ML18009A292

LER 89-017-01 on 891009,generator & Main Power Transformer Phase Differential Relay Tripped Lockout Relay.Caused by Multiple Ground Faults.Design Changes & Repairs Being Conducted While Plant Performs refueling.W/891208 Ltr

ML18009A292
Person / Time
Site:	Harris
Issue date:	12/08/1989
From:	HOWE A J, RICHEY R B CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
HO-890135-(O), LER-89-017-01, LER-89-17-1, NUDOCS 8912130259
Download: ML18009A292 (10)

Text

ACCELERATED DI<UTION DEMON 4TION SYSI"EI'.4i REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)ACCESSION NBR:8912130259 DOC.DATE: 89/12/08 NOTARIZED:

NO FACIL:50-400 Shearon Harris Nuclear Power.Plant, Unit 1, Carolina AUTH.NAME.AUTHOR AFFILIATION HOWE,A.J.Carolina Power&Light Co.RICHEY,R.B.

Carolina Power&Light Co.RECIP.NAME RECIPIENT AFFILIATION DOCKET 05000400 05000400

SUBJECT:

LER 89-017-01 on 891009,electrical fault on main generator output bus causing plant trip&fire damage in turbine bldg.W/8 ltr.DISTRIBUTION CODE IE22T COPIES RECEIVED LTR ENCL SIZE TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.NOTES:Application for permit'enewal filed.RECIPIENT ID CODE/NAME PD2-1 LA BECKER,D COPIES LTTR ENCL 1 1 1 1 RECIPIENT ID CODE/NAME PD2-1 PD COPIES LTTR ENCL 1 1 INTERNAL: ACRS MICHELSON ACRS WYLIE AEOD/DS P/TPAB DEDRO NRR/DET/EMEB9H3 NRR/DLPQ/LHFB11 NRR/DOEA/OEAB11 NRR/DST/SELB 8D NRR/DST/SPLB8D1 NUDOCS-ABSTRACT RES/DSIR/EIB 1 1 ACRS MOELLER 1 1 AEOD/DOA 1 1 AEOD/ROAB/DSP 1 1 NRR/DET/ECMB 9H 1 1 NRR/DET/ESGB 8D 1.1 NRR/DLPQ/LPEB10 1 1 NRR/DREP/PRPB11 1 1.NRR/DST/SICB 7E 1 1 NRR/~DTJSRXB 8E 1 1 REG FIL~02 1 1 GN2~ILE 01 2 2 1~1 2 2 1 1 1 1.1 1 2 2 1 1 1 1 1 1 1 1 EXTERNAL: EG&G WILLIAMS,S LPDR NSIC MAYS,G NUDOCS FULL TXT 4 4 1 1 1 1 1 1 L ST LOBBY WARD NRC PDR NSIC MURPHY,G.A 1 1 1 1 1 1 NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTETH CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT.20079)TO ELIMINATE YOUR NAME FROM DISTRIBUTION LISIS FOR DOCUMENTS YOU DON'T NEEDl FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 38 ENCL 38 0 Carojjna Power&Ught Company P.O.Box 165~New Hill~N.C.27562 R.B.RlCHEY Manager Hanta Nuclear Project OEC 0 8 1989 File Number.SHF/10-13510C Letter Number.'0-890135 (0)U.S.Nuclear Regulatory Commission ATTN: NRC Document Control Desk Washington, DC 20555 SHEARON HARRIS NUCLEAR POWER PLANT UNIT 1 DOCKET NO.50-400 LICENSE NO.NPF-63 LICENSEE EVENT REPORT 89-017-01 Gentlemen'.

In accordance with Title 10 to the Code of Fedeial Regulations, the enclosed Licensee Event Report is submitted.

The original report.fulfilled the requirement for a written report'ithin thirty (30)days of a reportable occurrence and is in accordance with the format set forth in NUREG-1022, September 1983.This supplemental report provides final conclusions as to the cause of the event from the long term investigation.

