electrical design features of waukegan station

Electrical Design Features of WaukeganStation

BY E. C. WILLIAMS*MAlember, A.I.EE.

T HE Waukegan Station of the Public Service Com- the use of metal-clad switchgear for the 12,000-voltpany of No. Illinois is located at the north limit of equipment, and for the 2,400-volt and 480-volt auxiliarythe city of Waukegan on the west shore of Lake equipment. Fig. 3 shows the 12,000-volt, type M

Michigan. This steam generating station is the chief switchgear.energy supply point between the Illinois-Wisconsin The bus arrangement of the 12,000-volt metal-cladState line and Chicago. It also forms one of the supply switchgear used for units 3 and 4 is somewhat of a de-points for the Company's 132-kv. transmission system parture from the conventional design in that two buseswhich forms an outer belt around Chicago. The major have been provided, but there is only one oil circuitsubstations and interconnections with other companies breaker per position connecting to the two buses.are shown in Fig. 1. The main one-line diagram of the Selector switches are provided for making it possible tostation is presented in Fig. 2.Some features of the design anticipated the general

TO THE MILWAUKEE FLECTRICuse of similar equipment in other stations. The genera RAILWAY & LIGHT COMPANYdesign of the station, however, paralleled the advance of TO THE ILLINOIS NORTHERNthe art, as the station has developed from a single UTILITIES CO.ANDOTHE25,000-kw., 12,000-volt unit in 1923 to five units having OF ILLINOIS' STATION 6

a total capacity of 290,000 kw. in 1931. The fifth of WAUKEGANthese is a 115,000-kw. unit generating at 18,000 volts.Waukegan Station is unique in a number of its design

features, some of which result in a material capitalsaving, some in a greater safety to personnel, and others S.S. 88in greater operating reliability. Probably the best way NILES CENTERof presenting these features is to review the develop-

CITY LIMITSment of the station in three fairly distinct periods. (OVERHEAD TERMINAL)

S/S. III EDISTOCOMMONWEALNINITIAL INSTALLATION ELECTRSIC EDISON COMPANYJUNCTION

In the first period (units 1 and 2), a double 12-kv. bus TDISTR ICTAGERAORwas started using 15-kv. truck type oil circuit breakers DISTRICT GENERATOR

STATIONand cell-type construction to enclose the buses, dis-connecting switches, and instrument transformers, as ST.

well as the oil circuit breakers. A Cory lock system was TERMINAL)provided to prevent improper operating sequence ofthe disconnecting switches. The auxiliary equipment & LIGHT CORR & NORTOoperated at 480 volts, and an ordinary open bus was OF ILLINOIS SERVICECO.

provided for this purpose. All cables were run in con-duits from the single bus used for the turbine and

. . . _ P * . * * xIOLIET ~~~~~~~~~~~~~~~~~~CHICAGOHEIGHTSboiler-room auxiliaries. Reserve for the auxiliaries was JOLIET

provided by a tie between the unit 1 and 2 sections of FIG. 1-132-Kv. SYSTEM AND INTERCONNECTIONS OF THE PUBLICthe auxiliary bus. Feeders were run from the 480-volt SERVICE COMPANY OF NORTHERN ILLINOISauxiliary bus to VV switch groups located at variousload centers along the coal-preparation and conveyingsystem. place the oil switch on either the main or the reserve

bus, as desired. There are fourteen of these units, whichMETAL-CLAD SWITCHGEAR USED IN SECOND PERIOD range in carrying capacity from 600 to 4,000 amperes.

The second period started with the installation of a The interrupting capacity of all these switchgear unitsunit twice the size of the original one, and a radical is 1,500,000 kva.departure from conventional design was introduced by There is a number of interlocks on this switchgear

*Ele. Enr.,Publc Srvic Co of o. llinis.which prevent incorrect operation due to errors, over-Presented at the Great Lakes District M1eeting of the A.I.E.E. sights, or carelessness when switching operations are

Milwaukee, WFisconsin, Mlarch 14-:16, 1932. performed. For instance, the isolating or selector

644

32-57

September 1932 WILLIAMS: ELECTRICAL DESIGN FEATURES OF WAUKEGAN STATION 645

switches cannot be opened or closed unless the main oil has a capacity of 65,000 kilowatts, the carrying capacitycircuit breaker is open. Also, the oil circuit breakers of its metal-clad switchgear increased; the size and num-cannot be lifted from their tanks, nor can the selector ber of auxiliary motors increased because of the use ofand isolating switch tanks be lowered, when current larger auxiliaries and also because unit-type coal-pul-carrying parts are alive. verizing mills were installed. Centralized control of the

boiler coal and air supply auxiliary motors was providedAUXILIARY EQUIPMENT SIZE CAUSES OPERATING on panels similar to the one shown in Fig. 4; and the

VOLTAGE CHANGE electrical control system was designed for either manualThe use of larger turbo-generator units required or automatic operation, in response to the demands of

boilers of greater steaming capacity and larger auxiliary the automatic combustion-control equipment whichequipment. As a result of the increased size of auxil- regulates the coal and air supply for the boilers.

132 KY. LINES 33KV. LINES

I § rS l l l l 132 KV.RES BUS

I>sFI^,t I v _ ^ + ~~~~~~~~~~~~~~~~~~~~~~~~MAIN BUSRES32KV. 33S

KV. mRNRES.BBUS 3 TR SOPEN STRUCTUREA ,s TRANS.BANK 4 TRANS.BANKTRANSBANK60,01010 KA i, KVA. 60 ,000 KVA 2532 KY. TRANS. BANK S 12/132 KY. 12/33 KV. 12/33 1W.

METALCLAD 20,000 KVA.SWITCH GEAR 18/132 KV. TRANSBANK 2 E 12 KV.

60,000 KVA.12/132 KV D C

12 KV. 1 'IIItiRES.BSB_

12KV._ _ _ _ _ _ _ _ _ _

MAiN BUS 2

12 KV. METALCLAD 12 KV. CELLSWITCH GEAR STRUCTURE

I GEN. 5 __ GEN.4 __ GEN. 3 __ GEN.2 , GEN. 1115,000 KW. 65,000 KW. 50,000 KW. 35,000KW. 25,000 KW.R -/PF. -0.9 5 R F- P..0.92 P FJPF-0.35 0 R.F. -0.93iP.F-.-913KV. AUX.TRANS.26 AUX.TRANS.24 AUX.TRANS.23 AUXUTRANS.22 , AUX.TRANS.2r

AUX.TRANS.40 6,0 KA,800400 V. O KVA. 1,500 KVA. BOO0 KVA.,: 13KV./4000 KVA. 12KV./2,400 VOLTS AUX.TRANS.25 12 KV/2 400 V. 12 KV. /480 VOLTS 12KV. /480 VOLTS 12 KV./480 VOLTS

1 lK./2,400 V. 6.000 KVA.am ~~~~~~~~12KV./2,400 V.

T Ir T.-A4 ~ SWITCH HOUSE -....

AUX.AUX. 40 iZ,400V.VAUX.BUS 480 V.AUXU.BUS COAL HANDLINGTRANS.30 TRANS. 29 UNIT-2 UNIT- EQUIPMENT600 KVA. LIGHT ,v2400 KVA.-SBTTO

2,400/48OV.w Wvv-TRANS. 107 '24O00/48OV.i AUVRNW 2 IH TRANS.104AU. TRAN28AUX.TRANS5.27

c ,c 2,400/480V. BOILER ROOM 400 KVA..0-.0 'V ~~~~~240OV.AUX.BUSES~~~~2,400/480V.

-- UNIT 5-AUX. -4- UNIT 4-AUX. UNIT 3-AUX. - |2,400 VOLT-AUXILIARIES

METALCLAD SWITCH GEAR

FIG. 2-SINGLE-LINE DIAGRAM OF THE WAUKEGAN POWER STATION

Main one-line diagram of connections

iary equipment, larger motors were used; so the operat- PROTECTION ON PULVERIZED FUEL SYSTEMing voltage was changed from 480 to 2,400 volts for The use of automatic combustion-control equipmentthese motors. Also, the larger capacity of the boilersmade it necessary to provide more flexible operation of and fulverizedicoalgmade itrncsary tecisethe stoker-feed mechanism on the boilers of unit 3. To unusual care In designing the control and protective

provide.thsfeiiiy,ac rs-hftn ooswr system. By designing the system so that a negativeused Thsaranemet povids amos asmuc flxi-pressure or suction must be present inside the furnace

blity as could be obtained by the use of the customary whe it isi. evc,tepsiblt ftepleied-. otrsan cntol coal's igniting and flashing back into a pulverizing mill

and causing an explosion, are eliminated. This is theUNIT 4 DESIGN FEATURES principle followed in designing, for the boiler-feed

Although the same general electrical design was used auxiliary equipment, an electrical interlock systemfor unit 3 and 4 installations, there are a few features of which prevents any deviation from the prescribedthe unit 4 installation that are of interest. Since unit 4 operating procedure.

646 WILLIAMS: ELECTRICAL DESIGN FEATURES OF WAUKEGAN STATION Transactions A. I. E. E.

STARTING SEQUENCE by using centrifugal switches on the motor shafts to

The prescribed starting sequence of the equipment complete or open auxiliary switch circuits on the oilthat must be followed whenever a boiler is fired up is switches as the motor speed increases or decreases.as follows: UNIT 5 INSTALLATION CONSTITUTES THIRD PERIOD OF

1. Start low-speed, induced-draft fan, wound- DEVELOPMENTrotor motor. When the resistance is all out of the In the third period, the unit illustrated in Fg. 5,secondary circuit, the drum controller automati- which is over four times the capacity of the originalcally closes the high-speed squirrel-cage motor oilswitch.

2. When the induced draft fan is up to speed, theforced-draft fan oil switch can be closed.

3. After the forced-draft fan motor is up tospeed, the exhauster-fan motor can be started, andthis can be followed, in order, by the pulverizingmills and the coal feeders.

Method ofMaking Prescribed Operating Sequence Effec-tive. Each fan, exhauster, pulverizing mill, etc., has itsown oil switch, and the closing and trip circuits of theseoil switches are so interconnected that it is impossiblefor an operator to close an oil switch unless the equip-

FIG. 4-ELECTRICAL PORTION OF BOILER-CONTROL PANEL

Showing the indicating instruments In the motor circuits, the oil circuit-breaker control switches, and the motor-operated boiler inlet valves feedingthe main and auxiliary steam headers

25,000-kw. unit, was placed in service. Since thegreater part of the output of this unit is transmitted at132,000 volts, it was decided to omit the generator busand arrange for switching at the transmission voltage.This decision permitted the use of any convenient

FIG. 3-12,000-VOLT, TYPE M, METAL-CLAD SWITCHGEAR generating voltage, and the manufacturer selected18,000 volts as the most feasible from the manufactur-

ment ahead of it in the sequence is running; that is, ifan operator attempts to run a pulverizing-mill motorbefore placing the draft fans and the exhauster fan inservice, the oil circuit breaker controlling the pulveriz-ing-mill motor cannot be closed.

Two-MOTOR DRIVE FOR INDUCED-DRAFT FANS

To provide the maximum operating flexibility andreliability, two motors are used on each induced-draftfan. The fan starts on the low-speed wound rotor motor;after it is up to its maximum speed, the drum controllercompletes a circuit which closes the high-speed motor oil FIG. 5-115,000-Kw., 18,000-VOLT GENERATOR 5switch and trips out the low-speed motor oil switch.If the high-speed motor should fail to start or fail in ing standpoint. Subsequent units, of course, may gen-service, the operation of the overload relays would erate at other voltages. As the generator and its asso-function to place the low-speed motor in service. If ciated 120,000-kva. transformer bank constitute anthe low-speed motor should fail, the protective relay operating unit with no intervening bus, the generatoroperation would cause the high-speed motor oil circuit leads had to be tapped to supply the 10,000-kva.breaker to close. This arrangement, of course, compli- auxiliary transformer. The high-voltage and low-volt-cates the interlock scheme, but this problem was met age switchgear units provided for this transformer are


tripped by differential relays in case internal trouble 1. For equipment not included in the originaldevelops. In this way, interference with the operation design but which appears desirable to install later.of the generator is avoided. 2. A reduction of the investment in reserve

transformers, thus saving foundations, switchingAUXILIARY SYSTEM and control equipment, and installation costs for

