ML17262B154

LER 92-007-00:on 921224,turbine Runback Occurred & a EDG Started & Tied Into Safeguard Buses 14 & 18.Caused by Loss of Power to Safeguards.Restored Normal Power to Safeguards Buses 14 & 18.W/930125 Ltr

ML17262B154
Person / Time
Site:	Ginna
Issue date:	01/25/1993
From:	Backus W, Mecredy R ROCHESTER GAS & ELECTRIC CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-92-007, LER-92-7, NUDOCS 9302030096
Download: ML17262B154 (24)

Text

ACCELERAD DOCUMENT DIST BUTION SYSTEM REGULATORY INFORMATION DISTRIBUTIO SYSTEM (RIDS)

ACCESSION NBR:9302030096 DOC.DATE: 93/01/25 NOTARIZED: NO DOCKET ¹ FACIL:50-244 Robert Emmet Ginna Nuclear Plant, Unit 1, Rochester G 05000244 AUTH. NAME AUTHOR AFFILIATION BACKUSiW.H. Rochester Gas & Electric Corp.

MECREDY,R.C. Rochester Gas & Electric Corp.

RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 92-007-00:on 921224,turbine runback occurred & "A" EDG started & tied into safeguard buses 14 & 18.Caused by loss D' of power to safeguards.Restored normal power to safeguards buses 14 & 18.W/930125 ltr.

DZSTRZBUTZON CODE: ZE22T COPZES RECEZVED:LTR ( ENCL ( SZZE:

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 Ai RECIPIENT COPIES RECIPIENT COPIES D ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCQ-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/EMEB 7E 1 1 NRR/DLPQ/LHFB10 1 1 NRR/DLPQ/LPEB10 1 1 NRR/DOEA/OEAB 1 1 NRR/DREP/PRPB11 2 2 NRR/DST/SELB 8D 1 1 NRR/DST/SICB8H3 1 1 RR T/S SB8D1 1 1 NRR/DST/SRXB 8E 1 1 REG FILE 02 1 1 RES/DSIR/EIB 1 1 RGN1 FILE 01 1 1 EXTERNAL 'G&G BRYCE i J H 2 2 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHY,G.A 1 1 NSIC POOREgW. 1 1 NUDOCS FULL TXT 1 1

/v N s 7(7$

D D

NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE( CONTACT THE DOCUMENT CONTROL DESK, ROOM PI-37 (EXT. 504-2065) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 29 ENCL 29

N$ b V 5 ~ ~ I~ 4 Jhf /I'ii

/ 'lOtC j 5Ts'lt I

ROCHESTER GAS AND ELECTRIC CORPORATION ~ 89 EAST AVENUE, ROCHESTER, N.Y. 14649-0001 546.2700 7CLCPnOhf,'+cA cooE 715 January 25, 1993 U.S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Subject:

LER 92-007, Loss of Offsite Power Circuit 751,~ Due To Wind Storm Induced Debris, Causes Automatic Actuation of An ESF and RPS System (i.e. Emergency Diesel Generator Operation and Turbine Runback)

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 92-007 is hereby submitted.

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

Very truly yours, Robert C. Mecre xco U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of- Prussia, PA 19406 Ginna USNRC Senior Resident Inspector

~()P 9302030096.930i25 PDR ADOCK 05000244 PDR

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (64) 9) APPROVED 0MB NO. 31504104 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPI.Y WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD LICENSEE EVENT REPORT ILER) COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (Pyr30), V.S. NUCLEAR REGULATORY COMMISSION. WASHINGTON. DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (31500104), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON. DC 20503.