RBR:djs Enclosure Very truly yours, cmH~~R.B.Richey, Manager Harris Nuclear Project cc: Mr.R.A.Becker (NRR)Mr.S.D.Ebneter (NRC-RII)Mr.J.E.Tedrow (NRC-SHNPP)8912130259 S91009 t='DR ADOCI<0=000400 PDC MEM/LER-017-01/1/OS1 NRC FORM 366 (649)U.S.NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT{LER)APPROVED OMB NO.31500104 EXPIRES'/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 500 HRS.FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P430), U.S.NUCLEAR REGULATORY COMMISSION.

WASHINGTON.

DC 20555, AND TO THE PAPERWORK REDUCTION PRO/ECT (31500104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, OC 20503.FACILITY NAME (1I SHEARON HARRIS NUCLEAR POWER PLANT DOCKET NUMBER l2)PA E 0 5 0 0 0 4 O O 1 OF O 8/VZkfRICAL FAULT ON HAIN GENERATOR OUTPUT BUS CAUSING PLANT TRIP AND FIRE DAMAGE IN EVENT DATE ISI LER NUMBER (6)REPORT DATE (7)OTHER FACILITIES INVOLVED ISI MONTH DAY YEAR YEAR ec'2 SEQUENTIAL NVMSER'A'xc RNvtsr0rs ISVMSER MONTH OAY YEAR FACILITY NAMES DOCKET NUMBER(S)0 5 0 0 0 1 2 8 9 0 5 0 0 0 OPERATING MODE (9)POWER LEVEL (10)THIS REPORT IS SUBMITTED PURSUANT 7 50.73(~)l2)(ivl 50.73(~l(2)hl 50.73(~)(2)(vN)20AOS(c)50.36(c)Ill 50.36(cl(2) 50.73(~l(2)(I)50,7 3(e I (2)IN)50.73(~)(2)IN(I 20A02(8)20A05(~)(1)IB 20A05(e)(1)

INI 20A05(~)(1)INI)20A05(e l(1)(N)20.i05(el(ll(vl 50,73N)(2)(vIII)(Al 50.7 3 I~)(2)(viN)(Bl 50,73 (e I (2)(el I.ICENSEE CONTACT FOR THIS LER 02I 0 THE REQUIREMENTS OF 10 CFR (I:/Check one or more ol the/ollow)np/

(11)73.71GII 73.71(cl QTHER/Speclly/n Atrstmct Oe/orv enrp/n Test, HI/C Forth 3SSAI NAME W.OW R.PECIALIST TELEPHONE NUMBER AREA CODE 91 9362-2 71 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (\3)CAUSE SYSTEM COMPONENT MANUFAC.TVRER*COMPONENT MANUFAC-TURER TO HPIIOS E L N/A C E X F M R W 1 2 0 N B E L C T W 1 2 0 N X B A T AC A12 3 Y Pc'c(SÃ%%:':

SUPPLEMENTAL REPORT EXPECTED (1i)YF 5 III yes, complete EXPECTED SI/Eht/SSIDH DATE/NO ASSTRACT/Limit to tc00 sprees, I e., epprovlmcrcry I/lreen s/npleepece typevrrltten lintel I)8)EXPECTED SU 8 MI SS ION DATE R6I MONTH DAY YEAR On October 9, 1989, at 2305, a generator and main power transformer phase differential relay tripped the lockout relay of the main generator, tripping the generator and cnusing a turbine nnd reactor trip from 1004 power.The reactor was stabilized in hot standby at 557'on auxiliary feedwater and condenser steam dumps.Actuation of the generator and main power transformer differential relay and subsequent generator trip was caused by multiple ground faults.The ground faults destroyed the neutral grounding bus and caused three fires: an oil fire at the<<B'r main power transformer, a hydrogen fire underneath the main generator and a third small oil fire in the generator housing.An alert was declared, and the site" fire brigade responded to the fires, assisted Inter by off site fire departments, All fires appeared out by 0145, and the emergency condition was terminated at 0245.The initiator of the ground faults has been identified as aluminum debris in the isolated phase bus duct, which was deposited in the bus duct from previous failures of the duct cooling system dampers.Arcing from the aluminum debris in the bus led to a double phase to ground fault at the<<B<<main power transformer, Magnetic forces from this fault broke insulators in r'A'r phase and<<B'1 phase of the isolated phase bus duct.The<<A<<phase conductor contacted the bus enclosure creating another ground fault, These faults elevated the voltage at the generator neutral and led to another ground fault in the neutral grounding transformer cubicle, The turbine-driven auxiliary feedwater pump started after the reactor trip, but the pump tripped shortly thereafter', The cause of the trip is believed to be n spurious overspeed trip signal from the tachometer.

