25/41-MW Cyclic Steam Power Plant ServingHot Strip Steel Finishing MillD. V. Fawcett, Senior Member IEEE

Abstract: The 6-stand hot strip finishing mill planned by utility system. Accordingly, Algoma Steel decided toAlgoma Steel would impose frequent swings on the utility tie install a steam power plant to serve the cyclic load of the sixline of 41 MW and 41 Mvar. Each swing would occur over a finishing stands. The arrangement chosen was to operate10-second interval. To avoid these swings on the utility tie,a steam power plant rated 25 MW continuous with features two Algoma turbine-generators in parallel with the electricpermitting peak cyclic loading to 41 MW and 41 Mvar was utility and to vary the megawatt and megavar output of theinstalled. Special megawatt and megavar controls vary the Algoma generators so as to match the varying input to thepower plaint output to match the varying input to the strip mill. finishing stands.High-speed recordings of plant performance during strip milloperation are included. This is believed to be one of the few,if not the only, steam power plants operating in this manner. Supply of the Steam Power Plant

In April 1961, a turnkey contract for engineering, pro-ln late 1960, The Algoma Steel Corporation, Ltd., Sault curement, and installation of the steam power plant wasSte. Marie, Out., Canada, decided to add a 106-inch-wide awarded to Canadian Westinghouse Company Ltd. Ashot strip finishing mill to their plant. An existing reversing a part of the Westinghouse turnkey contract, major sub-mill was available to serve for "roughing," i.e., reducing steel contracts were awarded as follows:slabs to approximately a 1-inch thickness suitable for "finish-

ing." Th.iihn ilwudte euetetik 1. Steam generator and auxiliaries: Babcock-Wilcox anding." The finishing mill would then reduce the thick- Goldie-McCulloch Ltd., Galt, Ont., Canada.ness to the desired size and produce steel strip in specified 2. Controls for steam generator: Bailey Meter Company Ltd.,widths up to 106 inches. Montreal, Que., Canada.A 6-stand tandem continuous mill was selected with a,

6000-hp dc motor on each of the first five stands and a 5000- 3. Foundation and building design: Foundation of CanadaEngineering Corporation Ltd., Toronto, Ont., Canada.hp dc motor on the last (sixth) stand. A transformer andrectifier unit arrangement was chosen to serve each stand Algoma Steel directly handled contracts to l)rovide a newmotor from the Algoma plant 11-kV ae distribution sys- pumphouse to supply cooling water to the power planttem. and the finishing mill. The power plant and pumphouse wereThe maximum stand loading for the various planned placed in service in August 1963, at the same time as the

rolling schedules was approximately 7 MW for each of the startup of the strip finishing mill.first five stands and 6 MW for the sixth stand, a maximum The basic power plant consists of one steam generatortotal of 41 MW. This load would build up in six steps over a serving two identical condensing turbine-generators and has10-second interval as the steel progressed from entering the a 25-MW continuous rating with short-duration peak-first stand to being simultaneously in all six stands. The ing capability up to 41 MW.41-MW peak would last for about 7 seconds, and the steel Figure 1 is a single line electrical diagram of the power plant,would then leave the first stand. The load would reduce cooling water pumphouse, strip finishing mill, and con-in six steps over the next 10 seconds as the steel successively nections to the utility 115-kV system. Most of the featuresleft the stands. During the following 95 seconds, there of the power plant are primarily conventional; these will bewould be no steel in the finishing mill and its power require- diseussed later in the paper.ment would only be that to keep the drives rotating at thedesired speed. At this point, another bar would enter the Special Megawatt and Megavar Controlsfirst stand and the load cycle would repeat. Bars wouldtherefore enter the mill every 123 seconds for this particular Figure 2 shows thesplecial ontrol system arrangementrolling schedule, which requires maximum stand loading. for matehing power plant megawatt output to the megawattWith rectifier power supply arrangement, the operating input to the finishing stands. The sdecial eontrols (A