FACILITY NAME (11 DOCKET NVMBER (2) PA E 3 R.E. Ginna Nuclear Power Plant 0500024410F10 Loss of Offsite Power Circuit 751, Due To Hind Storm I'nduced Debris, Causes 'Automatic EVENT DATE (5) LER NUMBER (6) OTHER FACILITIES INVOLVED (6)

MONTH DAY YEAR YEAR ~ SEQUENTIAL NSi NUMBER REVtSION MO~'

REPORT DATE (7)

DAY YEAR FACILITYNAMES DOCKET NUMBERISI 0 5 0 0 0 1 2' 4 0 7 0 5 0 0 0

' THIS REPORT IS SUBMITTED PURSUANT T 0 THE REQUIREMENTS OF 10 CF R ('I t IChrch onr or more of thr followinPl (11 OPERATING MODE (9) 20.402(b) 20.405(cl 50,7 3 ( ~ I (2)(le) '3.7((b)

POWER 20 406N)(1)IB 60.36(c) (1) 60,73( ~ )(2)(e) 73.71(c)

LEVEL (10) 20.405(sl(1)(6) 60.36(c) (2) 60,73(s)(2) (r9) OTHER ISprcify in Abstract below end In Feet, HRC Form 20.405(s) ((l(iiil 60.73( ~ I (2)(i) 60.73( ~ ) (2)(eII0(A) 3BSAI 20.405(s) (I )(IY) 60.73( ~ l(2)(iil 50,73 (s) (2) (yiii)(6) 20.406 (~ l (I)(s) 50.73(el(2) (iii) 50.'73( ~ )(2)(s) .

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER Wesley H. Backus AREA CODE Technical Assistant to the Operations Manager 31 552 4- 444 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE OESCRIBEO IN THIS REPORT (13)

MANUFAC. REPORTABLE MANUFAC EPORTABLE CAUSE SYSTEM 'COMPONENT TVRER TO NPRDS 54ISY@ CAUSE SYSTEM COMPONENT TURER TO NPRDS X E A CON X 9 9 SUPPLEMENTAL REPORT EXPECTED (141 MONTH DAY YEAR EXPECTED SUBMISSION DATE'151 YES III yet. complrtr EXPECTED SUBAIISSIOH DATEI NO ABsTRAcT I(imlt to f400 spree 5 I.r., epproelmrtr(y flftrrn tlnplr spree typrwriNrn linni (16)

On December 24, 1992, at 0435 EST, with the reactor at approxi-mately 984-steady state full power, a turbine runback occurred and the "A" Emergency Diesel Generator started and tied into safeguard buses 14 and 18.

The Control Room operators performed the appropriate actions of AP-TURB.2 (Automatic Turbine Runback) and verified that the "A" Emergency Diesel Generator was operating properly and that ,

safeguards buses 14 and 18 were'nergized. . The plant was sub-sequently stabilized at approximately 774 full power.

The cause of the event was the loss of power to safeguards buses 14 and 18 due to loss of offsite power 34.'5 KV Circuit 751. The underlying cause for the loss of Circuit 751 was determined to be windstorm induced debris intercepting the shield wire and phase conductor causing .a fault. (This event is NUREG-1022 (C) Cause Code) .

Corrective action was to restore normal power to safeguards- buses 14 and 18 from offsite power source 34.5 KV Circuit 767 and to stop the "A" Emergency Diesel Generator and realign -it for auto standby.

NRC Form 366 (64)9)

NRC FORM 368A U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 31500104 (689)

EXPIRES: 4/30/92 ESTIMATED 8)/ADEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REQUEST: 500 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH IP430), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO 1NE PAPERWORK REDUCTION PROJECT (31500104), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR rice SEQUENTIAL NUM 4 4 g~ REVISION NVMSE4 R.E. (rinna Nuclear Power Plant 0 5 0 0 0 24 492 0 0 7 0 0 02 o" 10 TEXT /ffmoro g>>co /4 rtufrorf, u>> I/Rrur'>>f HRC Form 35649/ ()2)

PRE-EVENT PLANT CONDIT ONS The plant was at approximately 98% steady state power with no major operational activities in progress.

The offsite power configuration to the plant was as follows:

o Offsite power 34.5 KV Circuit 751 was feeding the "ALI train safeguards buses 14 and 18 through 12A 34.5 KV/4160V transformer and through the safeguards buses 4160V/480V transformers.

o Offsite power 34.5 KV Circuit 767 was feeding the "B" train safeguards buses 16 and 17 through 12B 34.5 KV/4160V transformer and through the safeguards buses 4160V/480V transformers.

-The weather conditions in the area were high winds, blowing snow, and subfreezing temperatures.

DESCRIPTION OP EVENT A. DATES AND APPROXIMATE TIMES OP MAZOR OCCURRENCES 0 December 24, 1992, 0435 EST: Event date and time 0 December 24, 1992, 0435 EST: Discovery date and time 0 December 24, 1992, 0435 EST: Control Room operators verify the "A"'mergency Diesel Generator (D/G) Operation and safeguards buses 14 and 18 energized.

December 24, 1992, 0436 EST: Control Room operators perform the appropriate actions of abnormal procedure AP-TURB.2 (Automatic Turbine Runback) and stabilize the plant.

0 December 24, 1992, 0501 EST: Safeguard buses 14 and 18 resupplied from offsite power 34.5 KV Circuit 767.

NR C Form 368A (689)

NAC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (669) APPROVED OMB NO.3150410E E X PI A ES: 6/30/92 ESTIMATED BURDEN PEA RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFOAMATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (PJ)30). U.S. NUCLEAR, REGULATORY COMMISSION. WASHINGTON, OC 20555, AND TO 1'HE PAPERWORK REDUCTION PROJECT (31500104). OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON. DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

">

Nk'I SEOVENTIAL REVISION RE YEAR ~

NVMSER NVM ER R.E. Gonna Nuclear TEXT /// IIKVS Sg>>Ct /S PNJV/RR/ uW ~ PDT9er Plant NRC Fee@ 36SAB/ (17) 050'0024492 007 0 0 0 3 QF 1 0 o

• December 24, 1992, 0510 EST: The <<A<< Emergency D/G was stopped and realigned for auto standby.

o December 28, 1992, 0920 EST: Offsite power 34.5 KV Circuit 751 declared operable.

B. EVENT:

On December 24, 1992, at 0435 EST, with the reactor at approximately 984 steady state full power, the Control Room received numerous annunciator alarms.

The Control Room operators immediately determined that the following events had occurred:

o Safeguards buses 14 and 18 had lost their normal power supply. E 0 A turbine runback of approximately 204 full power had occurred.

0 The <<A<< Emergency D/G had started and was tied to safeguards buses 14,and 18.

The Control Room operators immediately performed the appropriate actions of AP-TURB.2 (Automatic Turbine Runback), transitioned to AP-ELEC.1 (Loss of 12A And/Or 12B Transformer) and verified that the <<A<<

Emergency D/G was operating properly and that safe-guards buses 14 and 18 were energized. The plant was subsequently stabilized at approximately 774 full power. The Control Room operators observed that 4160V bus 12A and offsite power 34.5 KV Circuit 751 displayed zero (0) voltage. The Control Room operators performed the appropriate actions of AP-,ELEC.l and contacted Power Control. The Power Control Dispatcher informed them that offsite power 34.5 KV Circuit 751 had tripped at, substation 204.

~ NRC Foe> 366A (669)

NRC FORM 366A (6 J)9) t LICENSEE EVENT REPORT ILER)

TEXT CONTINUATION U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3(500104 E XP I R ES: O/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 500 HRS. FORWARD COMMENTS REGARDING BUADEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P430). U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (31500104). OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, 00 20503.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE IS)

$ N: SEQUENTIAL Ngi'EVISION YEAR NUM ER 44 NUM ER R.E. Ginna Nuclear Power Plant TEXT ///mare r/IOOO/O r/O/ver/ IIOO ///OrrO/HRC FOrrrr 36//rEB/ I)7) 050002gg9 00 7 00 0 OF Subsequently, at 0452 EST, the Control Room operators, using Equipment Restoration procedure ER-ELEC.1 (Restoration of Offsite Power) energized 4160V Bus 12A from offsite power 34.5 KV Circuit. 767. At 0501 EST safeguard buses 14 and 18 were resupplied by offsite power.

At 0510 EST, December 24, 1992, the "A" Emergency D/G was stopped and realigned for auto standby.

At 0920 EST, December 28, 1992, after offsite power 34.5 KV Circuit 751 had been cleared for use, normal offsite power from Circuit 751 was made available to the plant. The current operating alignment utilizing 34.5 KV Circuit 767 is being maintained to supply the

'safeguards trains. Offsite power 34.5 KV Circuit 751 was maintained as the plant's backup supply of offsite power.

C INOPERABLE STRUCTURESP COMPONENTS, OR SYSTEMS THAT CONTRIBUTED TO THE EVENT:

None.

D. OTEGPR SYSTEMS OR SECONDARY FUNCTIONS AFFECTED:

None.

E. METHOD OF DISCOVERY:

The event was immediately apparent due to alarms and indications in the Control Room.

NAG Form 366A (649)

'

NRC FOAM 366A UA. NUCLEAR REGULATORY COMMISSION (64)9) APPROVED OMB NO. 31500104 E XP I R ES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT ILER) INFORMATION COLLECTION REQUEST: 500 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (P.530), U.S, NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3(500(04), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503, FACILITY NAME n) DOCKET NUMBER (2) LFR NUMBER (6) PAGE IS)

YEAR @R SEQUENTIAL NUM ER j~J

..A REVISION NUM ER R.E. Gonna Nuclear Power Plant o s o o o 244 92 00 7 000 5 OF 1 0 TEXT /// mare 4/race Et tertu/red, u>> add/r/arre/NRC Farm 36649/ ((7)

OPERATOR ACTION:

Following the turbine runback, buses 14 and 18 under-voltage, and the "A" Emergency D/G automatic start, the Control Room operators immediately performed the appropriate actions of AP-TURB.2 (Automatic Turbine Runback) and verified that the "A" Emergency D/G was operating properly and that safeguards buses 14 and

18. were energized.

Subsequently, the Control Room operators restored normal power to bus 14 and 18 and stopped and realigned the "A" Emergency D/G for Auto standby.

SAFETY SYSTEM RESPONSES:

The "A" Emergency D/G automatically started, displayed proper voltage and frequency and closed into safeguards buses 14 and 18 to supply emergency power.

III. CAUSE OF EVENT A. IMMEDIATE CAUSE:

The automatic turbine runback was caused by a dropped rod signal from the Nuclear Instrument System (NIS) power range N-42 and/or from the Microprocessor Rod Position Indication (MRPI) System.1 The automatic actuation of the "A" Emergency D/G was due to undervoltage on safeguards buses 14 and 18.

NRC Farm 366A (64)9)

1 NRC FORM 366A US. NUCI.EAR AEGULATOAYCOMMISSION (689) APPROVED OMB NO. 31504106 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPOATS MANAGEMENT BRANCH (F430), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO 1HE PAPERWORK REDUCTION PROJECT (31500104), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (21 'LER NUMBER (6) PAGE (3)

YEAR SEQVENTIAL REVISION HVMllER '?49: NVMSEA R.E. Gonna Nuclear P016er Plant TEXT //! nxve HM>> ls /Poult, u>> sddhiond HRC Ann 366AB/ ()7) 050002gg92 007 0 0 0 6 OF 1 0 B. INTERMEDIATE CAUSES:

The dropped Rod signal from NIS power range N-.42 was due to the momentary loss of the "B" instrument bus which supplied power to N-42. The loss of bus was due to. the momentary loss of MCC-1C the'B!'nstrument which supplied power to the constant voltage trans-former for the "B" instrument bus..

