variable height of hack water at different sea-
sons of the year, this involves a serious loss of
head. Also, since the action of the machine depend
upon the velocity of the Jet, which in turn depends
on the square root of the head, the Pelton wheel
is only available with any great efficiency when
the head is great, i.e. above three hundred feet.
In general, then, its use should not be considered
with heads less than this.

Water turbines are available for the lower
heads, since they do not depend entirely upon the
velocity for the necessary Kinetic energy - the
large mass of water obtained may reduce the necess
ary velocity. These machines are typified by the
products of the James Leffel Co. , the S.Morgan Smi
Co. and many others. Under favorable conditions
they give an efficiency of from eighty to eighty-
two percent , and may be obtained in the horizontal
or vertiole form. The verticle type, on account
of the reduced friction losses caused by the lesse
ed friction in the bearings, gives an efficiency

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about three per cent higher than the horizontal
type, exclusive of gearing, hut due to the fact
that gearing is necessary to change the direction
of motion, involving a loss of about ten percent,
the actual net efficiency is reduced approximately
seven percent unless the generators are of the ver-
tical type also. Horizontal wheels are favored
because they permit the use of several units on one
shaft, and if this number is even, the unbalance
of pressure caused by one unit i3 taken up by the
next so that the friction loss is diminished. In
order that vertical units may actuate one shaft,
this shaft must be horizontal to conform to prac-
tical conditions and the use of vertical generators
as was noted above, is precluded, and there is also
introduced the loss due to the gearing which must
be installed*

In choice of prime movers it is therefore
necessary to consider:—

1. The available head, which will determine
practically the availability of Pelton or tufcbine

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wheels by the condition that for heads above three
hundred feet the Pelt on wXeel is to be preferred,
for heads less than ^wo hundred feet, the turbine,
and for intermediate heads, either one indifferently.

2. The type and speed of the units and their

capacity, since for generators of large size it may

be necessary to install several units on one shaft,

which involves the difficulty mentioned above, and

1
the restrctions that limit the generators of the

horizontal type.

3. In addition to these conditions, which
must hold generally, others are imposed when the
head is not constant, that is, when the backwater

is variable. In this case the velocity of the wheels

will not be constant, and since the generators are

practically constructed to operate at a constant

frequency, this variation could not be allowed, even

if the field rheostat of the machine were capable

a
of taxing up the increase or decrese of pressure

at the terminals. Also, since a decrease in speed

will decrease the output, it would be necessary,

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Itydro-Electric Power station Design

even in the above case, to install a gseater cap-
acity than would be required at the normal full-
load speed and tche disadvantages noted would still
be present,

in this case it is necessary to install another
wheel is geared with a higher ratio to the line
shafting so that when the head is decreased this
wheel may be thrown in with the other one, their
speed then being a mean between the two and the
decrease in output of the first being supplied by
the second. If the variations in head are very
wide, it may be necessary to install several of
these additional wheels and allow them to run idle
during the normal operation of the plant. This
extra installation of course involves a higher first
cost and is to be avoided if possible.

In the choice of the number of units there
should be considered the over load capacity of the
units so that when one is disabled or shut down
the remainder of the plant may carry the load with-
out exceeding the allowable overload rating of each

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unit, it is common practice to decide on this rat-
in* as 33$, and it then follows that four units
are necessary since on may then be cut out and the
re- 6 can carry 33$ overload and maintain the nor-
mal ouput of the plant.

Generators! — The first classification of gen-
erators is into the direct and alternating current
machines, and the choice is determined "by the char-
acter of the load and the transmission distance.
Ws assume that this distance is not short enough
to warrant the use of direct current, and proceed
to consider the features which determine the choice
of alternators. The problem for di»ect current
transmission is much simpler, and nay be solved
by neglecting the factor of frequency.