Design changes nnd repairs are being conducted while the plant conducts a refueling outage.NRC Form 366 (669)

,NRC FORM 366A 1649)i U.S.NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT ILER)TEXT CONTINUATION t APPROVED OMB NO.31500104 EXPIRES: 4/30/92 ESTIMATED BUADEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 500 HRS.FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH IP430), U.S.NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO 1HE PAPERWORK REDUCTION PROJECT 13150d104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.FACILITY NAME I'I)DOCKET NUMBER (2)LER NUMBER PS)PAGE 13)SHEARON HARRIS NUCLEAR POWER PLANT TEXT/I/mare 4/rece/4>>qu/rer/

u>>eddIo'onal HRC Farm Sr/MS/117)INITIAL CONDITIONS:

o s o o o 4 00 YEAR@c'.sEQUENTIAL Qa NUMSSR 017 REVISION NUMSSR 0 102 OF 0 8 The plant was operating at 100X power, 885 MWe net, on October 9, 1989.EVENT DESCRIPTION:

At 2305, a generator and main power transformer differential relay trip caused a generator lockout relay trip, which resulted in the following:

(1)the main generator output breakers and the generator exciter breaker tripped, (2)on-site power transferred from the unit auxiliary transformers to the startup transformers, and (3)the turbine tripped.A reactor trip directly occurred on the turbine trip, with all rods inserting into the core.Response to the trip was as expected;the main feedwater pumps tripped during the transient and the auxiliary feedwater (AFW)system actuated properly, the main steam isolation valves were manually closed to limit the cooldown.The turbine-driven AFW pump tripped shortly after it started, but the two 100X capacity motor-driven AFW pumps were available throughout the event.The turbine-driven AFW pump was capable of manual restart from the control room, but it was not needed during the event.At 2309, the Control Room received reports of two flashes having'ccurred, one at the"B" main power transformer, and the other on the second level of the turbine deck underneath the main generator.

The site fire brigade was activated, and brigade personnel reported fires at the"B" main power transformer, at the main generator housing on the top level of the turbine deck, and a hydrogen fire on the second level of the turbine deck underneath the main generator.

Off site fire departments were contacted to assist in the fire fighting efforts.At 2335, an alert was declared due to the release of flammable gas into the site protected area.At 2341, the state and local government emergency response officials were notified.Plant personnel were notified to activate the Technical Support Center (TSC).By 0013, the fire at the generator housing had been extinguished, the fire at the main power transformer was believed extinguished by actuation of the deluge system (a small oil fire was later determined to still be burning, and was extinguished using a dry chemical extinguisher), and the hydrogen fire underneath the generator was reported under control, with hydrogen to the main generator isolated.All visual flames at all three fire locations were extinguished by 0145.At 0245 when all fires were verified extinguished by walkdowns, fire watches were set, and the main generator was being purged with carbon dioxide, the alert was terminated.

NAC Form 366A)649)

,NRC FORM 368A (64)9)U.S.NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)TEXT CONTINUATION t APPROVED 0MB NO.31500104 E XP I R E S: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REOUESTI 50.0 HRS.FORWARDCOMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH IP4)30), U.S.NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (31504104).

OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.FACILITY NAME u)DOCKET NUMBER (2)YEAR LER NUMBER (6)SEOUENTIAL NUMBER j~j1~'EVISION

'o:PJ NUMBER PAGE (3)SHEARON HARRIS NUCLEAR POWER PLANT TEXT fit moro e>>oo ir roordrod.IIBB ddrS)lono//YRC Form 3554'4/(12)PLANT DBSIGM: o s o o o 4 o 017 0 1 0 3 pF0 8 The main generator is designed with the neutral of the wye grounded through a single phase transformer.