The low side of this 10,000-kva., 18,000/2,400-volt an "unproductive" transformer.transformer is connected to the main 2,400-volt station 3. The excess capacity required for stationauxiliary bus. This bus can be sectionalized by units overloads.if desired, or it can be operated as one bus. Reactors The general arrangement, design, and type of auxil-have been provided between sections of the auxiliary iary switchgear used for units 1 and 2 and for the suc-bus for fault current control. Power for starting the ceeding three units offers quite a contrast, as well asauxiliaries on units 3, 4, or 5, or for emergency operation showing the development of the art. The auxiliary sys-

FROM UNIT-S FROM UNIT-4 FROM UNIT-318 KV.SW. GEAR 12 KV.-SW. GEAR TRANSFORMER 25 12 KV-SW. GEAR

TRANSFORMER 40 V.,TRANSFORMER 26 K6000 KVA. TRANSFORMER 2410,000 KVA,.VW 6,000 KVA. 62,000120OT 4,000 KVA.

18,000/2400 VOLTS "'2,000/2400 VOLTS 2 004 V12,000/2400 VOLTS2400 VOLTAUX.BUS UNIT-5 UNIT-4 UNIT-3

IN SWITCH HOUSE it E T _ i

6 35 2 4 7 35 22 4 8 62 34 5 6 13 46 2 22544 3 3 7 9

AAiTRANSFORMER 30 TRANSFORMER 29 TRANSFORMER 27600 KVA. w 400 KVA. 400 ISVA. 400 KVA.

2400/480 VOLTS 2400/480 VOLTS 2,400/480 2,400/480 VOLTSVOLTS

2,400 VOLT UNIT-4AUXBUSESIN IT-5 UNIT-3BOILER -ROOM I _________

I 10 11 121312131213 1I 11 121312 1312 13 1I 11 12 1312 1312 131 13 12 1312 1312 11 1014 141312 131211 10 1312 1312 11 I10 1I 1I 11 11 1I 11 11 1I 11 11BOILER-16 AUXILIARIES 1BOILER-15 AUXILIARIES BOILER-14 AUXILIARIES BOILER-13 AUXLIARIES BOILER-12 - BOILER-I1l L BOILERS-ID & 9 BOILERS-8 & 7J

AUXILIARIES AUXILIARIES | AUXILIARIES AUXILIARIESFROM 12KV.OIL

| l FROM 12 KV.OIL CIRCUIT BREAKERS CIRCUIT BREAKERUNIT-5UNIT-4 UNIT-3 ~~~~~~~~~~~~~TRANSFORMER 23 AAkATRANSFORMER 21 TRANSFORMER 22 JVX'4UNIT-5 | UNIT-4 UNIT-3 1800 KVA. ' 1800 KVA. 1500 KVA.

480 VOLT 480 VOLT UNIT-2 UNIT- X

COAL HANDLING

NOTE:- ONLY BUS POTENTIAL TRANSFORMERS ARE SHOWN EQUIPMENT_____________________ZSUBSTATION

/ DISTRIBUTIONR soI 1, UNITS-3,4 AND 5 UNITS-3,4 AND 5 UNITS-3,4 AND 5 UNITS-I AND2DISATRIBTIG SWITCH HOUSE 2,400 VOLT BOILER ROOM 2A00 VOLT 480 VOLT AUXILIARY 480 VOLT AUXILIARY MOTORS MOTOR

1SWITCH GROUPS 1 1 AUXILIARY MOTORS AUXILIARY MOTORS DISTRIBUTION GROUPS AND DISTRIB. GROUPS SYMBOLSI GENERATOR AIR FAN 101 NDUCED DRAFT FAN 5ISPARE SWITCH GEAR UNIT 23 DISTRIBUTION GROUP I2I OILER FEED PUMP IFORCED DRAFT FAN 16 BOILER ROOM DISTRIB.GROUP 241 FORCED DRAFT FAN o WOUND ROTOR

1. MILL FEEDER MILL FEEDER MILL FEEDER U3CIRCULAT. WATER PUMP |12EXHAUSTER 17 BOILER ROOM EMERG.FEED 251 INDUCE0DRAFT FAN ICONTROLLERMILL FEEDER IMILL FEEDER1 SMILL FEEDER I4'CONDENSATE PUMP 13 PULVERIZING MILL 181TURB.ROOM DISTRIB.GROUP 261 CIRCULATINGWATER PUMP CTLMOTOR ACTUATOR MOTOR 5 SERVICE PUMP 141ASH SLUDGE PUMP 19 CRIB HOUSEDISTRIB.GROUP 27 BOILERI FEEDPUMP ROTOR WITH

(BRUSH SHIFT) MOTOR 6 ASH SLUICE PUMP -20 SWITCH HOUISE DISTRIB.GROUP 28 SERVICE PUMP DOUBLE'TYPICAL CONNECTIONS OF FEEDER MOTORS 7 QLGHT TRANS.WITH V.REG.|21 MOTORGEN SETBATTERY CH 29 CONDENSATE PUMP WINDING

8 MULE HAUL MOTOR 22 TURB.ROOM CRANE MOTORS 30DBOOSTER PUMP IR I19 SPARE SW. GEAR UNIT 31 LIGHTINGTRANSFORMER )SCARGRE II ______________ ___1__I__I_I_ 321 SPARE SWITCH GEAR UNIT CAG

FIG. 6-SINGLE-LINE DIAGRAM OF THE STATION AUXILIARY SYSTEM OF WAIJKEGAN POWER STATION

in case one of the station auxiliary transformers is out tem used for units 1 and 2 was of an open-bus type withof service, is obtained from the station auxiliary bus. its connections extending from the oil switches up to theFig. 6 gives a one-line diagram of the station auxiliary disconnecting switches and then to the overhead bus,system. and considerable space was occupied for a compara-The present auxiliary power installation provides tively small number of pieces of auxiliary equipment.

9.4 per cent of the generator capacity in auxiliary trans- All of the switching equipment for the turbine and theformers. The active and reserve transformer capacities boiler-room was supplied from a single bus in the switch-are 7.4 per cent and 2 per cent respectively. These house. On the other hand, for units 3, 4, and 5, 2,400-transformer capacities have been selected so that we volt metal-clad switchgear has been used for the mainhave 20 to 30 per cent unused capacity in each trans- -auxiliaries, and separate buses have been provided forformer under normal demand conditions. This nor- the equipment in the turbine-room and in the boiler-mallyunusedcapacityprovides: room. Two feeders are provided from the main bus


over to the boiler-room auxiliary bus. These feeders kva. transformer bank, in fiber ducts. This 16-ductare protected differentially, and the bus in the boiler- bank was designed in the form of a square surroundingroom, as well as the main bus in the switch-house base- a large, square tile placed in the center of the duct bankment, can be sectionalized. to permit air circulation thus equalizing the internal

and external temperatures of the ducts.GENERATOR FIELD CONTROL Special care in design was used to make the cables

Another point in which the change in practise is carry equal load currents and to avoid injurious sheathapparent is in the method of controlling the generator voltages. The cable phases in the duct have been sofield. Instead of using generator field rheostats, as had arranged that the electromagnetic fields surrounding thebeen done for the preceding four units, a main and a cables tend to neutralize each other, thus equalizingpilot exciter have been provided on the shaft of genera- reactances and avoiding reductions in carrying capacity.tor 5. The exciters and the generator field are so inter- As it was considered more economical to have in-connected that variations of the main exciter field duced voltages on the cable sheaths than to suffer therheostat provide the means of controlling the generator losses due to induced sheath currents, cable-sheathvoltage. This arrangement results in a considerable insulators were placed at the ends and at about thesaving due to the fact that there are no generator field midpoint of the 550-ft. fiber-duct run, thus dividing therheostat losses; in addition, a much more rapid and cable sheaths into two sections. These two cable-sheathflexible method of controlling the generator is provided. sections are grounded at their midpoints, thus makingIn case automatic voltage control is considered advis- the induced sheath voltage too small to affect the lead-able, this feature can very easily be provided at a com- cable sheaths injuriously.paratively small additional cost. On the other generator installations, short cable runs