The conditions determining the frequency are
the character of the load and the transmission;
for example if the power is to be supplied to
svnehronous converters the frequency should not
exceed forty cycles, and to conform to the apparatus
already in stocR in the manufacturing concerns,
this figure should probably be chosen at twenty-
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This is also suitable for transmission and power
service, but has the disadvantage that incandescent
lamps do not operate well at this frequency so that
if the lighting load 4s not concentrated in cities
where it may be supplied by synchronous converters
it may be Aecessary to install frequency changers.
At sixty cycles' this difficulty would be avoided,
hut converters do not operate at this frequency
with any great stability, and the conditions of
constancy of service demand that the substation
operation be as nearly perfect as possible.

If it is found desirable to use this higher
frequency, induction motor-driven generators may
be installed for the conversion to direct current,
but this eliminates the possibility of compensation
for lagging current in the line, and this difficulty
may be of considerable magnitude if the line is
to supply power to induction motors along the right
of way.

A careful consideration of the load to be sup-
plied will therefore be necessary in order to deter-
mine the frequency at which the current is to be

supplied. Page

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The voltage to be generated by the machines

is of little importance if it is to stepped up

e
for transmission, so that this fact must "be dter-

mined. The highest voltage at which it is practic-
able to generate is about 11,000. in deciding upon
the transmission voltage it is common practise to
figure roughly upon a thousand volts per mile
within the limits of safety, which is set at 80,000
volts in this country* we therefore decide that
if the distance to which power is to be transmitted
exceeds ten or fifteen miles it will desirable to
stop up the pressure and generate at such a potential
that the insulation of the machines will not be
in danger nor will the armature be forced to carry
excessive current.

It having been decided in the preliminary in-
vestigation what will be the capacity of the plant,
the next step is the division of units. The same
conditions which govern the nia&nber of prime movers
apply here and we may state that there should b«
at lea»» four units, a greater inumber being of course
necessary when the output of the plant is so great

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that four units of the largest commercial size 7d.ll

not carry the load.

We now have the frequency and capacity of the

generators and desire to Know the speed at which

they will operate. This speed is limited to certain

definite values by the limitation to constant frequency

so that the r.p.m. must satisfy the relation:

60 f / p a n

where p is the number of pairs of poles and f the

frequency. From this relation the following table

may be made showing the number of poles for each

speed to give the desired frequency and the catalogs

of the manufacturers may then be consulted to d.b-

termine the machine to use. Before settling upon

a unit the peripheral velocity of the rotating parts

should be calculated in order to ascertain if this

value is too high for the safie operation of the

machine* if this is the case it will be necessary

to choose a machine with a greater number of poles

and a slower speed.

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The generators should if possible be direct-
connected to the prime movers to eliminate any fric-
tion losses in the transmission and this fact neces-
sitates a consideration of the speed of the wheels*
Thi3 speed is determined by the effective head, and
in trhe case of the Pelt on wheel it was shown that
the diameter of the wheel could be varied withinn
certain limits to compenstae for any disagreement
between these twp speeds. In the case of the tur-
bine, however, this compensation is not always pos-
sible, although the manufacturers have in stock a
great variety of wheels which will generally give
the desired relation. If this cannot be obtained
it will be necessary to gear the wheels and the
generator can then be made to run at any speed,
the desired frequency being obtained, by the ratio
of the gears-
Exciters:— From two to three percent of the
output of the plant is required for the excitation
of the units, so that this much mist be added for

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the gross output of the plant if the initial cal-
culations are sufficiently close to warrant con-
sideration of Quantities of this magnitude. The
exciter plant is the weaX linh in the system and
great care must "be exercised in the installation
of the units. Several facts may be noted In this
connection,

lm There should he two independent sources of
excitation which may be readily interchanged so
that in the event of one "becoming disabled the
operation of the system may not be suspended for
anyconsiderable period.

