ML17306B341

LER 93-003-00:on 930213,intermediate Bus Opened on Overcurrent,Resulting in Loss of Power to Train a Class 1E 4.16 Kv Bus.Caused by Fault on Supply Breaker for Switchyard Control.Supply Breaker Racked out.W/930313 Ltr

ML17306B341
Person / Time
Site:	Palo Verde
Issue date:	03/13/1993
From:	Bradish T, James M. Levine ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
192-00835-JML-T, 192-835-JML-T, LER-93-003, LER-93-3, NUDOCS 9303190225
Download: ML17306B341 (16)

Text

ACCEI ERATO DOCUMENT DIST > UTION SYSTEM REGULATO~INFORMATION DISTRIBUTION TEM (RIDS)

ACCESSION NBR:9303190225 DOC.DATE: 93/03/13 NOTARIZED: NO DOCKET g FACIL:STN-50-528 Palo Verde Nuclear Station, Unit 1, Arizona Publi 05000528 AUTH. NAME AUTHOR AFFILIATION BRADISH,T.R. Arizona Public Service Co. (formerly Arizona Nuclear Power LERVINE,J.M. Arizona Public Service Co. (formerly Arizona Nuclear Power RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 93-003-00:on 930213,determined that loss of power to Train A Class lE 4.16 kv Bus.Caused by overcurrent condition D on Intermediate Bus.Breaker for switchyard control power was removed.W/930313 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL SIZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES:STANDARDIZED PLANT 05000528 A

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD5 LA 1 1 PD5 PD 1 1 D

TRAMMELLgC 1 1 TRAN,L 1 1 INTERNAL: ACNW 2 2 ACRS 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DE/EELB 1 1 NRR/DE/EMEB 1 1 NRR/DORS/OEAB 1 1 NRR/DRCH/HHFBHE 1 1 NRR/DRCH/H ICB 1 1 NRR/DRCH/HOLB 1 1 NRR/DRZL/RPEB 1 1 NRR/DRSS/PRPB 2 2 NgR/DSSAJSPLB 1 1 NRR/DSSA/SRXB 1 1 4g'.G~KS 02 1 1 RES/DSZR/EIB 1 1 RGN5 FILE 01 1 1 EXTERNAL EG6tG BRYCE g J ~ H 2. 2 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHY,G.A 1 1 NSIC POORE,W. 1 1 NUDOCS FULL TXT 1 1 D

D NOTE TO ALL"RIDS" RECIPIENTS:

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

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FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 33 ENCL 33

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Arizona Pubhc Service Company PALO VERDE NUCLEAR GENERATING STATION P.O. BOX 52034 ~ PHOENIX. ARIZONA85072-2034 JAMES M LEVINE 192-00835-JML/TRB/RJR VICE I'RESIDENT NUCI.EAR PRODUCTION March 13, 1993 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Mail Station Pl-37 Washington, D.C. 20555

Dear Sirs:

Sub) ect: Palo Verde Nuclear Generating Station (PVNGS)

Unit 1 Docket No. STN 50-528 (License No. NPF-41)

Licensee Event Report 93-003-00 File: 93-020-404 Attached please find Licensee Event Report (LER) 93-003-00 prepared and submitted pursuant to 10CFR50.73. An automatic start of an Emergency Diesel Generator during a Loss of Power to the Train A Class lE 4.16kv bus. In accordance with 10CFR50.73(d), a copy of this LER is being forwarded to the Regional Administrator, NRC Region V.

If you have any questions, please contact T. R. Bradish, Nuclear Regulatory Affairs Manager, at (602) 393-5421.

Very truly yours, m/t ~4 JML/TRB/RJR/ap Attachment cc: W. F. Conway (all with attachment)

J. B. Martin J. A. Sloan INPO Records Center ZSOO50 S

9303i90225 9303i3 PDR ADOCK 05000528 PDR j"

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ig NRC Document Control Desk Licensee 'Event Report 1-93-003-00 Page 2 bcc: W. E. Ide 7194 R. K. 'Flood 7294 R. J. Adney 7394 R. F. Schaller 7194 T D. Shriver

~ 7294 J. J. Scott 7394 F. W. Riedel 7198

'.P. J. Wiley L. Clyde Source Document File 7298 7398 7747 CRDR File: i-3-t3071 R. J. Stevens '. ".

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7603

'.E. G. Firth C. Fullmer D. M. Eastman 6156 7996 7995 M. K. Muhs (STA) 7595

, T. E. Matlock (NSD) 1510 S. G. Penick (ISE) 7997 R. W. Page '1678 D. B. Andrews 6200 A. C. Rogers 1534 R. G. Hogstrom 7545 D. A. Hettick 7965 J D. Bayless

~ 7564 A. C. Gehr 4141 A. H. Gutterman P. J. Coffin 7636 B. A. Brown 7636'965 T. A. Buvens Dave Brevig Dennis Cox Responsible Departmen t (required review):

NRA Supervisor NRA Manager M. J. 'Reid 1'605 D. W. Smyers 7524 M. R. Oren 7516

ij LICENSEE EVENT REPORT (LER)

FACILITYNAME (I) DOCKET NUMBER (2) PACE 3 0 5 0 0 0 1 oF 0 TITLE (c)

Loss of Power o Trai A 01 s 1E 4.1 kV B EVENT DATE (6) LEB NUMBER (6) REPORT DATE P) OTHER FACfUBES INVOLVED(6)

I FACIUTY NAMES DOCKET NUMBER(S)

MONTH DAY YEAR YEAR NUMBER NUMBER MONTH DAY YEAR 0 5 0 0 0 0 2 1 3 9393 0 03 0 0 0 3 13 9 3 THIS REPORT IS SUBMIITEDPURSUANT TO THE BEOUIBEMEHTS OF 10 CFR Sf (Checlt one or moro of ote foscvrfno) (11) 0 5 0, 0 0 OPER ATINO MODE (0) 20A02(b) 20AOS(c) S0.73(a)(2) (tv) 73.71(b)

POWER 20 605(aXIK~) 5046(c)(1) 50.73(a)(2)(v) 73.71(c)

'LEVEL (10) 20AOS(a)(1~v 504 6{c)(2) 50.73(a)(2)(vs OTHER (Spectty In Abstract below end ln Text IVRC Form 20AOS(a)(1)(ns) 50.73(a) (2)(I) 50.73(a)(2)(m)(A) 366A) 20AOS(a)(1)(tv) 50.73(a)(2@i) 50.73(aX2)(vII)(B) 20AOS(a)(I)(v) 50 73(a) (2){E) 50.73(a)(2) (x)

'LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER Thomas R. Bradish, Nuclear Re ulatorv Affairs Manager COMPLETE ONE LINE FOR EACH COMPOHEHT FAILURE DESCRIBED IN THIS REPORT (13) 602393-5421 MANUFAC MANUFAC.

CAUSE SYSTEM COMPONENT TURER SYSTEM , COMPONENT TURER BUppLE MENTAL BEpo RT ExpEcTED (I4) MONTH DAY YEAR EXPECTED SUBMISSION DATE (16)

YES (tlyrs. complete EXPECTED SUBMISSION DATE)

ABSTRACT (f&tto ISOO spacea I e.. epproxlma tery Slteen ebvtle space typewrttten lsres) (I 6)

On February 13, 1993, at: approximately 0614 MST Palo Verde Unit 1 was in Mode 1 (POWER OPERATIONS), operating at approximately 100 percent power when the normal supply breaker to t'e Unit 1, non-Class 1E 13.8 kV, Int:ermediate Bus opened on overcurrent. This resulted in a loss of power to the Unit 1 Train A Class lE 4.16 kV bus. The Loss Of -Power Engineered Safety Feature (ESF) signal automatically load shed the Class 1E 4.16 kV bus and started the Train A Emergency Diesel Generator. All equipment functioned as designed, and no other ESF signals were actuated or required. Unit 1 continued to operate normally at 100 percent power. Units 2 and 3 were not affected by this event.

An initial inspection of the switchgear indicates that the normal supply breaker to the Intermediate Bus tripped on overcurrent. Troubleshooting identified damage on the C phase, line side to bus interface, of the normal supply breaker for switchyard control power. This caused the normal supply breaker for the Intermediate Bus to open on overcurrent as designed. A Root Cause of Failure Analysis is being conducted to determine the cause of overcurrent condition. The damaged line side to bus interface was removed the from the switchyard c'ontrol power switchgear and the Intermediate Bus was re-energized from its alternate supply. The Emergency Diesel Generator was shutdown at approximately 1617 MST on February 13, 1993.

No similar events have been previously reported pursuant to 10CFR50.73.

il LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITYNAME DOCKET NUMBER LER NUMBER PACE SEQUENTIAL REVISION NUMBER NUMBER Palo Verde Unit 1 osooo52 893 0 03 0 0 0 2 OF 05 DESCRIPTION OF WHAT OCCURRED:

A. Initial Conditions:

At, approximately 0614 MST on February 13, 1993, