ARMOTTR INSTITUTE OF TECHNOLOGY UBRAH.Y ARMOUR INSTITUTE OF TECHNOLOGY LIBRARY < ■ ■ - 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 ~ ^J 9 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. Page 20755 2 3X1 • I ' UB<3 I 1 r i - ■ - , - . . . . 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 Page 3 ! LIST OF ILLUSTRATIONS. Page 49 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 Page 4 - - Part l« A Brief Treatise on the General Principles and Important Factors Enter- ins Into the Design of Hydro-Electric PoT?er Generating stations. 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, Page ! - i - ■ ■ - Itydro-Electric Power Station Design are "being rapidly sought and utilized. Chief among these t 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. Page 7 - - - ■ ■ - ( Hydro-Electric Power Station Design 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 Page 8 - - - ■ Hydro-Electric Power Station Design 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 P| ? e ■ • - - - - Hjrdro-Slectric Power station Design 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- Page 10 - - v :•■ i * - - ... Hydro-Electric Power Station Design 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 Page 11 - lis Hydro-Electric Power Station Design 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 Page 12 I ... - ■ - ■ Hydro-Electric Power Station Design 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 Page 13 .... I . ■ ... Hydro-Electric Power station Design 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 Page 14 I ■ - - i Hydro-Electric Power Station Design 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 Page 15 ■ I ■ ; • : i Jtydro-Electric Power Station Design 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 Page 16 - : : : to 2tRb ■ :it eicfB ■ ■■■ - Hydro-Electric Power Station Design 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 Page 17 . - - ■ i ■ " Jtydro-Electric Power Station Design 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 p !f e I - ■ - c 1 - ■ - Ifydro-31ectric Power station Design 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 p !i 8 - I ■ - - Hydro-JSlectric Power Station Design 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 p ?S e - ■ i ) , ■ • i - Hydro-Electric Power Station Design 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 Page PI - - ES0 - ."-:'■ i - - be! i Hydro-KLectric Power station Ttesign 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 Page 22 YifA - ' - - err? i ©if* ■ i ! Hydro-Electric Power station Design 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 Page 23 - ■ ■ ■ - ft ■ I •Xb ! Ifydro-Slectric Power Station r^ign 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. Page 24 ■ I ■ - ■ ' Hydro-Electric Power Station Design 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. 1 Vhere 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 Page 25 ■ ■ ■ ' ■ - Hydro-Electric Power station Design 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. P 1P - , t - ... . ■ - Hydro-31ectric Power station Design 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. Page 27 r ex.* ■ -• ■ ■■ - - Hydro-!31ectric Power Station Design 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 Page 28 - I : i ■ tit b erff ■ i i • ■ Hydro-Electric Power Station Design 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 ?axe '85 ■ • • •■ ' I . • ■ ■ ... ■ . tjhr lev ■ i '«* Hydro-Electric Power station Design 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 '§6< otfc ■ ; • '■■'.. ..• . I - #jb©lli8^anl mil rrl — : Hydro-Electric Power station Design 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, Page 31 • ' on i " ■■■•■■ | | ©Id 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 Page 32 - a ,( m ■ ■ ■ ■ - Hydro-Blectric Power Station Design 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- five* Page 33 - I ; ■ Itydro-Electric Power Station Design 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 34 ■ ■■ • . ■ ! ■ « - ■ Hydro-Electric Power Station Design 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 Page 35 - - - i :. its ■ Hydro-Slcctric Power Station Design 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. Page 36 : ... - -3 [it to i I • Hydro-Electric Power Station Design. 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 t r he 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 Pag© 37 - - - ■ i . ■ £ i 'iro HSrdro-Electrio Power Station Design- 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 Page 38 ■ .... bnc -ox* ■ art J h o£cf«f.: i - ■- - e<JB • ■ Urdro-Eldctrlc Power station Design 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 Page 39 . ■ : wi±e mm i « ■ Hydro-Electric Power Station Design 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 Pag« 40 - ' - : i .... - - - y ■ - : ... Itydro-siectric Power station Design 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. Page 41 I - ■ I Hydro-Electric Power station Design 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 Page 42 ■ - es I J$rdro-Slectric Power Station "Design 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, Page 43 ■ I we bt\B - i - . <- - - 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. p lf e - - ». ■ BJ ■ i e ni: 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. Page 45 AHMOTTR INSTITUTE OF TECHNOLOGY LIBRAKY ■ ■ ■- ■ ' i ■ i .. ,.ifj . » Part II. Design for Proposed Hydro- Electric Power Generating station, Malad River, Idaho. ; . - 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- Page 47 es or; ■ : ■ : : ■ : 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 Page 48 ■ - ■ Hydro-Blectric Plant,- Malad River, Idaho 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- Page 50 ■ - I ■ • ■ I '■'■ ■ ■ 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 Page 62 ■ ■ •ULfOt 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. Page 53 -t i • TO? J36C ■ &»£87 Jon er* atfir is - ■ - • - . Itydro-Electric pi an t,- 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 tw 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 Page 54 ■ ■ it ■ it tB metetnatb ■ aqo ■ .■ofccf 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 Page 55 - - • ■ - I - Hydro-Electric Plant,- Malad River, Idaho 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, Page 66 • ■' ■ ■ - oi: - l - Hpdro-giectric Plant,- Malad River, Idaho 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 Page 57 I, -- - I ■ - ■ - b&J. ! Ifydro-Electric Plant, — Malad River, Idaho 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 Page 68 ■ - ■ ■- . • B88*« ■ ■ S. : ." :b &t£cw 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 Page 59 • ■ t*»LJ to ■ ■ - •■ I ■ I - nO ac Hydro-Electric Plant , — Malad River , Idaho 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 readil3 r 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. Page 60 ARMOUR INSTITUTE OF TECHNOLOGY LIBRAS? I ,1 - ■ ■ l ■ - - DRAWINGS for proposed HYDRO-^SOTKEC VO^im PLANT Malad River, Idaho. jE . . 1_Ll .. . ( ::: 1": :: : : rr: c: he: he: ixo: n i he :: he: he hed vvv' ii <D (LJi he C Ol 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. 6 1 — 6" • 21 henry s 1. 36 x 10" 470 cycles 8.2 amp. 33 ohms 4670 • • 374fj 3 f/mile Page 61 : ' - ■ ! am . ■ - . . . . D 88 . ■ . *■ 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 c p Reg. 35$ power factor .08 <jo Number of poles 1,350 Page 62 . , ' - - . , ' ' • ' . ' . . . . . . - 1 ■'! . * . . . ■«-t 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. Page 64 1 ; ■ : : ■ ■ ■ 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. Page 65 * . ■ : to*! lee . .. . . . , , ; ©f • . fit 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 Page 66 - 3 - - v - -: 1 --. "*> / m ' >■'<*$ ut» JfV , «• Yflpfe 1^-i'