ML17262A566

LER 91-006-00:on 910629,EDG a Started Automatically Due to Apparent Undervoltage Signal from Bus 14 Undervoltage Monitoring Sys.Root Cause Not Determined.Bus 14 Energized & EDG Declared operable.W/910729 Ltr

ML17262A566
Person / Time
Site:	Ginna
Issue date:	07/29/1991
From:	Backus W, Mecredy R ROCHESTER GAS & ELECTRIC CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-91-006, LER-91-6, NUDOCS 9108050066
Download: ML17262A566 (16)

Text

ACCELERATED DISTRIBUTION DEMON TION SYSTEM

~0 REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9108050066 DOC.DATE: 91/07/29 NOTARIZED:, NO DOCKET FACIL:50-244 Robert Emmet Ginna Nuclear Plant, Unit 1,, Rochester G 05000244 AUTH. NAME AUTHOR AFFILIATION.

BACKUS,W.H. Rochester Gas & Electric Corp.

MECREDY,R.C.

RECIP.NAME

'ochester Gas & Electric Corp.

RECIPIENT AFFILIATION II

SUBJECT:

LER 91-006-00:on 910629,EDG A started automatically due to apparent undervoltage signal from Bus 14 undervoltage monitoring sys.Root cause not determined.Bus 14 energized & D EDG declared operable.W/910729 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ! ENCL I SIZE: 7 TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES:License Exp date in accordance with 10CFR2,2.109(9/19/72). 05000244 A RECIPIENT COPIES D RECIPIENT ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD1-3 LA 1 1 PD1-3 PD 1 1 D JOHNSON,A 1 1 INTERNAL: ACNW 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DET/ECMB 9H 1 NRR/DLPQ/LHFB10 1 1

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ROCHESTER GAS AND ELECTRIC CORPORATION 89 EAST AVENUE, ROCHESTER N.K 14649-0001 i

ROSERTC h1ECREDY TELEPHONE Vice President AAEACODETIB546 2700 Ctnna Nucfear Prnducticrn July 29, 1991 I

U.S. Nuclear Regulatory Commission Document Control Desk Washington,- DC 20555

Subject:

LER 91-006, Apparent Voltage Drop on Safeguards 480 Volt Bus 14 Causes an Automatic Start of the "A" Emergency Diesel Generator R.E. Ginna Nuclear Power Plant Docket No. 50-244 In accordance with 10 CFR 50.73, Licensee Event Report System, item (a)(2)(iv), which requires a report of, "any event or condition that resulted in manual or automatic actuation of any Engineered Safety Feature (ESF), "including the Reactor Protection System (RPS)", the attached Licensee Event Report LER 91-006 is hereby submitted.

This event has in no way affected the public's health and safety.

Very truly yours, Robert C. Mecr dy xc U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406 Ginna USNRC Senior Resident Inspector 9 i 080s00g,(,

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<<ACTAAcT IL<<evl s 1)00 eoas, I eeooeoeeev>>I) III>>oe e<<etvvoeee Itoeeee>>I>>o <<esl 114 On June 29, 1991 at 1754 EST with the reactor at approximately 98% full power, the "A" Emergency Diesel Generator started automatically due to an apparent undervoltage signal from the Bus 14 Undervoltage Monitoring System.

The "A" Emergency Diesel Generator, after starting, attained proper voltage and frequency. By design, Bus 14 because Bus 14 was at its proper voltage and being fed it did not close into from its normal power supply.

Immediate operator action was to verify that Bus 14 was energized and that the "A" Emergency Diesel Generator was operating normally.

Subsequently) the "A" Emergency Diesel Generator was stopped and realigned for auto-standby.

The cause of the event has . not been positively determined, although off-site electrical disturbance is postulated.

Since the cause of this event has not been positively determined at this time, we will continue to investigate for the underlying cause. Any further corrective action will depend on the re'suits of this investigation.

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L'ICENSEE EVENT REPORT ILERI TEXT CONTINUATION AFFHOVEO OMd HO 5150M(04 3

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PRE-EVE2iT PLANT CONDITIONS The plant was at approximately 984 steady state with no'ajor activities in progress.

full power II. DESCRIPTION OF %TENT A. DATES AND APPROXIMATE TIMES OP MAJOR OCCURRENCES:

0 June 29, 1991, 1754 EDST: Event Date and Time h

0 June 29, 1991, 1754 EDST: Discovery Date and Time 0 June 29, 1991, 2013 EDST: "A" Emergency Diesel Generator stopped and realigned for Auto-standby B. EVENT:

On June 29, 1991 at 1754 EDST, with the reactor at approximately 98% full power, the Control Room received the following alarms: L-14 (Bus 14.

Undervoltage Safeguards) and J-24 (Emergency Diesel Gen 1A Panel). The Control Room operators immediately verified proper voltage on Bus 14 and that the normal power supply breaker was closed. The Control Room operators also verified that the "A" Emergency Diesel Generator had started and displayed proper voltage and frequency. By design, the "A" Emergency Diesel Generator did not close into Bus, 14, as the bus voltage was normal and Bus 14 was still being supplied by its normal power supply.

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~0 ~e (042 I U.S. NUCLEAR REQVLATORY COMMI55ION L'ICENSEE EVENT REPORT ILERI TEXT CONTINUATION J ASSROVEO OM9 NO SISOWI04 EXSIRES, 9121/99 SACILITY NAME 111 OOCKET NVMEER 121 LER NVMQEII 191 SAOE l21 55QUENTIAL REVISION NUM NUM R.E. Ginna Nuclear Power Plant o2 44, 006 00 03pF 0 6 TEXT IIJ ~ <<>>5 ~ N ~. v>> NAS55JNJ HRC FOnn 2OEA'5I I ITI o 5 o o Subsequently, Auxiliary operators were dispatched to check the Bus 14 Undervoltage Monitoring System cabinets and the operation of the "A" Emergency Diesel Generator. The operation of the "A" Emergency Diesel Generator was found to be normal. No undervoltage trip targets were observed on Bus 14 or Bus 18 (both these buses are fed by the "A" Emergency .Diesel Generator).

During this event, routine activities were occurring at off-site Station 204. At approximately the same time as the apparent undervoltage condition occurred on Bus 14, a 34.5 kv capacitor bank was being removed from service. This is a routine action to correct off-site voltage situations. Station 204 'eeds Circuit 751, which was the normal off-site power supply to Buses 14 and 18.

Control Room operators notified higher supervision

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and the Nuclear Regulatory Commission of the event.

To prove operability of the Undervoltage Monitoring System, the Results and Test (R&T) Department performed Periodic Test procedure PT-9. 1 (Undervoltage Protection 480 Volt Safeguards Busses) on Bus 14. After PT-9.1

.was successfully completed, the "A" Emergency Diesel Generator was stopped and realigned for Auto-standby.

C. INOPERABLE STRUC'HIRES, COMPONENTS s OR SYSTEMS THAT CONTRIBUTED TO THE EVENT:

None.

D. OTEGsR SYSTEMS OR SECONDARY PUNCTIONS AFFECTED:

None.

E. METHOD OP DISCOVERY:

The events were immediately apparent due to alarms and indications in the Control Room.

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~e V,S. <<UCLEAII IlfOULATOIIYCOMMISSIOII L'ICENSEE EVENT REPORT (LER) TEXT CONTINUATION I ASSAOYEO OMS HO 3150MIOI EXSIAES, SISI l95 SACILITY NAME Ill OOCKET IIUMSEII 11I LEII <<UMSEII ISI ~ AOS ISI 5 ~ 4UC<<VIAL HUM << '" 'S<<UMV<<ION f<<

R.E. Ginna Nuclear Power Plant o s o o o 2 4 9- 1 0 06 00 0 4 o~0 6 TEXT illnave <<WCe <<nquseC vAS OdakevW lYPC Arm ~'ll I ITI F. OPERATOR ACTXON:

Following the Bus 14 Undervoltage Alarm and the "A" Emergency Diesel Generator automatic start, the Co'ntrol Room operators immediately verified proper voltage on Bus 14 via the normal power supply and

',that the "A" Emergency Diesel Generator displayed proper voltage and frequency.