2. Tfte prime movers or other apparatus driv-
ing the exciters should al#> he independent and
capable of operating in parallel so that in the
event of the failure of one system the other may
be automatically thrown into service without the
delay incident to the manial operation of the
necessary switches* By this is meant that the
exciters should be provided with reverse current

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relays so that in case one of the prime movers
fails and the generator thereby becomes motorized
the other may pick up the load while the first is
automatically cut off from the exciter bus. His
means that each system must be capable of carrying
all the excitation necessary for the plant at any
time, and since the breakdown of apparatus usually
•ccurs at times of heaviest load, this consideration
is of fundamental importance. In water-power sta-
tions the sources of power may be water— driven
wheels for the operation of one system and motors
for the other. In this case the motor-driven ap-
paratus must be kept constantly in operation, since
if this were not the case the failure of the water-
driven exciters wo't^d disable the plant. At times
of light load, however, it will be safe to operate
the plant with but one set of exciters, since the
possibility of the break-down of apparatus is slight
and more is to be feared from the mistakes of the

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operators than from faults of the machines.

Transformers: — it having been decided that
there -grill be a definite number of phases — usually
three— arid the transmission voltage baling known,
the transformer problem becomes simply a phoice
between the adoption of three single-phase trans-
formers connected up to give the desired relation
of e.m.f's or one three-phase transformer for
each unit. The conditions influencing the choice
are as follows:

1* The distance from the nearest shipping
point to the power station — this enters in because
of the fact that large transformers are more dif-
fi cult to handle than small ones, and if, as is
usually the case, the power house is located in a
mountainous country, the smaller units would pro-
bably be chosen, since the cost of transportation
will overbalance any saving in first cost.

2. The facilities for the handling of the
apparatus at the "newer station, such as cranes,
labor, etc. The use of the larger units of cduree

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makes necessary a larger crane.

3. The necessity for a spare unit. In the
case of three single phase unit 3 the connection
may be so made that any one of the transformers in
the station may be disconnected if injured and the
spare put in it 3 place by means of air-break dis-
connecting switches. If three units are employed
a three phase unit may be usdd as a spare and the
increased cost would make an installation of the
single phase units desirable. TSiis consideration
vanishes when the size of the station is great or
the units numerous, since the additional compli-
cation of circuits due to the installation of
disconnecting switches more than balances the extra
cost of the three phase unit.

4. If one of the single phase units becomes

burned out it may be removed, but in the other

case the whole transformer will need to be removed

unless it is connected delta and allowed to operate

with a v-connection at 58$ of its firmer output.

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The large units are in general desirable if
the objections mentioned above do not operate,
for they are more compact , all the coils in one
case and the installation is less complicated, also
the first cost is less. A disadvantage is,, that
since the surface of a tr nsformer and its output
do not vary uniformly, but the surface less rapidly,
the cooling of the larger sizes will be a more sftr—
ious problem. This however may be accomplished
quite readily by the use of fans for circulating
the air through the coils»

Instruments and "firing: — These switchboards
may be separated into two parts, the exciter board
and the mainboard, and these may be concentrated
in one position or separated, according to the size
of the station. When the size is sufficient to
warrant the constant attention of two operators,
the exciter board may be isolated and loeated near
the exciter units, the other being placed in a
gallery, fhen this arrangement is adopted one op-
erator may take charge of the exciter board and
look after the units on the main floor while the

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other confines his attention entirely to +'ie opera-
tion of the lines and units, where theplsat is
used to supply a large number of lines it is pre-
ferable to have the oil switches located in a room
by themselves with an attendant there to unlock
them, preparatory to their closing, at a signal
from the operator in the gallery. This eliminates
the danger of closing a dead machine on the line
or other machine by mistake.

This segregating of switchbords and swithhes
makes a more expensive construction and where the
first cost is anitem, or where the plant is small,
the switchbords should be concentrated. In hydro-
electric plants, where the lines ire in general
long ones, and this fact precludes the possibility
of a large number of them, the operation of the
lines will not be necessary more than perhaps once
a day, so that the above mentioned precautions need
not be taken in their operation.

The following instruments should be located
on the main switchboard* For each generator panel,

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Hydro-Slectric Power Station Design
three ammeters, three indicating wattmeters, ene
voltmeter with selector switch for each phase, one
integrating wattmeter, and one field ammeter.

