ML20053A600

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Preliminary Study of Station Power Auxiliary Voltages
ML20053A600
Person / Time
Site: Big Rock Point File:Consumers Energy icon.png
Issue date: 05/18/1982
From:
CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:
Shared Package
ML20053A596 List:
References
NUDOCS 8205260291
Download: ML20053A600 (42)
v • d • e


Text

i 1

CONSUMERS POWER COMPANY ATTACHMENT 1 BIG ROCK POINT PLANT - PRELIMINARY STUDY OF STATION POWER AUXILIARY VOLTAGES l

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.s TABLE OF CONTENTS Page EXECUTIVE

SUMMARY

1

SUMMARY

OF RECOMMENDATIONS......................

3 4

INTRODUCTION.

PART I - VOLTAGE ASSUMPTIONS ANL EQUIPMENT RATINGS IA.

TURBINE GENERATOR VOLTAGE LIMITS 5

IB.

DIESEL GENERATOR VOLTAGE LIMITS.

5 IC.

SYSTEM VOLTAGE LIMITS - GENERAL.

5 ID.

SYSTEM VOLTAGE LIMITS - REGULATOR IN SERVICE 6

IE.

SYSTEM VOLTAGE LIMITS - REGULATOR OUT OF SERVICE.......

7 IF.

STATION POWER EQUIPMENT - ASSUMED VOLTAGE RATINGS AND LIMITATIONS.

8 PART II - REPORT OF MAXIMUM AND MINIMUM STEADY-STATE STATION POWER VOLTAGES DURING VARIOUS OPERATIONAL CONDITIONS IIA. BASE LOAD CONDITIONS - GENERATOR FEED.

9 IIB. LOCA CONDITIONS - 138 kV FEED.

13 14 IIC. LOCA CONDITIONS - 46 kV FEED IID. COLD SHUTDOWN CONDITIONS - 138 kV FEED 14 IIE. COLD SHUTDOWN CONDITIONS - 46 kV FEED.

15 IIF. UNIT START-UP CONDITIONS - 138 kV FEED 15 PART III - PROPOSED TAP CHANGES AND OPERATING RESTRICTIONS TO ALLEVIATE UNDERVOLTAGES PRESENTED IN PART IIA-F.

16 IIIA. TRANSFORMER TAP CHANGES.

IIIB. TURBINE GENERATOR OPERATION FOLLOWING THE MAIN TRANSFORMER 18 TAP CHANGE IIIC. STATION POWER VOLTAGES FOLLOWING THE MAIN TRANSFORMER 22 AND NO 11 AND NO 22 TRANSFORMER TAP CHANGES.

IIID.

SUMMARY

OF FINAL RECOMMENDATIONS (PARTS IIA-F) 22 PART IV - DIESEL GENERATOR OPERATION - MAXIMUM AND MINIMUM STEADY-STATE VOLTAGES 24 IVA.

LOSS OF 0FFSITE POWER - EMERGENCY LOADS............

28 IVB. EMERGENCY DIESEL GENERATOR - LOSS OF 0FFSITE POWER IVC. STANDBY DIESEL GENERATOR - LOSS OF OFFSITE POWER 29 IVD.

SUMMARY

OF RECOMMENDED DIESEL GENERATOR OPERATING VOLTAGES 31 i

e rp0182-0126a121-35 i

i Page PART V - STARTING THE LARGEST SAFETY-RELATED MOTOR - MINIMUM VOLTAGE CONDITIONS VA.

DESCRIPTION OF MOTOR - STARTING ASSUMPTIONS.

31 VB.

STARTING THE 100 hp FIRE PUMP - 138 kV FEED.

33 VC.

STARTING THE 100 hp FIRE PUMP - 46 kV FEED 33 VD.

STARTING THE 100 hp FIRE PUMP - DIESEL GENERATOR FEED (ANALYTICAL TECHNIQUE TO CALCULATE STARTING VOLTAGES).

33 VE.

STARTING THE 100 hp FIRE PUMP - EMERGENCY DIESEL GENERATOR 35 VF.

STARTING THE 100 hp FIRE PUMP - STANDBY DIESEL GENERATOR 36 REFERENCES.

37 l

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EXECUTIVE

SUMMARY

In response to NRC inquiries, the adequacy of the station power voltages on all safety-related equipment has been appraised for the Big Rock Plant.

Steady-state overvoltage and undervoltage conditions and motor starting transients under normal, LOCA (Loss of Coolant Accident), cold shutdown and diesel generator operation, coincident with a single failure, were examined.

The automatic voltage regulator (2400 V, t 5%, 250 kVA) is in series with both j

offsite power supplies. During minimum system voltage conditions and the-2400 V regulator in service, voltages at selected auxiliary equipment may fall below minimum requirements. Under normal, LOCf. and cold shutdown conditions, these deficiencies are corrected by adjusting the taps of the Station Power Transformers 11 and 22, and the main transformer.6 At rated output and system voltages above 140 kV, the modified main transformer tap may curtail over-excited generation capability to 40 Mvar (80% of rated). According to Plant records, a 20-30 Mvar output is typical during peak system conditions.

The automatic voltage regulator can be bypassed for maintenance or repair.

During minimum system voltage conditions and the 2400 V regulator out of se rvice, voltages at selected auxiliary equipment may fall below minimum i

requirements. These deficiencies can be corrected for normal and cold shut-down conditions by adjusting the taps of the Station Power Transformers 11 and 22 and the main transformer.6 Transformer tap changes will not correct undervoltage problems during LOCA and minimum system voltage conditions with the automatic voltage regulator out of service. Therefore, the unit must be r

taken off line and the station power loads reduced to cold shutdown levels when the automatic voltage regulator is nat available.

It should be noted, rp0182-0126a121-35 1

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i 1

4 however, that the voltage regulator requires only 2-3 days of preventive j

- maintenance per year and has not incurred a failure since the Plant began com-mercial operation in 1962.

l Onsite steady-state voltages will be adequate when using the emergency or standby diesel generator. The emergency' diesel generator may not have suffi-cient capacity to start the largest safety-related motor (100 hp fire pump) i" when preloaded to 160 kVA. Additional mocor and pump data are required to j

verify the capability of the emergency diesel generator to start and acceler-ate the 100 hp fire pump motor to full load speed.

If the data are not avail-3 1

able, a field test must be performed to verify cue capability of the emergency diesel to start and accelerate the motor to full load speed when preloaded to' j

160 kVA. No problems could be found using the standby diesel generator to

,i start and accelerate the 100 hp fire pump.

l The P-1161 computer model of the Plant was used in all voltage calculations.

i This simulation was verified by field tests in 1980 and has been used in f

l previous responses to the NRC.

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SUMMARY

OF RECOMMENDATIONS 1.

Change the main transformer tap from the 145/13.5 kV tap to the 140/13.5 kV tap.

2.

Change the No 11 station power transformer tap from the 2400/480 V tap to the 2340/480 V tap.

3.

Change the No 22 station power transformer tap-from the 2400/489 V tap to the 2340/480 V tap.

4.

Maintain the unit in a cold shutdown condition when the 2400 V, 250 kVA voltage regulator is out of service.

5.

Operate the emergency 480 V, 250 kVA diesel generator at a terminal volt-age of 480 volts during maximum and minimum loading conditions.

6.

Operate the standby 460 V, 312 kVA diesel generator at a terminal voltage of 483 volts during maximum and minimum loading conditions.

7.

Obtain additional data on the 100 hp fire pump to verify that the emer-gency diesel, when preloaded to 160 kVA, is capable of starting and accel-erating the 100 hp fire pump motor.

8.

If the data for the 100 hp fire pump are not available, perform a field test starting the 100 hp fire pump with the emergency diesel preloaded to 160 kVA and operating at a terminal voltage of 480 volts.

rp0182-0126a121-35

i 4

INTRODUCTION J

The following report is in response to NRC inquiries as to the adequacy of the station power voltages for all poasible operating conditions at the Big Rock Point Plant. Possible steady-state overvoltages and undervoltages have been 4

examined for the following Plant operating scenarios:

(a) base load condi-tions generator feed, (b) LOCA conditions - 138 kV feed, (c) LOCA condi-tions - 46 kV feed, (d) cold shutdown conditions - 138 kV feed, (e) cold I

shutdown conditicas - 46 kV feed, (f) unit. start-up conditions - 138 kV feed, (g) loss of offsite power - emergency diesel generator feed and (h) loss of offsite power - standby diesel generator feed. Each operating condition, if applicable, has been examined for maximum and minimum steady-state bus volt-ages with and without the 2400 V, 250 kVA voltage regulator in service.

Part I of the report summarizes the various voltage assumptions and station power equipment voltage ratings and limitations.

Part II is a summary and discussion of the maximum and minimum steady-state station power voltages for Plant Operating Conditions a.

through f.

Part III is a summary and discussion of possible transformer tap changes and operating restrictions to alleviate undervoltages presented in Part II.

Part IV summarizes the maximum and mini-mum expected steady-state voltages when using the emergency or standby diesel generator (Operating Conditions g. and h.).

Finally, Part V summarizes the maximum expected initial voltage transients when starting the largest safety-related motor during minimum voltage conditions while fed from the 138 kV, 46 kV or diesel generator (emergency or standby). All voltages have been calculated using the P-1161 computer model of the Plant which was verified by actual field testing in 1980 and has been used in previous responses to the NRC.

j rp0182-0126a121-35

5 PART I - VOLTAGE ASSU'iPTIONS AND EQUIPMENT RATINGS IA.

TURBINE GENERATOR VOLTAGE LIMITS The mr ximum turbine generator terminal voltage assumed for this study was analytically calculated to be 14.19 kV and is based on the present maximum voltage schedule of 143 kV and a maximum unit dispatch of 63 MW and 53 Mvar (overexcited). The minimum turbine generator terminal voltage assumed for this study was analytically calculated to be 12.59 kV.*

It is based on the present minimum voltage schedule of 140 kV and a maximum unit dispatch of 63 MW and 21 Mvar (underexcited).

IB.

DIESEL GENERATOR VOLTAGE LIMITS The maximum and minimum voltage ratings of the emergency and standby emergency diesel generators were assumed for this study to be t 5% of each diesel generator nominal voltage rating. Therefore, the 480 V emergency diesel generator has a maxioum voltage rating of 504 volts and a minimum voltage rating of 456 volts. The 460 V standby emergency

]

diesel generator has a maximum voltage rating of 483 volts and a mini-mum voltage rating of 437 volts.

IC.

SYSTEM VOLTAGE LIMITS - GENERAL Critical to the maximum and minimum station power voltages at the Big g

Rock Plant during LOCA, start-up or cold shutdown conditions are the

  • Typical manufacturer voltage ratings of generators are 5% of their nominal voltage rating. Therefore, the minimum voltage rating of the 13.8 kV turbine generator at Big Rock is 13.11 kV.

Operation at 12.59 kV is below the -5%

voltage rating but can be sustained without incurring overdutied conditions on the stator or exciter or falling belcw the steady-state stability limit.

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assumed 138 kV and 46 kV network voltages. These voltages were estab-lished by (1) reviewing nine months of hourly system operating voltages beginning in January-1981 and (2) analytically considering transmission network conditions over the next two years (1982 and 1983). The maxi-mum and minimum 138 kV and 46 kV transmission network' voltages were an-alytically determined using a single-failure criterion (Refer-ence GDC 17 and NUREG 75/087 II-1.b).

ID.

SYSTEM VOLTAGE LIMITS - REGULATOR IN SERVICE The maximum 138 kV voltage at the Big Rock Point Plant with the unit off line was determined to be 142 kV (1.029 pu).

This was established by reviewing Plant logbooks and correcting the readings based on meter calibration checks

  • performed in November 1981. Analytical studies in-dicate a maximum 138 kV voltage during light load conditions of 138 kV (1.00 pu) with the unit off line. However, analytical simulations of system light load conditions have proven to be difficult since capaci-tor on/off conditions and detailed area loadings during light load conditions are not readily known. Therefore, the higher historical voltage of 142 kV was used for maximum voltage calculations for-LOCA and cold shutdown conditions.

4 The minimum 138 kV voltage with the unit off line was analytically determiaed to be 131 kV (.95 pu) and assumes the Livingston 345/138 kV I

l transformer is out of service and that three peaker units are placed on line at Gaylord or the Straits peaker and one or more Gaylord peakers

  • Meter calibration checks indicate the 138 kV meter in the control room is reading 1 kV higher and the 2400 V No 7 Station Power Meter is reading l

'O volts higher than expected.

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IIistorical data indicate a minimum voltage of 134 kVL ~

(.971 pu). However, these' records do not necessarily refl~ect a single e

failure in the.transmissio'n system and system conditions projected s

Chrough. 1983. Therefore, the analy.tically calculated minimum voltage

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of 131 kV was'used for the minimum voltage calculations.

m The maximum 46 LV voltage pitli the unit of f Eline was determined to be 46 kV (1.'O pu). T'his'was'establishedbyrevi[ewingPlant.logbooksand

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s bysanalytically. calculating the' maximum 46]kV voltage through 1983.

Both -snalytical ands historical methods established 46 kV "~(1.00 pu) to be the maximum bus valtage.

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The minimum 46 kV vol"tage with the unit off line was analytically,

determitied to be 42 kV. (.91 pu).

This assumes the Big Rock to Emmet

.s 138 kV line is 'out of service since automatic transfer to the 46 kV -

hffsite supply occurs only whpn the 2400'V bus voltage drops below 50%.

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s IIistorical data indicate a minimum voltage of 44 kV (.96 pu) but does notgeflectsystemconditione,projectedthrough1983.

IE.

SYSTEM VOLTAGE LIMITS - REGULATOR OUT OF SERVICE In order to establish the maximum and7ninimum 138 k$ voltages, a single failure' criterion was used. Thus any single complinent feeding the s'tation power supply must be considered when evaiusting the maximum and minimum voltages throughout'the Plant. The 2400 V voltage regulatori can be bypassed and taken out of service by pening and closing avail-able 2000 A Delta-Star disconnect switches (Reference WD 740 Sheet 1).

-s Once the regIriator is taken out of service, it is considered a aingle

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failure. T$us,maximumandminimum138kVsystemvoltageswiththe regulator out.of service are establishe.d assuming normal system oper-ating conditLons. The maximum 133 kV voltage with the regulator out of service-is the sa.me as with it in service and was established as out-linedinha'rt(ICrtobe142kV(1.02[9pu). The minimum voltage, how-ever, was established to be 134 kV (.971 pu) and is based on historical operating data with th unit off line and analytical calculations

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througk 1983. Maxim 6m. tid m'inimum. voltages for the'46 kV system were not established with the 2400 V regulator out of service _since transfer to the 46'k'/" system would represent a double contingency (2400 V regu-lator out. of 's'_er!Vice and loss of the-138 kV Emmet-Big Rock feed).

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IF.

STATION POWER EQyIPMENT ASSUMED VOLTAGE RATINGS AND LIMITATIONS -

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The foliawing voltage limits' were assumed for the station power equip '

q ment at the Big Rock Potat! Planti 440 V motors i 10%,of nominal (1.008 pu max and.825 pu min), 460 V motors t 10% of nominal (1.056 pu max arid.863 pu min), 2300 V motors 10% of nominal.(1.054 pu max and 5

,.863;pu min), 48C V battpry chargers 10% of nominal (1.10 pu max'and 190 pu min, fed from MCC'2A), 480 V AC Contactors.85.ps pi,ckup and

.65 pu dropout.* Ttfe most limii.ing minimum egnipment voltages occur on

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the 120 V instrumentation and co'ntrol (I&C) p9wer supp les which have the following maximum and mintmum voltage 'atings as ::een at 480 V,

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  • Based on_ananufacturer's reco'mmendations. Actual tests may provide different

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9 Bus IA Voltage Limit 1

(480 V Base)

Power Supply Max Min ES8512A 1.068

.901 ES8512B 1.068

.901 ES2108 1.078

.910 ES3171 1.066

.874 ES2165 1.093

.897 ES2160 1.069

.878 ES2162 1.069

.878 ES2161 1.063

.871 ES2163 1.063

.871 In addition to these equipment voltage limits, the 2400 V undervoltage relays drop out at 89% of nominal.and trip the 2400 V bus after a ten-i second time delay trar.sferring station power loads to the emergency diesel generator. This places an additional limitation on the accept-able station power voltage as seen at the 2400 V bus.

P/.RT iI - REPORT OF MAXIMUM AND MINIMUM STEADY-STATE STATION POWER VOLTAGES DURING VARIOUS OPERATIONAL CONDITIONS IIA.. BASE LOAD CONDITIONS - GENERATOR FEED

_. ' Maximum and minimum station power voltages have been calculated for the l

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. base load generator feed conditions and are summarized in Table 1 (2400 V Regulator in Service) and Table 2 (2400 V Regulator Out of Se rvice).

A transcription of the assumed base case conditions is i

. '. presented in Figure 1.

No overvoltages occur with or without the 2400 V regulator in service for present maximum generator voltage con-j 1

ditions of 14.19 kV.

No undervoltages on station power equipment occur i

during present minimum generator voltage conditions of 12.59 kV with

,w' the 2400 V regulator in service. However, with the 2400 V regulator i,

out of service and the minimum generator voltage of 12.59 kV, the rp0182-0126a 121-35 e

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ES TABI.E 1 E

Summary of Station Power Voltages - Regulator in Service (Paesent Taps)

S 138 kV 46 kV 2400 V 480 V 480 V 480 V 440 V

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Plant Operating Condition Bus Bus Gen Term

_Swgr_ MCC 2A HCC IA HCC 2B Fire P (13.5 kV Base)

(480 V Base) eed, Max V 1.036 1.05 1.003

.950

.950

.950 0FF Base I.oad - Cencrator r Base f.oad - Generator Feed, !!in V 1.014

.932

.971*

.915

.916

.916 0FF I.0CA - 138 kV Feed, Hax V 1.029

.971

.998

.940

.92f

.925

.913 f.0CA - 138 }V Feed, Hin V

.95

.895

.926*

.861

.846

.845

.831 IDCA - 46 kV Feed, Max V 1.00 1.003

.951

.935

.934

.921

.975*

.920

.904

.903

.890 f.0CA - 46 kV Feed, Hin V

.91 Cold Shutdown - 138 kV Feed, Hax V 1.029

.977

.997

.949

.959

.959 0FF

.902

.962*

.917

.922

.922 OFF Cold Shutdown - 138 kV Feed, Hin V

.95

.99/

.949

.959

.959 0FF Cold Shutdown - 46 kV Feed, Hax V 1.00 Cold Shutdown - 46 kV Feed, Hic l'

.91

.985*

.941

.946

.946 0FF

  • 2400 V regulator on last available tap KEY 1/4/82

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Sinmnary of Station Power Voltages - Regulator Out of Service (Present Taps)

S ta 1

480 V 480 V 480 V 440 V t

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Plant operating Condition 138 kV llus Gen Term 2400 V Swgr HCC 2A HCC IA tlCC 28 Fire P (13.5 kV ilase)

(480 V Base) j i

liase 1.oad - Generator Feed, Hax V 1.036 1.05 1.045

.994

.994

.994 0FF Base laad - Generator Feed, Hin V 1.014

.932

.920

.361

.861

.861 0FF IDCA - 138 kV Fecil, Hax V 1.029

.971

.958

.897

.883

.882

.869 1.0CA - 138 kV Feed, Hin Vk

.971

.915

.898

.331

.815

.814

.799 Cold Slintdown - 138 kV Feed, Max V 1.029

.977

.991

.949

.953

.953 0FF Cold Shutdown - 138 kV Feed, Hin V*

.971

.922

.934

.887

.893

.893 0FF i

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  • Assumes the regulator out of service as the single failure for establishing the minimum system voltage l

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DIG ROCK PL Ah1T 2.9 I. 0 % 't 12 MAIN TRF.