The secondary side of this transformer is connected to a high resistance network.With this design, a single phase fault to ground of the main generator output results in a small current flow through the neutral grounding transformer and its high resistance bank.A ground detection relay will actuate to isolate the fault by tripping the main generator, exciter field breaker and the generator output breakers.CAUSE: The initiator of the event was multiple ground faults in the"delta" section of the isolated phase bus duct near the"B" phase main power transformer.

Refer to Attachment A,"Physical Layout of SHNPP Generator Output." These ground faults were apparently caused by aluminum debris carried down the bus~duct.by the forced air cooling system.The'aluminum debris entered the bus duct as a result of previous damper failures in the bus duct cooling system.These failures occurred on February 27, 1988, and in the summer of 1989.Arcing between the conductor and the enclosure occurred over a fifty (50)foot length of the"A".phase, bus immediately upstream of the"B" main power transformer.

Ionization from this arcing reduced the dielectric strength of the cooling air, which,was carried into the bushing box of the HB" main power transformer.

-This caused an"A" phase',,to ground flashover in the bushing box, which, immediately propagated

'to.the.".B"'phase bushing.The fault cracked both low voltage bushings, causing oil to'leak from the bushings, and ignited the'eaking oil.The fault at the HB" main power transformer creat'ed magnetic forces in the main section of the isolated phase bus that broke insulators (Original Manufacturer:

Westinghouse; model 113C417A01, and 133C387A01; currently supplied by Delta Unibus)in"A" and"B" phase.The 23" diameter tubular conductor is suspended in the middle of the 41" diameter aluminum enclosure by the ceramic insulators.

In the"A" bus duct five insulators pulled apart, allowing the conductor to come in contact with the ,grounded enclosure, creating a phase-to-ground fault.The faults in the HB" main power transformer bushing box and the"A" bus duct elevated the voltage of the generator neutral.A curxent transformer used for the main generator radio frequency monitor (Manufacturer'.

Westinghouse; model 608D56G01) is mounted around the neutral conductor inside the neutral grounding transformer enclosure.

The current transformer, which is at ground potential, is insulated from the neutral conductor by insulating tape wrapped around the neutral conductor.

When the voltage of the neutral became elevated, this tape failed to provide adequate insulation, and the neutral.faulted to ground.Axcing in the area burned holes in generator moisture N R 0 Form 368A (64)9)

NRC FORM 366A'(64)9)U.S.NUCLEAR REGULATORY COMMISSION i LICENSEE EVENT REPORT HLER)TEXT CONTINUATION APPROVED OMB NO.3)504))04 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REOUESTI 50.0 HRS.FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS ANO REPORTS MANAGEMENT BRANCH (P4)30), U.S.NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555.AND TO THE PAPERWORK REDUCTION PROJECT (31504104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON.

DC 20503.FACILITY NAME (1)DOCKET NUMBER (2)LER NUMBER (6)YEAR@3 SEOUENTIAL gxQ'EVISION NUMSER.r>i NUMSER PAGE (3)SHEARON HARRIS NUCLEAR POWER PLANT TExT///more eoece/4 n/Ir/rerL Iree I//oooo/HAc Form 36EAB/(12)CAUSE (continued) o s o o o 4 o 8 9 Ol 7 Ol 0 40F 0 8 detector piping located above the neutral grounding transformer cubicle.Hydrogen escaping from the piping was ignited by the arcing.This subsequently ignited an oil fire in the main generator housing above.The ceramic-insulators in the duct which support the bus conductor are located underneath the bus directly supporting it until the bus duct leaves the turbine'deck, after which the arrangement is inverted, so that the bus is suspended from the insulators.

This is per design documents for all three bus ducts.Testing of the insulators removed from the bus duct confirmed their adequacy for this application.

The current transformer for the radio frequency monitor was a vendor supplied modification to the neutral grounding network, and was properly installed per design.The bus duct cooling system dampers wer'e apparently undersized for their application.

Replacement dampers will be of more substantial construction.

Prompt response by site personnel and the early decision to obtain off site assistance is credited in limiting the potential damage to plant equipment.