The switches and auxiliary apparatus shoild
comprise: An oil switch control for thrwing the
machine to H.T. "bus, generator field switches,
and a field rheostat control. The field switches
should he equipped with a clip for short-circuiting
the generator fields through a resistance when the
switch is opened, thus avoiding the introduction
of stresses into the windings by the induction of
a high potential at that time.

The exciter equipment should consist of an
ammeter and voljrmeter for each unit, swithes for
throwing the exciter to the exciter bus, field
rheostats for the voltgge regulation, and the
necessary equipment for the operation of the prime
mover* If this is a motor there should he an in-
tegrating wattmeter to register the power consumed
in excitation. Equalizers should also be installed
if the exciters are compound wound and designed to
operate in parallel.

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Itydro-Electric Power Station Design

On the high tension side there should he over-
load relays on each phase* actuated from series
transformers and esigned to open the generator switch

at any desired overload and after any desired in-
terval. These should he of the bellows type*

In the station some kind of frequency limiting
device is necessary to trip out the machines should
they have a tendency to race beyond control. This
may be of the inductive balance type or purely me-
chanical, and a common practice is to design the
instrument so that it will operate at a frequency
ten percent above normal. This values seems somewhat
low for isolated plants, and fifteen percent would
appear to be better.

Governors actuated ey an electrical connection

with the load ammeters have been suggested in order

to eliminate the time necessary for the system to

change in speed, but the idea has not as yet been

tried, and seems not to find favor with the designers

of these plants.

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AHMOTTR

INSTITUTE OF TECHNOLOGY

LIBRAKY

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Part II.

Design for Proposed Hydro-
Electric Power Generating station,
Malad River, Idaho.

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Kydro-Electric Plant,- Malad River, Idaho

Introduction.
In undertaking the actual design of a hydro-
electric power plant, it was desired to have as
near worXing conditions as possible- The selec-
tion of the location on the Malad River, Idaho was
made after data had been secured which gave the
exact conditions that existed at this point.

The General Problem.

The source of the power for the proposed plant
is from the Malad River - a tributary of the snaXe
River: the two meeting in the western part of Liiv-
coln county, which is located in the south- central
part of the state of Idaho.

The present marXet for power from this source
is that offered by the city of Boi3e - for light
and power- a hundred miles distant: the town of
Glenns Perry - principally for light - thirty miles
distant: and locally, within a radius of from five
to ten miles - for irrigation pumping purposes.
A possible future marXet consists in certain rail-

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Hydro-Slectric Plant,- Malad River, Idaho

road electrifications that have been proposed in
the vicinity.

No continuous record is available on the flow
of the Malad River* but from such readings as have
been taken of this quantity, it 13 evident that
there is a uniform volume of water in the stream
highly sufficient to carry a plant of 4800 kw. -
ouch as is here proposed. This allows for the di-
version of small quantities of water for irrigation
purposes, these being protected by existing water
right s.

The ^ater Supply.
The Malad River is supposed to be the outlet
for both the Big ^ood and the Little ^ood Rivers.
These latter rise on the southern slopes of the Tetan
Mountains which form a water shed extending along
the northern boundary of Blaine county, Idaho. Prom
here the rivers flow southward, fed by numerous
smaller streams,- a distance of some hundred and
fifty miles. At this point they join, disappearing

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from the surface of the earth. Ten miles farther
on the Malad RLver rises - being the accumulated
waters of thousands of springs. The theory being
that the Wo rivers - the Big Wood and the Little
Wood - after leaving the surface, traverse a sub-
terranean passage which terminates under the springs
which form the nucleus of the Malad River. The
water of the Malad is a constant in temperature
almost throughout the entire year, this being at
about 60 Ph. The course of the stream, from the
springs that form its source, lies through a box
canyon about three miles in length - to the south
west, where the Malad empties it3 waters into the
SnaXe River.