The dropped rod signal from the MRPI System was due to the momentary loss of MCC-1K which supplied power to the MRPI System. The loss of MCC-1K was due to the momentary loss of MCC-1C which .supplied power to MCC-1K.

The loss of MCC-1C was due to the momentary loss of power to safeguards bus 14.

The loss of power to safeguards bus 14 was due to the loss of offsite power 34.5 KV Circuit 751.

The undervoltage on safeguards buses 14 and 18 was due to the loss of offsite power 34.5 KV Circuit 751.

C. ROOT CAUSE:

On January 15, 1993 34.5 KV Circuit 751 was patrolled using bucket trucks. At pole T-424 on Lake .Road a burned phase conductor was found.

Based on the above the underlying cause of the loss of offsite power 34.5 KV Circuit 751 was determined to be windstorm induced debris intercepting the shield wire and phase conductor causing a fault.

(Wind gusts of up to 33.5 mph)

NRC Form 366A (669)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (64)9) APPROVED OMB NO. 31500104 EXPIRES: 4/30)92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE. EVENT REPORT (LER) INFORMATION COLLECTION REQUEST: 505) HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (PS30), U.S. NUCLEAR REGULATORY COMMISSION. WASHINGTON, OC 20555, AND TO 1HE PAPERWORK REDUCTION PROJECT (31504104), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON. DC 20503.

FACILITY NAME (II DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR SEQUENTIAI. REVISION NUMSER NUM ER I

R.E. 'Ginna Nuclear Power Plant 0 5 0 0 0 2 4 4 9 007 0 0 0 7 " 1 0 TEXT illIROIP <<coo lo toquiod, uoo oddldonol HRC Foun 36SAS I (12),

IV. ANALYSIS OF WHFNT The event is reportable in accordance with 10 CFR 50.73, Licensee Event Report System, item (a)(2)(iv), which requires reporting of, "any event or condition 'hat resulted'in manual or automatic actuation of any Engineered Safety Feature (ESF) including the Reactor Protection System (RPS)", in that the automatic turbine runback was an automatic actuation of the RPS and the starting of the

""A" Emergency D/G 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:

o All reactor control and protection systems performed as designedt thus limiting the overall effects of the turbine runback transient.

o The "A" Emergency D/G operated as designed by starting and supplying emergency power to safeguards buses 14 and 18.

o Offsite power 34.5 KV Circuit 767 was still in operation supplying power to the "B" train safeguards buses and subsequently was lined up to also .supply power to the "A" train safeguards buses as permitted by plant technical specifications.

Based on the above, health and safety was assured at it can be concluded that all times.

the public(s

'I NRC Form 366A (64)9)

NRC FORM 366A UA. NUCLEAR REGULATORY COMMISSION

'(64) 9) ~ APPROVED OMB NO. 31504))04 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REOUESTI 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH IP4)30), U.S. NUCLEAR REGULATORY COMMISSION. WASHINGTON. DC 20555, AND TO 1HE PAPERWORK REDUCTION PROJECT (3)504))04). OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME ul DOCKET NUMBER 12) LER NUMBER IS) ~ PAGE IS)

YEAR SEOUENTIAL REVISION NUMSER NUM ER R. E. Ginna Nuclear Power .Plant 0 6 0 0 0 2 44 92 0 0 7 0 0 08oF 1 0 TEXT /I/more Eoece l) reovter/, v>> er/drT/one/HRC Form 3ÃA'4) 117)

V. CORRE IVE ACTION A. ACTION TAKEN TO M%URN AFFECTED SXSTEMS TO PRE-EV19lT NORMAL STATUS:

After the plant had been stabilized, safeguards buses 14 and 18 normal power supplies were restored via offsite power 34.5 KV Circuit 767 and the "A" Emergency D/G was stopped and aligned for auto standby.

Subsequently an extensive troubleshooting effort was undertaken to determine the root cause of offsite power 34.5 KV Circuit 751 tripping out at substation 204. This troubleshooting effort included the following:

o Performing a visual and instrument survey along the entire length of offsite power 34.5 KV Circuit 751 between the plant and substation 204

. to ascertain if there were any damaged insulators, tree limbs, or other debris on lines, or evidence of anything that had possibly fallen across the line and burned free. No abnormal conditions were detected.

0 Inspecting substation 204 for any abnormal conditions'i.e. breakers, wires, monitoring equipment, etc.). No abnormal conditions were detected, except a distance monitor did indicate a problem had occurred at a 'certain distance-from Station 204. This area -was checked out with no abnormal conditions detected.

NRC FonII 366A )669)

NRC FORM355A ILS. NUCLEAR REGULATORY COMMISSION APPRDYED 0MB No. 3150010e (SJ)B)

E XP I R ES: e/30/02 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT ILER) INFORMATION COLLECTION REOUESTI 508> HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (P430), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO 1HE PAPERWORK REDUCTION PROJECT (31504(04). OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, OC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER IS) PAGE (3)

YEAR seaveNTIAL;.y) RE VLs ION NIJMse II NVMSER R.E. Glnna Nuclear Power Plant TEXT ///mme rpoco /s roeIJPed, ooo ~ HRC FomI 3SSA'e/ (17)

'o s o o o 2 44 92 007 0 0 9 OF.l 0 o Placing a high potential test on Circuit 751*

(i.e. approximately 70 KV) to identify possible intermittent abnormal conditions. One abnormal condition was discovered on wire connecting links'of two phases of the Circuit. These links were found to have pinholes in the jacket covering. Rochester Gas and Electric Corporation (RG&E) Transmission and Distribution Department believes these pinholes were caused by the high potential test placed on the line. No correlation between the pinholes and the original initiating event could be drawn. The links were subsequently repaired and retested satisfactorily. No other abnormal conditions were detected.

o On December 28, 1992 at 0920 EST offsite power 34.5 KV Circuit 751 was declared operable and cleared for use.

ACTZON TAKEN OR PLANNED TO,PREVENT RECUMUDtCE As the underlying cause was determined to be windstorm induced debris intercepting the shield wire and phase conductor causing a fault, the following corrective action was taken to prevent recurrence:

0 Tree trimming efforts for 34.5 KV Circuit 751 were reviewed and additional trimming was completed as of January 11, 1993 at pole T-424 on Lake Road and T-25A and T-26A on Slocum Road.

The RG&E Transmission and Distribution Department will continue their practice of Aerial patrol of 34.5 KV Circuit 751 twice per year utilizing thermal imaging and visual assessment of encroachments and general line'ntegrity. Based on those assessments appropriate maintenance activities will be performed.

NRC FomI 355A (SJ)B)

NRC FORM 366A US. NUCLEAR REGULATORY COMMISSION (689) OMB NO. 31600104 EXPIRES: E/30/92 CONTINUATION'PPROVED LICENSEE EVENT REPORT (LER) ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLFCTION REOUEST: 600 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT AND REPORTS MANAGEMENT BRANCH IP430), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON. DC 20556, AND TO 1HE PAPERWORK REDUCTION PROJECT (3150410>>), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

VEARI,>PI SEQUENTIAL ~5i REVISION

'>A NUMBER NUMSER R.E. Gonna Nuclear Power Plant o s o o o 2 44 92 007 0 1 0 OF 1 0 TEXT /// more e/wc>> /e n /Ir/rerL e>> a//I/Oo>>/ HRC %%drIII SBSE3/ (12)

ADDITIONAL INFORMAT 0 A. FAILED COMPONENTS:

The wire connecting links are of unknown origin with

, no part number or model number.

B. PREVIOUS LERs ON SIMILAR EVENTS:

A similar LER event historical search was conducted with the following results: No documentation of similar LER events with the same root cause at Ginna Station could be identified.'owever, LER 91-002 was a similar event with a different root cause.

C SPECIAL COMMENTS:

None.

NRC FoIm 366A (669)

1