power factor is about 0.71. Therefore, the megavar cyclic and B in Fig. 2) are of the transistorized amplifier type.loading would also peak at about 41 Mvar. Each transducer (C in Fig. 2) consists of a torque motorThe utility generation in the area totaled 175 MW and which positions a cup valve in response to the value of

consisted of several hydraulic plants, each with a capacity of a de milliampere signal it receives from the special control20-40 MW. A 115-kV tie existed between this local gen- B. The variable position of the cul) valve establishes a vari-eration and the much larger system in southern Ontario. able control oil pressure. This variable oil pressure deter-

Studies indicated that this cyclic loading, with peaks of mines the opening of the governor valves and, hence, steam41 MW and 41 Mvar, was too severe to impose up)on the flow to the turbine. This, in tuarn, varies the generated

megawatts. Less than 1 second is required for the psowerplant output to change to match a new value of inpout to the

Paper 31 TP 65-36, recommended and approved by the Power strip) mill. A/ 2-conductor coa.xial cable transmits a dc signalGeneration Committee of the IEEE Power Group for presentation over the one-half mile from the stril) mill to the power l)lant.at the IEEEX Winter Power Meeting, New York, N. Y., January 31- (from controls A4 to B).February 5, 1965. Manuscript submitted June 29, 1964; made Sicthrisa12eonitrvlbwennryf eavailable for printing December 14, 1964. Sneteei --eoditra ewe nr fthD. V. FAWCETT is wit,h Canadian VWestinghouse Company Ltd., steel into adjacent stands and the power l)lant resposnseHamilton, Ont., Canada. iS less than 1 second, the meg;awatt requirement from the

APRIL 1965 Fawcett-25/41-MW Cyclic Steam Power Plant 32?'

115KV FROM UTILITY 11 KV BUS AT MAIN SUB

CONNECTIONI~~~~~~~~~~~~~~~~~f. MILE | THROUGH

MIVA SL MIVAXMVAXiT OCAXABE| | TO ELECTRIC

FROM BOILER ~~~~TIIT

MAIN SUBSTATION II411KV POWER FOR MAINl[T} m [ ~~~~~~~~~~~~~~~~~~~~STANDS OF 106in. + 1KREACTOR TIE BUS TITO=

l ~~~~~40MVA TRANSF.

;Ii KV POWER PLANT S0 OIGNL TO

)

_TT I ~~~ __ SWiTCHING STATIONS -~33L-c 610 psig STEAM >MVA'7 15 625 MVA EACH FROM BOILER

1575V ril ril Fig. 2. Block diagram of special megawatt control system forNO.) ) ) ) 106 in. STRIP FINISHING MILL 11KV power plant

NO)AU | [ [ A-Special control at strip mill to transduce megawatt load to dc

250 HP MOTORS L L L L L 1 L L L signalG3

5G4TEXCITET T 7S B-Special control at power plant transmits dc signals to loadT575V 2-4KV the turbine-generators to match strip mill loadAUX AUX C-Special transducers: dc milliamperes to oil control pressure

STRIP FINISHING MAIN STANDS 5V5V

I7soL50 $) t) AuxAUX D-Standard turbine oil control system working into governor

KVA 625 KW EACH [v

control matches the power plant megavar output to the mega-var input to the six finishing stands.