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voltage on MCC 1A drops to.861 pu which is below the minimum voltage ratings of the I&C power supplies summarized in Part IF of this report.

In addition to these I&C power supplies, the battery chargers fed from MCC 2A will be subjected to a.861 pu voltage which is 4.3% below their

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minimum 90% rating. Motors rated 460 V will also be subjected to

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slight undervoltages throughout the Plant (Class IE motors, however, j

are rated 440 V and will not be subjected to undervoltaged conditions),

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IIB.

LOCA CONDITIONS - 138 kV FEED

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l Maximum and minimum station power voltages have been calculated for f

LOCA - 138 kV feed conditions and are summarized in Table 1 (2400 V Regulator in Service) and Table 2 (2400 V Regulator Out of Service).

No overvoltages occur with or without the 2400 V regulator in service during LOCA conditions for maximum system voltage conditions of 142 kV (1.029 pu). Undervoltages will occur with the 2400 V regulator in f

service and a minimum 138 kV voltage of 131 kV (.95 pu) on all 460 V rated

  • motors, all I&C power supplies fed from MCC 1A and the battery chargers fed from MCC 2A (see Table 1).

In addition to these under-l voltages, the minimum required pickup voltages on 480 V AC Contactors 4

(assuming manufacturer recommended ratings) fed f rom MCCs IA, IF,1C, i

ID, IE, IP and 2B are below 85% and are considered marginal. Under-voltages will also occur with the 2400 V regulator out of service and a minimum 138 kV voltage of 134 kV (.971 pu) on all 460 V and 4 '3 V l

motors ' including Class IE motors), all I&C power supplies fed from MCC 1A and the battery chargers fed from MCC 2A (see Table 2).

In

  • Class IE motors at Big Rock are rated 440 V and will nc be subjected to undervoltage conditions with the regulator in service.

rp0182-0126a121-35 I

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14 addition, 480 V AC Contactor voltages on all MCCs are below 85% and may not pick up.

IIC. LOCA CONDITIONS - 46 kV FEED Maximum and minimum station power voltages have been calculated for LOCA - 46 kV feed conditions and are summarized in Table 1 (2400 V Regulator in Service). Maximum and m!k mum station power voltages were not calculated for LOCA conditions - 46 kV feed conditions with the 2400 V regulator out of service since transfer to the 46 kV supply occurs only if the 2400 V bus voltage drops below 50%. This would represent a double contingency (2400 V regulator out of service and the loss of the Emmet-Big Rock 138 kV feed). No overvoltages occur with the 2400 V regulator in service during a LOCA for the maximum 46 kV voltage of 46 kV (1.0 pu).

A slight undervoltage (see Table 1) occurs on I&C Power Supply ES2108 with the regulator in service and a minimum 46 kV voltage of 42 kV (.91 pu).

o IID. COLD SHUTDOWN CONDITIONS - 138 kV FEED Maximum and minimum station power voltages have been calculated for cold shutdown - 138 kV feed conditions and are summarized in Table 1 (2400 V Regulator in Service) and Table 2 (2400 V Regulator Out of Service). No overvoltages occur with or without the 2400 V regulator in service during cold shutdown conditions for maximum cystem voltage conditions of 142 kV (1.029 pu). No undervoltages on station power equipment occur during cold shutdown with the 2400 V regulator in service and a minimum system voltage of 131 kV (.95 pu).

However, with i

i rp0182-0126a l21-35 i

J 15 i

the 2400 V regulator out of service and a minimum system voltage of 134 kV (.971 pu), undervoltages will occur on I&C Power Supplies ES8512A, ES8512B, ES2165 and ES2108. The battery chargers fed from Bus 2A will also be undervoltaged 1.4% below their micimum 90% rating (see Table 2).

i IIE. COLD SHUTDOWN CONDITIONS - 46 kV FEED Transfer to the 46 kV supply during cold shutdown conditions will occur only if the 138 kV normal offsite feed is unavailable. Therefore, cold-shutdown conditions were examined only with the 2400 V regulator in service since conditions with it out of service represent a double contingency (2400 V regulator out of service and the 138 kV Emmet to I

i Big Rock feed out of service). No overvoltages occur with the 2400 V regulator in service during cold shutdowt conditions for a maximum i

46 kV bus voltage of 46 kV (1.00 pu). No undervoltages occur with the I

2400 V regulator in service and a minimum 46 kV voltage of 42 kV i

(.91 pu). The voltages during cold shutdown - 46 kV feed conditions are summarized in Table 1.

IIF.

UNIT START-UP CONDITIONS - 138 kV FEED Steady-state maximum and minimum station power voltages were not exam-ined during unit start-up condition since maximum steady-state voltages

)

occur during cold shutdown conditions (minimum Plant load) and minimum i

steady-state voltages occur during LOCA conditions (maximum Plant load).

rp0182-0126a 121-35

16 PART III - PROPOSED TAP CHANGES AND OPERATING RESTRICTIONS TO ALLEVIATE UNDERVOLTAGES PRESENTED IN PART IIA-F 3

IIIA. TRANSFORMER TAP CHANGES The 138 kV system is used for the primary offsite station power feed for LOCA, cold shutdown and start-up conditions and is made possible by the use of the generator breaker (Reference WD 740, Sh 1, Brkr 116).

Figure 2 is a simplified one-line diagram illustrating the major compo-S nents feeding the 2400 V and 480 V station power systems. Tap changes were studied on the main transformer, 13.8/2.4 kV station power trans-former and 2400/480 V Transformers No 11 and No 22 (see Figure 2) to alleviate the undervoltages outlined in Part II of this report. The main transformer is set on its highest tap position of 145/13.5 kV which results in maximum voltage " boost" when the unit is on line but also results in maximum voltage reduction when feeding the station power supply via the 138 kV system during unit shutdown or start-up conditions. The transformer has two alternate tap positions of 135/13.5 kV and 140/13.5 kV.

The 13.8/2.4 kV station power transformer is currently set on its lowest tap position of 13.2/2.4 kV.

The 2400/480 V transformers are' set on their nominal tap position but have four 2.5% taps available ( 5%). The 2400 V, 250 kVA voltage regulator provides 1 5% regulation.

Setting the 2400/480 V station power banks on the 2280 V (-5%) tap re-sults in excessively high voltages on 440 V motors during base load conditions and cold shutdown conditions (light station power loads) with or without the regulator in service. Setting the main transformer rp0182-0126a 121-35 1

. - - _ ~ __

~

FibURE

'Z PRi m A RN C Q'S ITE SUPPLY - B l(a Rn 17 1

I?S KY T

14 5 MAN TRF 41 (TVn m

f 13.6 tv l'5.1 6P TW *i crm l

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on the 135/13.5 kV tap position results in severe generator Hvar re-strictions while operating in the overexcited mode.

It was found, however, that the combination of changing the main transformer to the 140/13.5 kV tap and the 2400/480 V transformers to the 2340/480 V tap would alleviate undervoltaged conditions for all Plant operatirg condi-tions with the regulator in service and a degraded 138 kV system volt-age of 131 kV (.95 pu). Table 3 summarizes the undervoltage problems outlined in Part IIA-F of this report and the resulting problems after the proposed tap changes to the No 11 and No 22 station power trans-formers and main transformer are implemented.6 As can be seen in Table 3, tap changes will not alleviate undervoltaged conditions during a LOCA with the 2400 V regulator out of service and a 138 kV system voltage of 134 kV (.971 pu).

Therefore, operation without the 2400 V voltage regulator in service must-be restricted.

IIIB. TURBINE GENERATOR OPERATION FOLLOWING THE MAIN TRANSFORMER TAP CHANGE Changing the main transformer tap from the 145/13.5 kV tap setting to the 140/13.5 kV setting is illustrated in Figures 3 and 4.

Each plot shows the generator terminal voltage (13.8 kV base) and net unit Mvar capability in the underexcited and overexcited mode. As can be seen in Figure 3, the 140/13.5 kV tap will limit the generator to a 40 Mvar net output (overexcited) due to generator vcitage restrictions of 14.5 kV (1.05 pu).

The 40 Mvar net capability, however, should be sufficient during peak system conditions and the present maximum voltage schedule of 143 kV (Plant log readings indicate a 20 to 30 maximum Mvar net output is typical during peak system conditions). Generator terminal rp0182-0126a121-35 ee----

t 1

TABLE ?

Sununary of Undervoltages and Effect of Proposed Tap Change 1

i i

a l

Description of Undervoltaged Equipment Plant Operating Condition Present Tap Settings Proposed Tap Settings Base Load - Generator Feed, flin V, I&C Supplies, Battery Chargers, None Regulator Out of Service 460 V Hotors LOCA - 138 kV Feed, Hin V, Regulator in I&C Supplies, Battery Chargers, None Service 460 V Hotors, AC Contactors LOCA - 138 kV Feed, Hin V, Regulator I&C Supplies,. Battery Chargers, I&C Supplies ES8512A, ES8512B, Out of Service 460 V and 440 V Hotors, AC ES2108 and ES2165, Battery Chargers

  • Contactors 1,0CA - 46 kV Feed, Hin V, Regulator in I&C Supply ES2108 None Service Cold Shutdown - 138 kV Feed, Hin V, I&C Supplies ES8512A, ES8512B, None Regulator Out of Service ES2108 and ES2165, Battery 1

I Chargers s

I h

  • Restrict unit operation without voltage regulator l

KEY 1/4/82 ge rp0182-0126e121 i

Figure 3 BIG ROCK GSU XFliR-143KV SYSTEli VOLTAGE (63l1H DISPATCH) 1.100-j

~

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-25

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5 10 15 20 25 30 35 40 45 50 55 60 65 mvars-net O

rey W/n 8

Figure 4 BIG ROCK GSU XFMR-140KV SYSTEH VOLTAGE (63(1H DISPATCli) i.100.

a

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voltages will be improved (see Figure 4) in the underexcited mode for the minimum voltage schedule of 140 kV.

Final maximum and minimum generator terminal voltages are expected to be 14.5 and 13.1 kV with the lower main transformer tap setting (see Figures 3 and 4).

4 IIIC. STATION POWER VOLTAGES FOLLOWING THE MAIN TRANSFORMER AND NO 11 AND

}

NO 22 TRANSFORMER TAP CHANGES Table 4 summarizes the expected steady-state station power voltages af ter the transformer tap changes are implemented. Unit operation without the 2400 V voltage regulator is assumed to be restricted. Bus voltages are expected to approach 439 volts during cold sh'atdown condi-j tions without the 2400 V voltage regulator in service and a maximum 138 kV voltage of 142 kV (1.029 pu). Actual 440 V motor terminal volt-ages, however, will be below their maximum 110% voltage ratings due to 1

mocor feeder cable voltage drops not indicated in Teble 4.

IIID.

SUMMARY

OF FINAL RECOMMENDATIONS (PARTS IIA-F)

In order to alleviate the undervoltages as outlined in Parts IIA-F of this report, the following tap changes and operating restrictions are recommended:

1.

Change the main transformer tap from the 145/13.5 kV tap to the i

140/13.5 kV tap.

l i

2.

Change the No 11 transformer tap from the 2400/480 V tap to the 2340/480 V tap.

t i

rp0182-0126a121-35 f

TABLE 4 Summary of Station Power Voltages - Proposed Transformer Taps 138 kV 46 kV 2400 V 480 V 480 V 480 V 440 V Plant Operating Condition Bus Bus Gen Term Swgr MCC 2A MCC 1A MCC 2B Fire P (13.5 kV Base)

(480 V Base) l Base Load - Generator Feed, Max V 1.0f6 1.073 1.01

.984

.985

.985 0FF J

Base Load - Generator Feed, Min V 1.014

.971 1.01

.984

.985

.985 0FF t

LOCA - 138 kV Feed, Max V 1.029 1.007 1.002

.972

.959

.957

.946 LOCA - 138 kV Feed, Min V

.95

.928

.963*

.928

.915

.914

.901 LOCA - 46 kV Feed, Max V 1.00 1.003

.978

.963

.962

.950 LOCA - 46 kV Feed, Min V

.91

.975*

.947

.931

.930

.917 Cold Shutdown - 138 kV Feed, Max V 1.029 1.012 1.003

.986

.991

.991 0FF Cold Shutdown - 138 kV Feed, Min V

.95

.934

.997

.981

.985

.985 0FF Cold Shutdown - 46 kV Feed, Max V 1.00 1.003

.986

.991

.991 0FF

{

Cold Shutdown - 46 kV Feed, Min V

.91

.985* -

.968

.972

.972 0FF Cold Shutdown - 138 kV Feed, Max V 1.029 1.012 1.028 1.014 1.018 1.018 0FF Reg 0/S**

1

  • Regular on last tap
    • 0nly case with regulator out of service 3

KEY 1/4/82 rp0182-0126fl21-142 l

1

24 3.