The drainage area of the Big Wood and Little
Wood Rivers constitutes what is Known as the "Big
Camas Prairie", which lies chiefly in Blaine and
Lincoln counties. The rainfall over this area is
fairly uniform in its distribution. The walls of
the box canyon through which the Malad flows are
composed of lava and basalt rock. For a short dis-

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Hydro-Electric Plant,- Malad River, Idaho

tance its banks arecovered with volcanic dust over
which there is a sparse growth of sage brush.

The General Lay-out,
A reference to the "Map of Project *, shown in
the second illustration, will give an idea of the
general lay-out as designed. At a point,* mile
and a quarter from its Junction with the snake
Hirer, a dam is to be constructed across the Malad.
An intake located here leads into an open channel
through which the water is conveyed to a reservoir,
from which it falls to the power house through a
circular steel penstock. 4 spillway is located
at the reservoir - for discharge into the Snake
River direct. A controlling gate is located at
the head of the penstock.

Power House.
The power house is to be located on the bank
of the snake River. In construction it is to be
two stories in height, of concrete throughout. The
foundations consist of layers of concrete resting

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Ifydro-Electric Plant,- Malad Hiver, Idaho

on bed rook.

Equipment •

Water-wheels, unlike electrical apparatus,
are not rated to carry ally overload, ao that any
that is necessary to allow the shutting down of
one of the units must he provided by installing
wheels of the maximum capacity to be obtained at
any time. The capacity of the station being 4300
kw. , the installation will therefore be of four
2000 H.P. wheels, thus allowing an overload capa-
city of the desired amount. After considering the
various types of wheels it was decided to adopt
the type manufactured by the James Leffel company.
These aroof the horizontal type, direct-connected,
and are especially designed for the head considered-
185 feet. The efficiency at full load is found
to be 89$, at three-fourths load 83$, and at half
load 75$. The maximum efficiency is therefore ob-
tained at the output of the apparatus which corres-
ponds to full load on the generators, and any over
load will somewhat lower the efficiency.

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Itydro-Electric piant,- Malad River, Idaho

The diraemsions over all are eighteen feet by
seven feet, eight inches, the diameter of the in-
take sixty inches, and of each of the tw0 draft
tubes - at the lover end - forty-eight inches, and
at the outlet - thirty-t?ro inches. Details of these
wheels are shown on Drawing No. Till.

Due to the peculiar advantages of the ground
lay-out it is decided to bring the water into the
power house overhead, by means of the large pipes
shown in the drawings. These derive their power
from the main penstocks, which is eleven feet in
diameter at the outer end and narrows down to five
feet for the last unit.

The governors used are of the standard type B -
Lombard, and are purchased with the turbines. These
operate by means of a mechanical connect ion with
the units instead of by means of an electrical con-
nection wi th the ammeters, as has been suggested in the
first part of this paper. The estimated loss of
time in their operation is approximately one second
and is due to the large amount of inertia of the
rotating parts, further loss of time is eliminated

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Hydro-Electric Plant,- Malad River, Idaho

by the installation of a reservoir near the station
of sufficient capacity that the water level will
never fall appreciably when a sudden demand is made
for power. The time taken for the pulse to reach
the station from the d*m will he the distance divided
"by the velocity of sound in water.

Choice of generators is largely a natter of
persons opinion, since the output of the large
manufacturing companies is of a high degree of ex-
cellence. Due to the restrictions on the frequency
noted above, this figure waa taken at twenty-five
cycles. The speed is therefore limited to the values
given in the first part of this treatment under
the head of Electrical Units. The values are, 300,
375, 750, etc. Since direct-connection with the
water wheels is desired » the speed which was decided
upon was 375 r.p.m. in order to conform in speed
with the water wheels selected. This is a standard
machine fori the capacity wanted - 1200 Xw. -
so that no trouble was experienced due to too high

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a peripheral speed.

The transmission distance ( maximum) is one
hundred miles, so that there will be the necessity
of stepping up the voltage for transmission, and
the pressure of the machine is immaterial within
wide limits. This figure was taJcen ai> 11,000 volts
for the following reasons: Part of the power is
to be transmitted a distance of thirty miles and
it is desireable not to retransform this power from
the extremely high voltage for the longer transmis-
sion. The machines are therefore connedted direct-
ly to a "low tension* bus, at a pressure of 11,000
volts and the power for the shorter transmission
istaken from this bus» while the transformers are
fed from the 11,000 volt bus and transform the
pressure from that to the value required for the
longer distance.

Since the rough approximation for the trans-
mission voltage demands a pressure of 100,000 volts,

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and this is at present beyond the capacity of the
insfclators available, the voltage decided upon was
66,000, giving a value of volts per mile as 660,
which is in accord with modern practice.

As was noted above, it is necessary to have
two independent sources of excitation, and this is
accomplished by means of the motor-and water-wheel
driven units shown in the drawings* Greater
dependence will be placed on the water-wheel-driven
apparatus, so that two of them are installed and
the motor—driven unit is to "be used in emergencies,
and to run in parallel with the others during the
peak load or at times when a shut down would be
most disastrous. 3ach of the exciter units are of
75 kw. capacity and the motors and ^ater-wheels
of 100 HP each. The power for the motor-driven
exciter will be derived from a transformer fed
from the "low tension" bus, the e.m.f. oeing step-
ped down from 11000 to 22o volts. "Die motor is
of the induction type and is started by means of

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the special starting taps shown diagramraatically
in the wiring diagram. This dispenses with the
necessity for auto-transformers* and the more
expensive construction entailed. It will he ne-
cessary only to bring out two additional leads
from the secondary of the transformer, and since
this may he located at no great distance from the
exciter, the expense will he small compared with
that incident to the use of an auto-transformer.

By thus dividing the units there is no danger
that the excitation of the fields will be lost at
any time except under the most extraordinary con-
ditions. These precautions are necessary due to
the fact that the exsiter system io the weaXest
part of the plant and the greatest care must be
taken in its design if continuity of operation
is expected.

The conditions influencing the use of singlf
or three phase transformers were noted above. In
this case it was decided to. install single phase

units due to the fact that the country is rough

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Hydro-Electric Plant, — Malad River, Idaho

and the distance to -which they must be transported
is rather large. It aloo makes necessary the in-
stallation of a comparatively cheap unit only, this
being placed somewhere on the floor of the trans-
former room and connected in as desired by means
of flexible leads.

The capacity of the transformers will be ten
percent greater than that of the generators to con-
form with common practice, 30 that each unit must
be rated at 440 lew. These are to be connected up
delta on both sides. This is also an additional
safeguard, since in this case if one of them becomes
burned out , the other set can then caryy 58$ of
the load with the same heating by operating on a
V-connection, and, the continuity of the service
need not be interrupted during the time necessary
for the installation of the spare unit.

On account of the character of the load the
operation of the lines Trill not be necessary more
than once or twice a day and therefore attendance

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of an operator on the switches will not be neces-
sary. These switches should be located , however,
in another room to protect them ffom the dampness,
and to insure their proximity to the high tension
buses. For this reason they are to be located up*
stairs where they can be readil3r reached from
the lower floor by the two stairways. The high
tension buses are also located fcere so thata
minimum amount of copper is required. The two buses
run parallel throughout their length, asshown, and
this makes it possible to extend the plant at any
time by merely tearing out the end -alls and instal-
ling a new unit. The buses can then be extended
also and the station will then be symmetrical as
before.

The drawings showing the arrangement of the
above specified apparatus and machinery are repro-
duced in the following pages.

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ARMOUR

INSTITUTE OF TECHNOLOGY

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DRAWINGS
for proposed
HYDRO-^SOTKEC VO^im PLANT
Malad River,
Idaho.

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Itylro-Electric Plant — Malad River, Idaho.

Transmission of Power: — There are to be two
36000 volt three phase, twenty- five cycle transmis-
sion lines from the plant to Boise City and to
Glenn's Perry, Idaho. In addition there are two
11000 volt lines to supply po"-er for public pur-
poses in the vicinity of the plant. The calcul-
ations for the 66000 volt lines follow:

Boise City line, 100 miles long, 3200 kw.
to be transmitted, transmission voltage, 66000

Line loss
Res. per wire
Sixe of wire
Distance between wires
induct anoo per wire
Capacity to neutral
Natural frequency
Charging current
Ind. reactance
Cond. reactance
Reg. no load

256 kw.
109 ohms,

• 3 Band S.
61— 6"

• 21 henry s
1. 36 x 10"
470 cycles
8.2 amp.

33 ohms
4670 •

• 374fj

3

f/mile

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Hydro-Electric Plant,- Malad River, Idaho

Reg. full load

8.1 $

Reg. 85$ power facto?

4.3 #

Wt. copper

252,642 #

Spacing of poles

45/mile

Number of poles

4,500

Glenn's Perry

Line.

30 miles long, 800Kw.

Transmission voltage

68,000

Line loss

1.8 $

Resistance per wire

97.5 ohms

Sise of wire

#8

m stance between -wires

6' - 8"

Inductance per wire

.068 henrys

Capacity to neutral

-8
.375 x 10

fAii:

Natural frequency

1,570

Charging current

2.25 amperes

Ind. reactance

10. 6 ohms

Cond. reactance

17,000 ohms

Reg. full load

♦ 05 cp

Reg. 35$ power factor

.08 <jo

Number of poles

1,350

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APPODIX

Hydro-Electric Power Station Design.
BIBLIOGRAPHY.

Hydro-Electric Power Plants; Beardsley.
Transmission or Water Power; Adams*
Standard Handbook for Electrical Engineers; MeGraw
Water Supply Papers; U. s. Geological Survey.
*Totes and Designs on Hydro-Electric Power Stations,

American Institute E. E. , 25:163, Apr.06
Location of Electric water Power Stations,

Gassier 3, 25: 498.
Electricity from Water Power,

Elec. Eng. , 34: 294
Modern Power Plant Design and Economics,

Eng. Mag., 88: 689, 812.
■ ■ 30: 71, 182.

Use of Pacific Coast Water Powers in Electric Op-
eration of Railroads,

Jour. Elec. , 15: 115.
Sixth Biennial Report , 1905 — 8

State Eng. Idaho.
Water Power" of the Rock River: Mead.

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J^rdro-^ectric Power Station Design

PRICES and COST ITEMS.
(Malad River Project)

Hydraulic Turbine Units-
Including draft-tubes and type "3"
Lombard Governor. Gross weight about
75,00 pounds. P. 0,3. cars at factory,
each -

$ 7,800.00

Steel Penstock -

Circular in form: of riveted steel
plates, with necessary saddles and
stiffeners. Per lineal foot (about ) -

6 46.00

Wooden stave pipe at about half
this figure.

Nearest railroad connection - at 31iss, Idaho (three
and one-half miles) : Oregon Short Line.

Freight rate to this point, from Chicago,
on eledtrical machinery about 1 1/2 cents
per pound. The rate on structural steel
from Pueblo to Bliss,- about 75 cents a
hundred.

Cement : about $3.35 a bbl. , f.o.b. Bliss.

Sand, rock and gravel to be had on the work.

Suitable poles for the transmission ( thirty-
five to forty feet long) can be had on the
work for about $5.00 per pole.

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Hydro-Electric Pcver Station Design

Market for poirer -

Transmitted and districted to
Boise - 100 miles,- 2-1/2 cents
a lew. hour.

To Glenns Perry - 30 miles, -
5 cents a kw. hour.

For pumping purposes in vicinity
of plant,- 1-1 /s cents a tar. hour.

Transmission Lines.

To Boise (100 miles) -

Cost of copper $ 37,296.00

• ■ poles 18,900.00

cross arms 3,150.00

insulators 23,625.00

—^ rr onri r\r\

pins

Total

7,200.00
$ 90,171.00

To Glenns Perry (30 miles) -

Oost of copper I 3,566.00

* ■ poles 5,670.00

" " cross arms 945. 00

n " insulators 7,088.00

■ * pins 2,160.00

Total I 19,429.00

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