The damage to plant equipment was as follows: main generator:

neutral bushings and current transformers, external housing, and the exciter end seal oil piping, generator moisture detection piping'"B" main power transformer'.

bushings and connections to the isolated phase bus ducts"A" isolated phase bus duct neutral grounding transformer neutral grounding bus radio frequency monitor miscellaneous cabling and piping in the vicinity The cause of the TDAFW pump trip was investigated on the following day.A review of the data indicates no overspeed condition occurred when the pump*started.A test was performed to simultaneously start all three AFW pumps with steam generator pressure near the pressure existing immediately after the reactor trip', no overspeed trip occurred, and suction pressure on the header common to all three pumps did not decrease significantly.

NRC Form 366A (64)9)

NRC FORM 386A'(649)U.S.NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT ILER)TEXT CONTINUATION t APPROVEO OMB NO.31504(04 EXPIRES.1/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REOUESTI 50JI HRS.FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (F430).U.S.NUCLEAR REGULATORY COMMISSION, WASHINGTON, OC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3150410$), OFFICE OF MANAGEMENT AND BUDGET.WASHINGTON.

DC 20503.FACILITY NAME (1)SHEARON HARRIS NUCLEAR POWER PLANT TEXT/llrrrrrrE g>>ce/En/I/rrrrL IIJB///BBr>>JHRC%%dnn36643/(12)

CAUSE (continued)

DOCKET NUMBER (2)o s o o o 4 YEAR 8 9 LER NUMBER (8)EEOUENTIAL NUMBER 0 1 7 REvr$roN NUMBER 0 1 PAGE (3)0 5 OF 0 8 Based on recent experience during testing of the pump, it is believed that the tachometer (Manufacturer'.

Airpax', model 080-321-3X10) which actuates the electrical overspeed trip of the TDAFW pump may be providing spurious trip signals.The design of the tachometer provides two separate outputs, such that the channel experiencing spiking could trip the pump, while the other channel providing indication would show no malfunction..

SAFETY SIGNIFICANCE:

The plant response to the generator trip was as expected, wi.th the reactor stabilized in hot standby on AFW and condenser steam dumps.The unavailability of the TDAFW pump did not compromise safety since the motor-driven AFW pumps were available and operated throughout the event.The fires and the related damage were limited to the non-safety portions of the plant.No injuries occurred due to the fires.No previous fires within the protected area have occurred.Pr'eviously reported trips of the TDAFW pump had been attributed to moisture accumulation in the steam supply lines.Based on recent testing and data collection from this event, as well as the testing performed following this event, moisture accumulation is no longer believed to be the cause of the trips.The data shows that the actual speeds of the turbine may have exceeded the previous setpoint of the electrical overspeed trip in effect during previous events.The trip which occurred for this event was not an actual turbine overspeed as shown by the data.This event is reported under 10CFR 50.73(a)(2)(iv) as an actuation of engineered safety features, and under 10CFR 50.73(a)(2)(iv) due to the fire and release of hydrogen gas.CORRECTIVE ACTIONS: 1.The main power transformers were inspected and tested, and no significant damage, other than to the bushings and connections of the"B" transformer, was found.2.The generator has been fully tested and repairs are being made as necessary prior to generator restart.Inspections and testing have revealed no significant damage to the generator.

3.All other damaged components will be repaired prior to generator restart during the current refueling outage.NRC Form 388A (689)

NRC FORM 388A (6 J)9)i U.S.NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)TEXT CONTINUATION APPROVED 0MB NO,31500(oi EXPIRES: 8/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REOUEST: 50A)HRS.FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P830), U.S.NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO 1NE PAPERWORK REDUCTION PROJECT (3(500104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.FACILITY NAME (I)DOCKET NUMBER (2)LER NUMBER (8)yEAR~~@'EQVENTrAL

~'VSN NVMSErr J>~C NUMBErl PAGE (3)SHEARON HARRIS NUCLEAR POWER PLANT TEXT///moro<<>>co/r Jo//r'orL rrro or/r//bono/HRC