Change the No 22 transformer tap f-om the 2400/480 V tap to the i

2340/480 V tap.

4.

Maintain the unit in a cold shutdown condition when the 2400 V, 250 kVA voltage regulator is out of service.

PART IV - DIESEL GENERATOR OPERATION - MAXIMUM AND MINIMUM STEADY-STATE 1

VOLTAGES t

IVA.

LOSS OF OETSITE POWER - EMERGENCY LOADS I

Essential station power loads are maintained by either the 480 V, 250 kVA emergency diesel generator or the recently installed 460 V, 312 kVA standby emergency diesel generator upon loss of offsite power.

Assistance was provided by Plant personnel in determining the sequencing of essential station power loads onto the emergency diesel f

generator, following loss of offsite power, and are sunmarized in Table 5.

Maximum equipment voltages occur during the first 1/2 hour (minimum loading conditions). Minimum equipment voltages occur after-all loads are sequenced on line including the 100 hp fire pump (maximum loading conditions).

Figures 5 and 6 are one-line diagrams summarizing the locations of essential loads and the final electrical system fed by 1

i each diesel generator (emergency and standby) upon loss of offsite t

I' power.

I i

i l

l rp0182-0126a 121-35

. ~ _

25 TABLE 5 Summary of Station Power Loads - Loss of Offsite Power A.

Immediate Loads (breaker numbers in parentheses)

Load I&C Transformer 2B (2B )

11-15 amp Gland Seal Exhauster No 2 (2B21) 2 amp Substation Service (IA32) 6 amp RDS - UPS A (IA64) 2 amp RDS - UPS B (IA13) 2 amp Emergency Bearing Seal Oil Pump (2A22) 11 amp Panel 2P Supply (2A14)*

12 hp + 18 kW RDS - UPS C (2Ab5) 2.5 amp RDS - UPS D (2A16) 2.5 amp No 3 Air Compressor (2A35) 22 amp Canal Sample Pump (IC23) 1 amp Well House Supply (IC25) 18 amp B.

Additional Load Within 30 Minutes of Loss of Power Load Control Rod Drive Pump (1A57 or 2A58) 40 hp C.

Additional Loads 1 Hour After Loss of Power Load Station Battery Charger (2A32) 7 amp Demineralized Water Pump (IE22) 5 hp Heating Boiler Auxiliaries (IA33)**

5 hp Screenhouse Heater (IC13A)**

24 kW D.

Additional Load 8 Hours Atter Loss of Power Load Emergency Lighting (from station battery) 30 amp E.

Other Loads Load Personnel Air Lock (2B22) 5 amp Equipment Air Lock (2B25) 6 amp

  • Clean and dirty sumps, lighting Transformers 4 and 5, and poison tank heaters
    • Cold weather only KEY 1/4/82 rp0182-0126a 121-35

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a 28 IVB. EMERGENCY DIESEL GENERATOR - LOSS OF 0FFSITE POWER 1

The 480 V, 250 kVA emergency diesel generator is connected directly to 480 V Bus 2B via 300 feet of 350 kemil cable (see Figure 5).

Past L

emergency diesel generator auto test procedures were reviewed in order to establish the current acceptable operating generator terminal volt-ages of 490-480 volts. Load flow cases were run at 490 V (as indicated I

in Plant auto test start procedures) and minimum loading conditions.

Additional load flows were also run at a terminal voltage of 480 V with minimum loading conditions. Table 6 summarizes the maximum equipment voltages for 490 and 480 volt generator terminal voltages. As can be seen in Table 6, overvoltages occur on several 440 V motors with an operating voltage of 490 volts while no overvoltages occur with the 480 V operating voltage. Therefore, the recommended diesel generator voltage during loss of offsite power should be 480 V to avoid over-voltages on 440 V motors during minimum diesel generator loading conditions.

Load flow cases were run at the minimum acceptable 480 V operating voltage (as indicated in Plant and test start procedures) and maximum j

diesel generator loading conditions. Total connected station power l

loads will approach 314 kVA. Approximately 21.6 kVA, however, is i

3 considered intermittent load and is not included in the steady-state i

continuous loading. These loads include the RDS-UPS supplies, station battery chargers, personnel lock and equipment lock. Thus, the resul-i t

tant diesel generator load will be 292 kVA. An additional 38 kVA of 1

load can be shut down if the loading of the diesel, which is closely i

i rp0182-0126a121-35 i

29 monitored during Plant emergency conditions, approaches the maximum 275 kVA rating (as indicated by Michigan Tractor ).

Thus, the 250 kVA diesel generator has adequate kVA capacity to maintain the unit in a safe shutdown condition. Table 6 summarizes the minimum station power voltages with a maximum diesel generator loading of 260 kVA (assumes approximately 33 kVA of load has been shut down) and a minimum oper-ating voltage of 480 V.

As can be seen in Table 6, all operating volt-ages are adequate.

IVC.

STANDBY DIESEL GENERATOR - LOSS OF 0FFSITE POWER The 460 V, 312 kVA standby diesel generator is connected to 480 V Bus 2B as indicated in Figure 6.

Past standby diesel generator load test procedures were reviewed in order to establish the current acceptable operating generator terminal voltages of 456-504 volts.

Operating at a generator terminal voltage of 504 volts exceeds the generator voltage rating of 483 volts (see Part IB) and will result in overvoltages on 440 V induction motors during minimum loading condi-tions. Operating at a generator terminal voltage of 456 volts will result in undervoltages on I&C supplies fed from Bus IA and battery chargers fed from Bus 2B during maximum loading conditions.

Load flow cases were run at 460 volts (the nameplate rating of the diesel genera-tor) and 483 volts (the maximum rating of the diesel generator) during maximum loading conditions and are summarized in Table 6.

As can be seen in Table 6, even operating at 460 volts (the diesel nameplate rating) will result in undervoltages on Buses IA and 2B.

Operation at 483 volts, however, results in acceptable station power voltages during rp0182-0126al21-35

l TABLE 6 Diesel Generator - Summary Max and Min Voltages Emergency Diesel Generator Standby Emergency Diesel Generator 13us or Load Max V - 490 Max V - 480*

Hin V - 480*

Max V - 483*

Hin V - 483*

Min V - 460 MCC 1A 1.012

.992

.972

.990

.943

.894 Sub Service Control Rod No 1 HCC IC 1.011

.990

.967

.989

.939

.890 Canal Sample 1.010**

.990

.967

.988

.943

.889 MCC IF 1.012

.992

.971

.990

.943

.893 MCC IE 1.012

.992

.971

.990

.942

.892 HCC 2A 1.015

.994

.956

.993

.927

.877 Emer Bearing P 1.012**

.991

.952

.990

.924

.874 Air Comp No 3 1.012**

.992

.953

.990

.924

.874 Control Rod No 2

.948

.919

.869 MCC 2P MCC 2B 1.015

.995

.973

.993

.945

.895 Personnel Lock Fire PP

.962

.933

.882 I&C XFMR 2B 1.014

.994

.973

.992

.944

.894 Gland Seal Ex No 2 1.014**

.99.