1_ 2 MVA EACHl LWhen the strip mill is not rolling, the power plant operatesin a conventional manner under standard governor and volt-

n fn ~~COOLI NG WATER2-4 K V PUMPHOUSE FOR age regulator control. In the event that the tie to the

ATURBNE GENS. 3, utility is lost, the strip mill is automatically tripped and theT T T TFINISHING MILL 25-MW continuous capability of the power plant is auto-

matically brought into service. This, in conjunction with

Fig. 1. Single line of power plant, water pumphouse, strip high-speed underfrequency load shedding, has helped onfinishing mill, and connections to utility; various other mills several occasions to maintain important plant loads.are served from main substation breakers (11-kV tie to another Computer Studies

115-11-kV 40 MVA substation is also shown)A modified stability study of the expected transient power

flows was performed in 1961, by Westinghouse in Pittsburgh,

electric utility is limited to approximately the requirement on an IBM 7090 digital computer. This study confirmed thatof one stand for a duration of less than 1 second. This re- the Algoma generators would remain in step with the utilityquirement occurs each time the steel enters a stand. Sim- when subjected to the 41-MW peak rolling schedule.ilarly each time the steel leaves a stand, there is a mega-

To aid in the design of the megawatt matching controliarly, eachd ti the steel avesiatand ere is a mega- system, analog computer studies were made in 1962, by

watt feed troppedbytheutliy approximately equi valth meg- Westinghouse Electric Corporation, Pittsburgh, Pa. Severalwatt load dropped by the stand and for an interval of less difrn coto sytm wer inetgtd n h njtha secnd different control systems were investigated, and the onethan 1 second.To maintain stable boiler combustion on this cyclic load- selected was then designed.

ing and desired minimum turbine loading, a minimum baseload of approximately 6 MW is generated at all times. Steam Power Plant Peaking Capability Based on StripSince this is the peak requirement of the sixth finishing Mill Requirementsstand, it was convenient to exclude the sixth stand from the The ability of the 25-MW steam power p)lant to delivermegawatt matching control. Therefore, the megawatt up to 41 MW for short durations is obtained by using tworequirement of the sixth stand is furnished by the utility. 12.5-MW rms rated turbine-generators that are each me-For the 41-MW peak of the finishing mill, the power plant chanically capable of producing 20.5 MW. As the turbinegenerates base load plus the megawatt input to stands 1 steam valves open to take a total steam flow from the boilerthrough 5=6+(41-6)=41 MW, and the utility furnishes in excess of that corresponding to 25 MW, the boiler drum6 MW to stand 6. pressure falls below the nominal 610 psi. This permitsThe control system for megavar matching utilizes a stand- more steam to form from flashing in the drum. The steam

ard control cable pair with low level alternating current for pressure continues to drop for the duration of the intervalsignal transmission from the strip mill to power plant. This in which the steel remains in the finishing stands. Thesignal operates into special megavar comparitors which were steam recovers to 610 psi after the steel leaves the mill andpart of the otherwise standard-type WMA high-speed mag- before the next bar enters the mzill.netic amplifier generator excitation regulators. This megavar For each bar, the energy requirement which is in excess

328 Fawcett-25/41-MW Cyclic Steam Power Plant APRIL 1965

of 25 MW is obtained by permitting the steam pressure to BAR 31 STARTdrop and flashing additional steam in the boiler drum. The 24l-drum is correspondingly oversized. The turbines are I Ik1X1j 18[_ - 12designed to produce 20.5 MW each at any steam pressure EI MW TG3 L 6between 610 and 400 psi. o

Special controls were supplied for the steam generatorto maintain stable performance on this cyclic loading and 128MVARto increase the firing rate during the peak loading to en- MVAR TG. 12sure recovery of the steam pressure to 610 psi as soon as possi- 6

0ble after the steel leaves the mill.The 41-MW peak which has been previously mentioned _ - 24 MVAR

is the maximum stand loading of the various planned roll- - l_18ing schedules. There are, of course, many other rolling MVAR TG44 2

schedules of varying power requirements, as determined by v_ ._the thickness and width of steel strip being rolled.The rolling schedule which requires the maximum energy _ 24MW

18had a peak requirement of only 32 MW. The load build- 12up takes 10 seconds, is maintained at 32 MW for the next S4 MW TG4 674 seconds, and then drops off in the following 10 seconds. 88 80 72 64 56 48 40 32 24 16 8 00The time until the next bar is 176 seconds. Bars would TIME IN SECONDStherefore enter the finishing mill every 270 seconds. Thisis the schedule which produces the maximum steam pressure Fig. 3. Megawatt and megavar output of turbine-generatorsdrop and which, therefore, determined the boiler drum size andthe turbine minimum steam pressure and maximum steamflow requirements.