Excitation. All the generator field exciters, except on have been installed between the generators and the oilunit 5, are connected to a common excitation bus. As all circuit breakers connecting to the 12-kv. station bus.these exciters have excess capacity, this design provides On unit 4, for instance, this run is installed mainly in thereserve for any of the exciters on the first four generators. open air in split aluminum tubing suspended from theConsideration of the facts, however, that generator 5 turbine-room floor. Since conditions were somewhatmust be stopped to repair either exciter, because of their different for the preceding three units, an ordinary fiber-locations; that the main exciter will operate self- duct and concrete cable run was used.excited, thus making it possible to operate without the As an added safety factor, 17,000-volt insulation onpilot exciter, and also the reliability of present day the cable has been used for the units which operate atexciters, led to the conclusion that the expense of re- 12,000 volts between phases, or 6,900 volts to ground.serve excitation was unjustified. On unit 5, which operates at 18,000 volts or approxi-

Instrument Transformers. One of the features of the mately 11,000 volts to ground, 25-kv. insulation hasgenerator installation for which it has always been been provided on the cable. Not only has higher insu-rather awkward to make a satisfactory design is the lation than required for rated voltage been used, butinstrument-transformer installation for metering and very liberal conductor areas have been provided also.protective purposes. On the first four units installed, On all the 12,000-volt cables, compound-filled potheadsthe current and potential transformers have been in- were used. On the 18,000-volt unit 5 installation, oil-stalled in the generator foundations in rather inacces- filled potheads, as well as oil-filled joints, have beensible places, or in rather unsightly and inaccessible used as an added safety factor which should insuretransite enclosures on the side of the generator founda- maximum reliability in service.tions. On the unit 5 installation, however, an extension Small Power Cable. As a result of the development ofof the metal-clad switchgear idea was made. The various types of armored cable which have proved quitemetering and protective transformers were placed in satisfactory in service, it has been possible to eliminatemetal-clad petrolatum-filled compartments in a recess the very expensive conduit runs which were needed toin the side of the generator foundation in such a way as protect cable of the ordinary type from mechanicalto make a safe, compact, accessible, and well-appearing injury. Instead, troughs suspended from the ceilinginstallation. The metal-clad instrument-transformer are provided. The armored cables are laid in thesecompartments were designed with potheads on the troughs much more quickly than cable could be pulledlower side ready for the installation of the generator through conduit. As a result of this change in practise,cables. the cost of our cable installations has been materially

reduced because of the saving in drafting-room andGENERATOR CABLE AND POTHEAD INSTALLATIONS AND field work.

INSULATION

On the unit 5 installation four single-conductor, PROTECTIVE RELAYS3,000,000-circular mul, paper-core, 25-ky. .paper-insu- Various types of relays have been used to protect tnelated, lead-covered cables are used for each phase. -equipment. The generators, cables, and transformersThese cables extend from the generator tOr the 120,000- are protected with differential relays. The transformers


are also equipped with overcurrent-relay protection. type steel structure. These two double bus switchgearSome of the motors are equipped with phase-balancing units are arranged as indicated in Fig. 8, and consistrelay protection and others with overcurrent protec- of oil-filled cable buses and interconnections, specialtion, depending on the particular duty. The 132-kv. motor-driven disconnecting switches enclosed in metalline protection consists of impedance relays which oper- housings, oil switches equipped with potheads insteadate in conjunction with overcurrent and undervoltage of outdoor bushings, and special bus connections andauxiliary relays. This arrangement makes it unneces- disconnecting devices for the instrument transformers.sary to change current-transformer ratios in light or As this switchgear is the first of its kind, the detailsheavy-load periods. of its capacity and design features are of interest. The

switchgear is rated to carry 1,200 amperes and the oilOUTDOOR INSTALLATIONS circuit breakers will interrupt 2,500,000-kva. at rated

The outdoor installations at Waukegan have gone voltage. The capacity of the buses may be increasedthrough two successive stages of design similar to those to 2,400 amperes by installing another set of buses.involving the indoor equipment. At the time unit 1 was The present buses consist of 3,020,000-cir. mil., oil-installed, it supplied a 25,000-kva. 12/33-kv. trans- filled, paper-insulated, lead-covered, copper-armoredformer bank, and an open-type main and transfer-bus cable. Isolated racks support the bus cable about nineswitching structure. At this time, also, the first feet above the switchgear foundations as it loops from132,000-volt installation was made. This consisted of switchgear unit to switchgear unit. The ends of eacha 30,000-kva. water-cooled transformer bank provided of these bus cable loops are insulated, and the midpointwith an air-break switch only, on the high-voltage side. of each cable sheath in each loop is grounded to keepThe associated transmission line extended about 28 the induced voltage in the cable sheath at a minimum.miles to a step-down substation.The second stage occurred in 1927 as a result of the

installation of the second 132-kv. line. This necessitated

the 132-ky. switching structure and bus, which wasIinstalled in conjunction with this unit. At this time, a