.972

.992

.943

.894

]

Diesel Terminals 1.021 1.000 1.000 1.006 1.006

.958 i

o

-Off

  • Recommended max or min voltage for corresponding diesel
    • Above 110% rating of'440 V motor 8

KEY 1/4/82 rp0182-0126hl21-142

31 maximum and minimum loading conditions. Therefore, the standby diesel generator should be operated at a terminal voltage of 483 V during maximum and minimum loading conditions to provide adequate voltage profiles to essential station auxiliary equipment.

IVD. SLHMARY OF RECOMMENDED DIESEL GENERATOR OPERATING VOLTAGES 1.

Operate the emergency 480 V, 250 kVA diesel generator at a terminal voltage of 480 volts during maximum and minimum laading conditions.

(Operation at 490 V will result in overvoltages on 440 V motors during minimum loading conditions.)

i 2.

Operate the standby 460 V, 312 kVA diesel generator at a terminal j

voltage of 483 volts during maximum and minimum loading conditions.

(Operation at 504 volts exceeds the diesel generator voltage rating and will overvoltage 440 V motors during minimum loading condi-4 tions. Operation at 460 volts will result in undervoltages on i

station auxiliary equipment during maximum loading conditions.)

PART V - STARTING THE LARGEST SAFETY-RELATED MOTOR - MINIMUM VOLTAGE CONDITIONS Va. DESCRIPTION OF MOTOR - STARTING ASSUMPTIONS The largest safety-related motor which may be required to start during minimum voltage conditions is the 440 V, 100 hp fire pump which is fed from 480 V MCC 2B.

Motor starting cases were studied using the P-1161 model of the Plant during LOCA 138 kV and 46 kV feed conditions as well as loss of offsite power diesel generator feed conditions.

In all rp0182-0126a121-35 I

32 cases, the fire pump motor feeder cable was included in the voltage drop calculations.

In order to determine the ability of an induction motor to start and accelerate its load, the following minimum test data must be available:

1.

Motor and load WK 2.

Motor no-load test data 3.

Motor blocked rotor test data 4.

Load speed torque curve Items 2 and 3 are used to calculate equivalent circuit data. Motor speed torque and current vs speed curves can then be calculated from the equivalent circuit of the motor during start-up (if not provided by the manufacturer). None o' the data previously listed, however, is available for the 100 hp fire pump. Typical Class 1E motors are normally' capable of starting and accelerating their loads provided at least 70% of rated terminal voltage is available during start-up.

While voltage below 70% may not necessarily result in the motor being unable to start and accelerate its load, the 70% voltage requirement can be used to indicate potential design deficiencies in Plant Auxiliary Systems during motor start-ups. The voltages reported during the fire pump start-ups are the first initial motor terminal voltage transient when starting the motor. Throughout the remaining sections of this report, a motor starting voltage of less than 70% of the 440 V nameplate rating of the motor is considered a design deficiency rp0182-0126a 121-35 i

i

~~

4 33 i

requiring either (a) additional motor and load data to analytically determine if the motor can accelerate its load or (b) actual field testing of the motor starting under minimum voltage conditions.

VB.

STARTING THE 100 hp FIRE PUMP - 138 kV FEED Motor starting cases were run during LOCA minimum 138 kV voltage condi-i tions with the present and proposed transformer tap. settings and are summarized in Table 7.

As can be seen in Table 7, the motor terminal voltage is far above the minimum 70% voltage rating (as outlined in Part VA) of the motor during start-up.

VC.

STARTING THE 100 hp FIRE PUMP - 46 kV FEED Motor starting cases were run during LOCA minimum 46 kV voltage condi-l tions with the present and proposed transformer tap settings and are summarized in Table 7.

As can be seen in Table 7, the motor terminal voltage is far above the minimum 70% rating (as outlined in Part VA) of the motor during start-up.

VD.

STARTING THE 100 hp FIRE PUMP - DIESEL GENERATOR FEED (ANALYTICAL j

TECHNIQUE TO CALCULATE STARTING VOLTAGES) l f

Starting an induction motor using a diesel generator requires simula-i tion of the diesel generator excitet capability to provide adequate voltage throughout the motor acceleration period. As was pointed out i

i in Part VA of this report, data is not available to properly calculate the accelerating torque of the 100 hp fire pump during start-up.

A i

motor terminal voltage lower than 70% of the motor rating, however, may i

i rp0182-0126a121-35 t

r I

TAB 11 7 Sununary of Voltages - Fire Pump Start-Ups i

Fire Pump Terminals Plant Operating Condition 2400 V Bus MCC 2B (480 V Base)

(440 V Base) 1.0CA 138 kV Feed, Minimina V

.919

.785

.811 Present Taps 1.OCA 138 kV Feed, Minimum V

.955

.846

.874 New Taps j

l.0CA 46 kV Feed, Miniatun V

.963

.823

.843 Present Taps LOCA 46 kV Feed, Minimtun V

.963

.847

.868 New Taps i

Emergency Diesel Generator Feed

.648

.652

.658*

Generator at 480 V Emergency Diesel Generator Feed

.677

.681

.700 Generator at 483 V L

r 3

i.

  • Below the assumed 70% rat.ing of the motor KEY 1/4/82 io rp0182-0126il21-142

c;

, s r/

c.

+

~

q..

s m'

l-

'35 g.-

i l'adicate potential motor starting problems.

In order to simulate the first initial. voltage drop while starting the 100 hp fire pump, the tbllotJing aca~1ytical technique was used:

\\ -,

j

^

1.

Estabissh the preload kVA on the diesel generator and running' terminal voltage 2.

Establish the voltage behind subtcansient 'r'e'actance' a

y

_.s e

A 3.

Start tb4 100 hp fire pump using loc [ted rotor current and. st!' art.ing e

I power factor data t,. _

VE.

STARTING.THE 100fhp FIRE PUMP - EMERGENCY DIESEL GENERATOR Starting the 100 L, fire pump using the 480 V, 250 kVA emergency diesel

' generator was examined with a preload of 160 kVI ar$d the recommended

.s o[>cfatingterminalvoltageof480V(1.0pu)presenpedinPartIVBof-this report. As ran be seen in Table 7, the motor terminal voltage q

2 drops 3o 45,$% 'w,hich is below the assumed 16% minimum starting voltage 1,

s rati}nd of theictor. Critical = to det'ermining the initial voltage transient during the motor start-up is the diesel generator terminal d

voltage and resciting voltage behind subtransient rea.ctance.

It was c

' - found that operating the diesel generator at higher-voltages will a

overvoltage 440 V, motors (see'h rt IVB) and will not bring the initial 4

Ob voltage transient equal to' or above the assumed einimum? 70% rating of,

1 the motor. As was pointe.d o'dt in Part VA of'this report, an i.nitial, c--

l voltage transl,ent of 65.8% does not necessarily mean the, motor will be unable t'o star't' -and ~aecelerate to fuf1 load speed.

Ho'ever, the calcu-w latedvoltagesdoindicatethepossibilitythatitwd'lnotbecapable

,p i

.:) '

rp0182-0126a121-35 s

(

f.

x

h 1

36 m

s.

4

. s of; starting and act.el[ rating its lo'ad.to full load speed and that fur-ther studies must be made.

The re fcire, it-is recommended to (1) try to obtain from the motor and pump s.anulacturer the necessary data to ana-e v.

i lytically determine if the motoc will s, tart and accelerate.it.s load to l.

full load speed or, (2) it 1;he data is not available, perform an actual

~

motor starting t'e' sin wit'ra preland of 160 kVA on the. diesel generator.

~

- Y.

r and a terminal voltage of 480 V,(1.0 pu).

^

STARTING THE 100 hp FIRE PUMP - STA,NDET DIESEL GENERNTOR -

VF.

Starting the 100 hp fije pump using the.460 J, 312 kVA standby diesel

~

generator was examined with a preload of 160 kVA and the recommended operating terminal voltage of 483 V presented l'u Part IVC of this re-s a

po rt.. As can be seen in Table 7,.the motor' terminal voltage drops to 70% which is the minimum starting voltage rating of the motor. Thus, 4

the standby diesel generato-

, marginally idequit.e;;to start the 100 hp fire pump provided the diesel generator terminal volt, age is maintained at 483 V prior to starting the fire pump.

iV t

g,4

-l u?

jf l, I

'/

/

. /

c s

s W

I l

rp0182-0126a121-35 e.

'/v p

I

.~

1 37 REFERENCES i

1.

CP Co letter, K A Toner to K W Berry, " Big Rock Point Plant Adequacy of Statica Electric Distribution Voltages," August 14, 1981 2.

Response to Form 40 Request, F Turski, Big Rock Point to K E Yeager, October 30, 1981 3.

CP Co letter, C J Hartman/F Turski, Big Rock Point to D E Moggenberg, " Big-i Rock Point Plant - NUREG-0737, Item II.K.3.25, Effect of Loss of AC Power on hecirculating Pump Seals - Measured Loads for Emergency Diesel Genera-tor Following Loss of Station Power," March 20, 1981 4

4.

Stevenson, William D, Elements of Power Systems Analysis, McGraw-Hill Book Company, 1975, Pages 276-279 4

5.

Neuenswander, John R, Modern Power Systems, International Text Book Com-pany, 1971, Pages 126-129 1

6.

CP Co letter, P A Rusche/K E Yeager to K A Toner, " Recommended Tap Changes - Big Rock Point Plant," January 11, 1982 I

1 I

rp0182-0126a121-35 f'

i

e ATTACHMENT 2 OVERVOLTAGE (OV) AND UNDERVOLTAGE (UV) CONDITIONS 1

d 1.

With Offsite or Main Generator Power Available:

1.a)

With 250 KVA, WHSE, URS Voltage Regulator Out of Service *:

1.a.1)

UV at input of 460V motors, 480 V battery chargers and'I&C power supplies during plant base load operation when station auxiliaries are supplied by generator and generator is at minimum voltage.

'.2.2)

UV at input of 460V motors, 440V motors, I&C power supplies, 480V battery chargers and motor control center contactors during LOCA when station auxiliaries are supplied by 138 KV feed and 138KV feed is at minimum voltage 1.a.3)

UV at input of 480V battery chargers and certain I&C power supplies when plant is in cold shutdown and station auxiliaries

]

are supplied by 158KV feed and 138KV feed is at minimum voltage.

1.b)

With 250 KVA, WHSE, URS Voltage Regulator in Service *:

1.b.1)

UV at input of 460V motors, I&C power supplies, 480V battery chargers and motor control center contactors during LOCA when station auxiliaries are supplied by 138KV feed and 138KV feed is at a minimum voltage.

1.b.2)

UV at input of I&C power supply during LOCA when station auxiliaries are supplied by 46KV feed s.,d 46KV feed is at minimum voltage.

2.

Without Offsite or Main Generator Power Available:

2.a)

Emergency Diesel Generator Operating:

2.a.1)

OV at input of 440V motors with diesel terminal voltage at maximum.**

2.a.2)

UV at input to electric fire pump when pump is started and supplied by the emergency diesel which is preloaded to 160KVA.***

2.b)

Standby Diesel Generator Operating **:

2.b.1)

OV at input of 440V motors with diesel terminal voltage at maximum.

4 2.b.2 UV at input of I&C power supplies and 480V battery chargers with diesel terminal voltage at minimum.

t Refer to Table 3 of Attachment 1 Refer to Page 31 of Attachment 1 Refer to Page 35 of Attachment I nu0582-0013d142

l ATTACHMENT 3 PRELIMINARY RECOMMENDATIONS OV or UV Condition Eliminated (from Attachment II) a) Change main transformer tap from the 145/13.5KV ~

tap to'tne 140/13.5KV tap.

b) Change the No 11 station power transformer tap

,1. a.1, pa rt o f 1. a. 2*

from the 2400/480V tap to the 2340/480 tap.

1.a.3, 1.b.1 and 1.b.2 c) Change the No 22 station power transformer tap from the 2400/480 tap to the 2340/480 tap.

d) Maintain plant in cold shutdown when the remainder of 1.a.2*

voltage regulator is out of service.

e) Operate the emergency diesel generator at a 2.a.1 terminal voltage of 480V during maximum and minimum loading, f) Operate the standby diesel generator at a 2.b.1 and 2.b.2 terminal voltage of 483V during maximum and minimum loading.

g) Obtain additional fire pump / motor data to verify that the emergency diesel generator, when.preloaded to 160 KVA, is capable of starting and accelerating the fire pump or 2.a.2 h)

Perform field test to verify that the emergency diesel can start and accelcrate the fire pump when the diesel is preloaded to 160KVA at a terminal voltage of 480V.

' Refer to Table 3 of Attachment I nu0582-0013gl42

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