Operating experience has shown that the steam pressure BAR 61 STARTdrop is not as great as anticipated. For maximum energy -_ ___ _X_r 24 MWloading from the strip mill, the steam pressure on occasion I 18drops to 450 psi but generally not below 470 psi. _ 2To ensure adequate recovery of steam pressure before enter- MW TG3 6

ing steel in the mill, and to develop the strip mill operator'sappreciation of this requirement, a steam pressure gauge MW FROM UTILITY SYSTEMand steam pressure interlocking relay are mounted in the A MWstrip mill operator's pulpit. The gauge and relay are elec- MW TO UTILITY SYSTEM 10trically operated from a steam pressure transducer locatedat the power plant. | | = 17 1 30MWThe author is not aware of any other steam power plant in 10

which the turbine-generators and steam generator have L.4 0been designed and operated to produce peak outputs that FINISHING STANDS THROUG 5

are considerably in excess of their continuous capabilities. - 24 MVARIn this installation, the peaking capability is 41/25 MWX 7lK 1 - 12100=164 per cent of the continuous capability. MVAR TG3 6

0

Testing and Performance on Cyclic Loading 56 48 40 32 24 16 8 0TIME IN SECONDS

Considerable testing of the steam generator and turbine-generators on cyclic loading was performed in Julv 1963, Fig. 4. TG3 megawatt and megavar, utility megawatt, mega-

1 ~~~~~~~~~wattinput to stands 1 through 5, for bar 61to ensure that the power plant would not cause delay ofthe scheduled August 15 startup of the strip finishing mill.This was accomplished by feeding artificial varying de-mands for megawatt and megavar into the special elec- ties obtained from transducers of the Hall generator type.trical controls using manually operated rheostats and step- Figure 3 shows the megawatt and megavar output ofping switches. each turbine-generator for the rolling of bar 31 of the 103The first steel was rolled quite successfully on August scheduled bars. These two turbine-generators are d?sig-

15. During the next two weeks, high-speed recordings were nated as TG3 and TG4. Even though TG3 and TG4taken of the power )lant response to the cyclic loading of the and their controls are identical, it is significant to note howStr'ip mill. closely their outputs match.

It was then decided to return at a later date and repeat Figure 4 shows the megawatt and megavar output of TG3the recordings to determine if any change in performnance had for the rolling of bar 61. Also shown is the megawattoccurred. High-speed recordings were taken again on input to the strip finishing stands 1 through 5. The powerMarch 4, 1964, during the scheduled rolling of 103 bars. plant is intended to change its output to match the inputThese showed that the performance had not changed since that to stands 1 through 5. Any mzismatch is recorded as "mega-at startup in Augulst 1963. Some of these recordings are watt flow to or from the utility."shown in Figs. 3-5. Figure 5 shows the megawatt output of TG3 and TG4The recorder was an Offner. All external connec- for bar 97. Also shown are the megawatt input to stands

tions were made with shielded cable and carried dc quanti- 1 throulgh 5 and the megawatt mismatch.

APRIL 1965 -Fawcett 25/41-MW Cyclic Steam Power Plant 329

BAR 97 START

18 MW

MW TG3 6 4

10 HEADERLAAAIAJ I MIW FROM UTILITY SYSTEM MW PSIG fOMW

M Ah r w-1MWMW TG4TLTSSE 0 UBN

TIMEINSECONDS mCOTRO

Fig. 5. TG3 and TG4 megawatt, utility megawatt, megawatt tostands ~1 hogh5 orbr9 Fig. 7. Steam header pressure and temperature and turbine

governor control oil pressure during strip mill operation,March 4, 1964

3 1\ POWER PLANT BUS KV _112 r L. .-\ '1 A X A

20 MVARTOANDFROMUTILITYSYSTM, 1 ; P40 \ ~ ~MWINPUT TO STRIP NO\StCegwtAadLt - , ,/

0~~~~~~~~~~~~~~~~~~~~~~~~~

0~~~~~~~~~~~~~~

40 MVARINPUT TO STRIP~1 STE

30 FINISHING STANDS 1 THROUGH6NDS20 and megaw, u y mawattadmegawar

o / 51 1 / iJtostands1 through Fig.rba 97gov ilerconroloiwatessrleel during,19 strip mill opneratin

° ' 1 "' / i; 6, for bars 92 and tionMrch4 196BAR POWE PLANTBUS KV t9

10

20

Figre shws uanites ake frm Fig.we plantcn 02^

Tabl I ive Iaao h eo h burs kieovolts utoil-1

40 MW'RTOANPU TO STIPSFINISHNTG SANDSF 1UTH GIY and

10 tough

01 6,/X3/X5 for4X.0 barsXOO692 an tion\ \

BAR93 NPBAR 92 93RI

Figure6shows1 qantieroutienstknfom thepowder plant on-te Fg9 olrtaadiflwMrh,94srpilpr

oileronSo rcoardSaTer theywer e swio st sped S aMFo

steelrin therfinishin mill. pml rligpeidonNac

Figs. F3-6. 6 Power plant

TableDS

6154/0'/x5 itys.5 megawatt.and9,30 50ega/Xvar5s/X1.O mega0.7

97 50aXtXt1and/21megavars0047Fiue 71 rerpodcinso teore charts ontheog Fig.89. Boilerdstemwadaierleflo,March 4, 1964, strip mill opera

bole coto6oad hseso h wide swins whichdation

occurred throuhowquatithesstripnmilrolling poerio olntMarch

43(whncthes recrdmingsein Figs.e36wrtakplen).th olig330barsw92ta-d5931aMd CyclictSteambePower PlanttAPRILw196n

PRESSURE and two condensing turbine-generators, each rated 12.5/20.5 MW. The building fully encloses all equipment.The basement of the boiler bay includes the draft fans,

pulverizers and primary air fans, and boiler feed pumps.The basement of the turbine bay contains the condensate

FLOWL w hL = | pumps, vacuum priming and main ejectors, oil reservoirs,B/H _ | # a Xmotor driven main exciters, and generator terminal cu-

bicles.' > ^ _ :/ X /nb| The switchgear room contains the 11-kV and 575-volt

_; /4/4' X | switchgear, 575-volt motor control center, auxiliary trans-,as D /9/0formers, battery and dc controls, excitation regulators and

field breakers, and special turbine governor electrical con-trols.Two adjacent control rooms are located above the switch-

gear room. One houses new controls for the four originalTEMP boilers and the new boiler. The other room contains the

generator controls, and also a telemetering and super-Fig. 10. Boiler feedwater flow, pressure, and temperature, visory control board purchased by Algoma Steel for use

March 4, 1964, strip mill operation with their revamped 11-kV ac plant distribution system. Aventilating and heating system maintains a slight positivepressure in the switchgear room and control rooms to minimizethe entry of coal dust.

Startup panels for the main turbines are located at operatinglevel and adjacent to the turbines.

4 C b IMECHANICAL EQuiPMENT

The boiler is continuously rated at 250 000 pounds perhour of 610-psi 7800 F steam. It has a 72-inch-diameter

_ iN | :.drum and was designed to handle periodic steam flows upto 480 000 pounds per hour for short intervals of less than1 minute. The boiler is arranged for combination firingof four fuels: blast furnace gas, coke oven gas, pulverizedcoal, and oil.Two steam reducing valve control stations and one manual

bypass valve interconnect the new 600-psi steam headerwith the existing 400-psi system.The following boiler auxiliaries are driven by 400-psi

steam turbines: one 795-hp induced draft fan, one 223-

Fig. 11. Total fuel flow and air flow to boiler during strip mill hp forced draft fan, and two 100 per cent rated 400-hp boiler

operation, March 4, 1964 feedpumps. Electrically driven boiler auxiliaries are: two75-hp primary air fans, two 60-hp pulverizers, two 1/0.5-hp 2-speed coal feeders, two chemical feed pumps, 14 sootblowers, and one 7.5-hp ash handling water booster pump.

Steam Power Plant Arrangement Each turbine has a shaft-driven main oil pump. Low oilpressure automatically starts a steam turbine-driven auxiliary

EXISTING FACILITIES oil pump.

The 25/41-:\MW plant was built as an extension to a build- All other auxiliaries are driven by 550-volt motors: twoing housing fotur 400-psi boilers. Two 625-kW 575-volt 250-hp 75-kW main exciters (one per main generator),back pressure steam turbine-generators existed to supply two 30-hp condensate pumps, two 10-hp generator air coolerthe electrical auxiliairies of these four boilers. No other water booster pumps, two 3-hp gland condenser vacuumelectric generation existed at this site. It was possible pumps, and two 1-hp explosion-proof oil reservoir vaporto utilize the following existing facilities for the 25/41- extractors. Each condensate pump and each generatorMIW plant: the deaerator for existing boiler 4 was also used air cooler water pump is rated to handle maximum loadfor new boilei 5; the water treating plant was used for requirements of both turbine-generators. The unit notfeedwater makeul), coal handling, and other fuel facilities; in use serves as standby.the existing boilers were used to supply the new 400-psi There are two priming vacuum ejectors and two mainsteam driven auxiliaries; and the 625-kW generators were vacuum ejectors. Each ejector is rated to handle the re-used for 575-volt startul) power to the new electrically driven quirements of both main turbine condensers. The secondauxiliaries. ejector of each type serves as standby.

Each of the main condensing turbines is continuouslyP)HYSICAL AREANGEMENT rated 12.5 MW with a 600-psi 7700 F steam inlet and a

The existing steam plant building was extended to in- 3-inch-Hg-abs exhaust. Each generator is air cooled andcorporate the new power plant and control rooms. The continuously rated 11 kV, 12.5 MWV, 15.625 MVA, 0.8 PF,basement floor is at grade, and the operating floor is 18 and 3600 r/min, with field conditions of 96 volts and 500feet above. The basic plant consists of one 610-psi boiler amperes.

APRIL 1965 Fawcett-25/41-MW Cyclic Steam Power Plant 331

The short-time periodic peaking capability of each tur-bine-generator for intervals of less than 1 minute is 20.5MW, 27.4 MVA, with field conditions of 163 volts and 773amperes.

BoILEt CONTROL RoomThe boiler control room permiits the supervision and

loading control of the new boiler and the existing four boilers.New control boards were purchased to replace the manualXcontrol boards mounted locally at the existing boilers.These old boards have now been removed.

Startup of the boiler steam turbine-driven auxiliaries,boiler lightoff, and startup of the main turbines is fromlocal controls in the power plant.

Motor-driven auxiliaries can be started and stoppedlocally or from the boiler CODtrol boards. The controlboard for the new boiler 5 and the main turbine auxiliariesis shown in the right-hand portion of Fig. 12; the left-hand portion shows the controls for boilers 1, 2, and 3. Fig. 12. Control boards for new boiler 5, nain turbine auxil-

P'ressure transducers are mounted at the boilers andin the main turbine startup panels. The pneumatic sig-nals are transmitted in steel-armored multiple copper tubecables to the boiler control boards.

Annunciators are used as operating status indicators,as well as for alarm conditions. All annunciation is bothvisual and audible. The annunciator windows light up)in different colors to provide a means of classification cod-ing. Classifications are: conditions requiring immediateoperator action, an "off" condition of normally runningauxiliary motor or turbine, and an "off" condition of an aux-iliary motor which does not run at all times.

POWER DISPATCH RooMThe generator meters, synchronizing, and loading con-

trols are located on the right-hand side of the board shownin Fig. 13. This board also containis control for the newpumphouise, the power plant, and the existing boilerhouse 575-volt auxiliary systems.The board on the left is for telemetering and supervisory

control of the steel mill 11-kV ac plant distribution sys-tem. Fig. 13. Control boards for generators, pumphouse, andThe control boards are of the "dark board" type, i.e., power plant auxiliary systems; steel mill 11-kV telemetering

no lights are lit during normal operating conditions. A and supervisory controlplushbutton permits lamp tests for each major group oflamps. Annunciators are used in the sarne manner as withthe boiler control for color-coded visual and audible annuncia-tion of abnormal conditions. The power plant 11-kV switchgear is rated 13.8 kV 500

MVA and is standard air break nietalelad construction.ELECTRICAL SYSTEM AND EQUIPMEN~T The 1-MVA self-ventilated dry-type auxiliary trans-The single line diagram of the power plant ac system former is rated 11 kV-575 volts; provision has been made

is shown in Fig. 1. Startup power is available from the for a future 1.33-MVA rating using fans.existing boiler plant 575-volt turbine-generators and also For 575-volt service, the switehgear is 600-volt standardfrom the main substation 11-kV bus. The main substa- nmetal enclosed having 25 000- and 50 000-ampere draw-tion is ap)proximately 4000 feet from the power plant. out air breakers. Protection is obtained using current

All boiler and switchgear controls operate at 125 volts transformers, induction disk overcurrent relays, and 125-de via a system consisting of two supply buses and two volt dc shunt trip coils. The 250-hp exciter motors arenickel-cadmium batteries, each with automatic charger. controlled from breakers in this switchgear.Either battery can be switched to supply either or both The motor control center has combination starters usingbuses. Batteries can be temporarily paralleled for trans- current limiting fuses with a high rupturing capacity.fer, but this condition is annunciated to the dispatch room A terminal cubicle under eaeh generator contains currentto avoid leaving the batteries paralleled. The various transformer sets for metering, differential, and groundplant de loads are fed radially from the two supply buses overcurrent protection. A stainless-steel grounding re-through breakers. The open position of a breaker is an- sistor rated 1114 amperes for 8.2 seconds is also housed in,nunciated to the dispatch room, as well as low battery this cubicle.voltage and dc grounds. Connections from the generator terminals to this cubicle

332 Fawcett-25/41-MW Cycdic Steam Power Plant APRIL 1965

are by suitably supported factory-insulated rigid copper the steel plant in the event of sustained underfrequencybus. conditions.The excitation regulators are the high-speed magnetic

amplifier type with motor-driven 420 c/s permanent magnet NOMENCLATURE AND DESIGNATIONSgenerator control supply. Particular effort was exerted to standardize descriptiveThermal demand ammeters are used on feeders and large namies of equipment on civil, mechanical, and electrical draw-

motors. For motors installed in pairs with only one running ings. Engraved nameplates with name and equipmentat a time, operation hour indicators are provided. number were mounted on pushbuttons, motors, valves, con-

Time-delay undervoltage is provided to prevent shut- trolboards, etc.down, from voltage dips, of auxiliaries controlled by volt- These equipment designations and numbers in abbreviatedage held contactors. This control feature utilizes an off- form were used in designations for starters, associateddelay timer in each starter. To effect immediate inten- control and power cables, and interconnecting wire num-tional shutdown, the stop pushbuttons are of the pneumatic bers. The standard, which was achieved almost 100 pertime-delay type. When pressed, their contact opens imme- cent, was that each wire and every component it connecteddiately and stays open for 2 seconds. The off-delay timers to in all equipments would have only one designation whichare set at 1.5 seconds. would be marked on all terminal blocks and also on wire

markers. This degree of standardization was possibleEQUIPMENT PROTECTION- since most of the equipment was specified and assembled inThe majority of the protection is conventional, and the factories of one manufacturer. The installation drawings

only protection of particular interest will be mentioned were prepared by the same personnel. All control andhere. power wire insulation colors were indicated for each wireGround differential protection is provided on the 11-kV on the interconnection installation drawings. This facili-

switchgear using zero-sequence window-type current trans- tated connecting the cables.formers around all outgoing cables. Isometric drawings of the piping systems were mounted

Generator protection mounted on the 11-kV switch- behind glass in the power plant. These indicated thegear consists of high-speed phase differential, negative- valve designation numbers and were color coded the samesequence overcurrent, voltage controlled overcurrent, two as the actual piping color code.independent sets of generator neutral ground overcurrentrelays, and reverse power. Field undercurrent and field COOLING WATER PUMPHOUSEground alarm relays are located on the excitation regula- A new pumphouse was built at the lakeside, about 600tors. feet from the power plant. Four horizontal electrically

Stator temperature indication, alarm, and trip protection driven cooling water pumps were installed: two 800-hpare provided by 120-ohm resistance temperature detectors and units for the strip finishing mill and two 300-hp units for theWheatstone bridge equipment located on the generator power plant.control board. Similar equipment on the boiler control The 300-hp pumps discharge into a 36-inch pipelineboard monitors generator cooling air temperature and which supplies the following auxiliaries: main turbine con-lubrication oil temperature. For rotor temperature, a densers, vacuum ejectors, gland steam condensers, oilgraphic Kelvin bridge recorder with alarm contact is mounted coolers, generator air coolers. Water is returned to theon the generator control board. Only one recorder is pro- lake through a 36-inch line. A bypass valve permits watervided which, after initial operating periods with both ma- from the power plant to return to the pumphouse suctionchines, was permanently connected to one generator. Gener- during winter operation. Each 300-hp pump is 100 perator water detector alarms are provided. cent rated. Only one operates at a time, and the unit notThe turbines have the following standard protection in- in use serves as standby.

corporated in their oil control system: low lubrication and All pump motors are controlled at the power plant boilercontrol oil pressures, high and low oil level in the reservoirs, control room. The pumphouse is unattended and visitedlow vacuum, overspeed, and solenoid trip. To minimize once per shift by a power plant operator.overspeed when peak load has been rejected, an overspeed The pump motors are controlled from outdoor metalcladanticipation feature is provided to close the governor valves air break switchgear. This switchgear has two 2.4-kVwhen low generator current exists simultaneously with buses, each serving one 300-hp motor and one 800-hp motor.significant first stage steam pressure. Each bus is supplied from its own 1.5/2-MVA transformer.For protection of each 250-hp exciter motor, a special One of these transformers is fed from the power plant 11-

drawout-type relay was developed containing AIEE de- kV bus and the other from another part of the steel millvice 49 50 50G elements. Each motor at the pumphouse 11-kV system.is protected by a drawout-type relay containing AIEE The 2.4-kV bus tie breaker is normally open. Loss ofdevice 46 49 50 5OG and 51 elements. A drawout induction power at the secondary of either supply transformer is de-disk time-delay undervoltage relay is used with each fore- tected by a time delay undervoltage relay which trips thegoing motor for tripping. associated transformer secondary breaker. The tie breakerA slow speed underfrequency relay set at 54 c/s acts as then closes to re-energize the motors about 2 seconds after

backup to isolate the power plant and its auxiliaries from the loss ofpower.

APRIL 1965 Fawcett-2d5/41-MW Cyclic Steam Power PlanLt 333