60,000-kva. water-cooled transformer equipped withload-ratio control was installed. The steel switchingstructure was added to as additional lines were needed,and for unit 4, a 60,000-kva. oil air-cooled transformerbank was installed. This bank is also equipped withload-ratio control equipment.

132-Kv. SWITCHING STRUCTUREThe 132,000-volt structure has a number of rather

unusual features. To conserve space in a north-and-south direction, it was necessary to use more in aneast-and-west direction. This permitted placirrg the The disconnecting switch consists of contacts in anequipment for a line and a transformer in a bay 38 ft. oil-filled tank equipped with entrance bushings which6 in. long from north to south, but much wider than are, in turn, enclosed in an outer housing. The tank,thisfromeasttowest. Asthemainbusislocatedabove as well as the bushing on the bus side, is raised andthe other equipment in the middle of the structure, the lowered by a motor-driven mechanism, and overtravelstructure appears to have three buses. The line and is prevented by limit switches. When the tank istransformer buses, however, are connected so that they lowered, the circuit is opened under oil and the busform a rectangular "ring" bus with the main bus in the contact on the entrance bushing withdraws from its busmiddle. The line and transformer or reserve bus may receptacle, thus providing a visual separation, whichbe sectionalized by means of an oil switch, or by means may be observed from the outside of the housingof load-break disconnecting switches. through a sight glass. The bus receptacle consists of a

hollow porcelain shell that forms a part of the main132-~Kv. METAL-CLAD SWITCHGEAR structure into which the entrance bushing on the dis-The first 132,000-volt switchgear ever used has been connecting switch tank enters. The opening in the

placed in service as part of the unit 5 installation. Two lower end of this porcelain shell is automatically covereddouble bus units were installed as shown in Fig. 7, one by a metal cover when the disconnecting switch is with-for switching the high-voltage side of the 120,000-kva drawn. These switches are operated in groups from thetransformer bank supplied by generator 5, and one oil circuit breaker control panel, or individually at thefor an additional 132,000-volt transmission line. The disconnecting unit.buses of these two units are connected to, and form an As it is seldom necessary to disconnect a potentialextension of, the main and reserve buses in the open- transformer, this disconnecting device is not motor


operated. A portable motor has been provided, how- closed. An interlock also prevents operating any of theever, for raising or lowering the potential transformer line disconnecting switches unless the line cable test"coupler" tank whenever necessary. switches are open. Conversely, no line cable test switch

132-Kv. Switchgear Safety Features. There is a num- can be operated until line disconnecting switches haveber of interlocks provided to prevent operating errors been opened. An interlock also prevents the lowering ofand to protect personnel. For instance, one of the inter- any potential transformer coupler tank unless thelocks prevents opening the upper door in the discon- ground switch and test switch on that phase are closed.necting switch house until the disconnecting switch is An interlock prevents opening any ground switch or

LINEDISCONNECTING TEST

POTENTIAL COUPLER SU UBUS OIL TRANSFORMER OIL ATEST

TEST - CURRENT SWITCH USTUDSTUD SWITCH ~~~~~~~~~~~~TRANSFORMER

US DISCONNECTING DISCONNECTING DISCONNECTING DISCONNECTINGBS WITCH SWITCH SWITCH SWITCH BUS

ONE LINE DIAGRAM

BUS CABLES ~~~~~~~~~~~DISCONNECTING END BELL BUS CABLES16-2

TEST AND TEST AND~~~OTNTIL~ONDAN

GRUDSWITCH GROUND SWITCHANFOMR WIC OLSWTC WIC

POLE~ ~ OI RS R ESER OI

OPERATEDS SICGROUND E 1T

SWITCH SUD IINSPECTION

7 FOR>OPERATING ID I°

iR. SEC....0T.IO TJR .5,,

DC GDISCONNECTI N E REV T DISONNSWIT FG 8WITCH OI TH 132 K E - D TG

G'11-6XL 17-7' 21L 84,1 1125 Io'8-7 1 16XI SECTION THRUELVTOFIG. 8-LAYOUT OF THE 132-KV. METAL,-CLAD SWITCHGEAR

Showing a plan and elevation, the internal features of the disconnecting switches, and a one-line diagram of connections which conforms to thephysical arrangement of the equipment

opened, which causes the shutter preventing access to test switch until the potential transformer coupler tanklive parts to close. Another interlock prevents opera- is in the connected position. This is accomplished bytion of any or all disconnecting switches on both sides of means of a system of Cory locks.the breaker unless the breaker is open. This interlock AC A.ML RVis effective on each disconnecting switch on individualA-.CRML DIVoperation, as well as on group control. The breaker One of the recent additions to the coal-handling sys-cannot be closed unless all the disconnecting switches tem at this station is the coal-car mule, which pushes theon both sides of the breaker are fully open or completely loaded cars up an incline to the rotary car dumper. The


special service requirements of the car-mule drive would another limit switch operates to energize a contactornormally dictate the use of d-c. motors, but, as direct which accelerates the main motor. This process con-current has not been necessary for the other auxiliaries, tinues in six steps until the main motor reaches itsexcept for control purposes, it was decided to avoid its maximum speed of about 300 ft. per minute. As the caruse for this device, if possible. Accordingly an a-c. sys- approaches the car-dumper cradle, the car is slowedtem was developed which is, perhaps, the first of its type down to 150 ft. per minute by inserting automatically allused in this country. Solution of the problems of se- of the main motor resistance, and the torque motor iscuring large variations in torque with large variations in put on its high-speed winding. If the cradle is properlyspeed, of obtaining a flexible control system, and of seated, the car and mule will proceed to the final muletaking the slack out of the hoisting cable to prevent limit; at this point the motors stop automatically andbreakage when the load is suddenly applied, have made the brakes set. By reversal of the master switch thethe use of a-c. motors possible. motors operating the track gates, through which theThe essential feature of this installation is the use of a car mule leaves or enters the pit, change the position of

slow, two-speed, 440-volt, high-torque motor. Coupled the gates and the car mule is lowered automatically.directly to the torque motor is the 500-hp., 2,300-volt,wound-rotor, main driving motor. The drive shaft to .c s

which the motors are coupled is geared to the car-mule Discussioncable-hoisting and lowering drum. A. H. Lovell: To one who is not a resident of this territoryThe control system of the equipment which pushes a of Chicago and its adjacent western surroundings, it is very

loaded coal caruptheincline is complpuzzling that Waukegan, built for heavy energy production, inloaded coal car up the incline is complex, but to hoist a relation to the Chicago load, should have chosen units of onlycar automatically, it is only necessary for the operator to 25,000 kw. in 1923 and 65,000 kw. in 1930. Will the authormove a master control switch to the final point. This discuss this in relation to the size of the load in Chicago atcloses contactors which put the torque motor on its those times?high-speed winding and thus bring the car mule out of W. S. Monroe: The history of the Waukegan power station

the pit at a speed offt. perminute.Asthecarfrom the time the first unit was ordered in 1921, represented, inthe pit at a speed of 150 ft. per minute. AS thRe car a large measure, the development of the power station industrymule approaches the coal-car which has rolled over the in the Chicago District so far as steam pressure and steamhump, a limit switch operates and energizes inter- temperature are concerned, and the change of boiler furnacesmediate circuits that put the torque motor on its low- from the chain grate stoker to pulverized coal. Referring to thespeed winding, so that the mule engages the coal-car size of the units, the first two represented the largest units that

it seemed desirable to put into the station, considering the loadat a speed of 50 ft. per minute. This operation also available in the distrct, and the last three units, Nos. 3, 4 a:6d 5,places the main motor on the line with all its starting of 60,000, 75,000 8id, 105,000 kw. respectively, were each theresistance inserted. After the car has been picked up, largest single shaft unit available at the time they were ordered.

electrical design features of waukegan station

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