Subsequently, Auxiliary operators were dis'patched to check -the Bus 14 undervoltage monitoring system and "A" Emergency Diesel Generator operation. The "A" Emergency Diesel Generator operation was normal and

,no undervoltage trip targets were observed on Bus 14 or Bus 18.

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The "A" Emergency Diesel Generator was subsequently stopped and realigned for Auto-standby.

G. SAFETX SXSTEM RESPONSES:

The "A" Emergency Diesel Generator automatically started and displayed proper voltage and frequency.

'IXI. CAUSE OF EV19Fl'.

XMM1sDIATE CAUSE:

The automatic actuation of the -"A" Emergency Diesel Generator was due to an apparent undervoltage signal from the Bus 14 undervoltage monitoring system.

B. ROOT CAUSE:

The underlying, cause of the apparent undervoltage signal from the Bus 14 undervoltage monitoring system is not positively determined at this time..

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ASSAOVEO OME IVO 1150MIOe EXSIAES, 4151/45 SACILITY IIAME Ill COCKET IvUMEEA 111 LEII IIUMEEA 141 SAOE IEI vEAA 5 4 0 0 4 VV T I A L ntvlelOM

~ VUM VVVM R.E. Ginna Nuclear Pawer Plant TExT lllnave Mece a eevveevL vvM vneeeval vYAC Sevvn SELA Yl I ITI osooo244 0 0 6 0 0 0 50F 06 IV. ANALYSIS OF EVENT The event is reportable in accordance with 10 CFR 50.73, Licensee Event Report System, item (a)(2)(iv), which requires 'eporting of, "any event or condition that resulted in manual or automatic actuation of any Engineered Safety Feature (ESF) including the Reactor .Protection System (RPS)". The starting of the "A" Emergency Diesel Generator was an automatic actuation of an ESF system.

An assessment was performed considering both the safety consequences and implications of this event with the following results and conclusions:

There were no operational or safety consequences or implications attributed to the starting of the "A" Emergency Diesel Generator because:

0 The "A" Emergency Diesel Generator operated as designed.

o Both Bus 14 power supplies (i.e. normal and emergency) were either in use or available throughout the event.

o The Bus 14 undervoltage monitoring system operation was in the conservative direction, (i.e. the operation actuated the automatic start of the "A" Emergency Diesel Generator).

Based on the above, it health and safety was assured at all times.

can be concluded that the public's V. CORRECTIVE ACTION A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:

o The R&T Department successfully completed PT-9.1 on Bus 14 and the "A" Emergency Diesel Generator was stopped and aligned for Auto-standby.

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FACILITY NAME III OOCIIET NVMEEII IEI LEII NVMEEII IEI ~ ACE ISI YEAA IEQVEHTIAL AEV ISIO<

4 M IA NVM IA R.E. Ginna Nuclear Power Plant TEIL illmort apece e mewaf. wt aAkenV HAC Fiwn DELI'IlI I Tl o s o o o. 24 4 9 1 006 0 006'F 0 6 B. ACTXON TAKEN OR PLANNED TO PREVENT RECURRENCE:

0 As the underlying cause of the event has not been determined at this time, investigations will continue to positively determine the underlying cause of this event. Any further corrective actions will depend on the results of these investigations.

0 Electrical system monitoring records have been reviewed, and indicate that removal of the capacitor bank resulted in a small and routine voltage transient.

0 Electrical system monitoring has been increased on Circuit 751.

0 The interface between the undervoltage monitoring system and diesel start circuitry will continue to be evaluated,'to determine if the undervoltage system is reacting as designed for small voltage fluctuations.

ADDXTXONAL XNFORMATION A. PAXLED COMPONENTS:

None.

B. PREVXOUS LERs ON SIMILAR EVENTS:

A similar LER event historical search was conducted with the following results: No documentation of similar LER events with an undetermined root cause at Ginna Station could be identified.

C. SPECIAL COMMENTS None.

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