%%dnn 35543/(IT)CORRECTIVE ACTIONS (continued) o s o o o 4 00 89 0 17 0 1 06 QF 0 8 4.The design of the isolated phase bus duct bus supports has been evaluated and found to be adequate.However, the sections in which the conductor supports failed has been-rotated 180'o place the supports underneath the conductor as a prudent design measure.The damaged duct has been replaced.5.The design of the radio frequency monitor current transformer has been revised to ensure it'an withstand expected conditions under ground faults, and it will be replaced.6.The design of the isolated phase bus duct cooling system has been evaluated and revised to preclude debris intrusion into the ducts.7.The TDAFW pump tachometer electronic trip function was evaluated as unnecessary to protect against overspeed and its trip function will be deleted.ADDITIONAL INFORMATION ON EMERGENCY RESPONSE: This event was declared an alert by the Shift Foreman, and the Technical Support Center (TSC)was required to be activated.

Certain specific requirements for achieving augmentation of the plant staff detailed in the Emergency Plan were not met.In particular, the Accident Assessment Team and Damage Control Team are required to meet certain staffing levels at a 45 minute elapsed time and a 75 minute elapsed time, following activation.

Initial activation of the pagers for TSC members was delayed due to the pre-planned absence of the on shift clerk, who normally performs this duty.Alternative personnel were not as familiar with the pager procedures.

The Accident Assessment Team leader did not hear his pager, and additional time was spent to contact backup individuals.

The Damage Control Team leader did not contact additional personnel for the team prior to his reporting to the TSC.The following corrective actions will be taken to correct these deficiencies:

1.Additional training on pager activation will be provided to appropriate shift personnel.

2.Additional instructions will be given to all personnel carrying pagers who must in turn call additional personnel.

3.An unannounced augmentation drill will be conducted to verify the effectiveness of the above corrective actions.NRC Form 388A (M9)

NRC FORM 366A'(64)9)i U.S.NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)TEXT CONTINUATION APPROVED OMB NO.3(500104 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50A)HRS.FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P4)30), U.S.NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (31504)104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.FACILITY NAME Ol DOCKET NUMBER (2)YEAR LER NUMBER (6)SEQUENTIAL NUMBER REVISION NUMBER PAGE (31 SHEARON HARRIS NUCLEAR POWER PLANT TEXT ill mare<<reae/4 nrtu/rerL uee er///haarre/NRC Farm 35649/(IT)HZIS CODES: 0 s o o p 4 008 9 0 l 7 0 1 0 7 pF 0 8 Main Generator TB Generator Mater Detector Neutral Grounding Transformer TL EL:XFMR Radio Frequency Monitor Current Transformer EL:XCT Electrical Support Isolated Phase Bus Ducts Main Transformers EL:BDUC EL:XFMR Startup Transformers Unit Auxiliary Transformers Main Feedwater Auxiliary Feedwater TDAFW Pump Tachometer Main Steam Isolation Valves FK'XFMR FK:XFMR SJ BA BA TAC SJ:ISV NRC Farm 366A (669)

PHYSICAL LAYOUT OF SHNPP GENERATOR OUTPUT TURBINE FIRE ALSO IN GENERATOR HOUSING 6 GENERATOR EL.514'A'HASE BUS CCtmUCTOR CONTACTS DUCT, SHORTING.TO GROUND DEBRIS IS CARRIED D9ÃN BUS DUCT BY COOLING AIR FLOW CAUSING t1ULTIPLE GROUND FAULTS TOUAT's IONIZED AIR FROt1 DUCT FAULT SHORTS 8'RANSFORtIER CONNECTORS TO GROUND IGNITIHG ANOILFIRE 0 0 0 2 OOOO OOOO FAILURE OF PIPING FRO1 ARCING IGNITES HYDROGEN F IRE WDER GENERATOR CT IN NEUTRAL GROUNDING 4 TRANSFCRt1ER SHCRTS TO GROUND.GROLNDIHG NEUTRAL BUS AND INITIATING HIGH FAULT CURRENTS.NEUTRAL BUS BUS DUCT EL.286'EUTRAL GRCUNDING TRANSFORt1ER GROUND LEVEL EL 261'UPPORTS (TYPICAL)00 0 000 0 0 0 0 OOOO 000 HAIN TRANSFORMERS 00 IS 00 00 M I 0 O'4 Co I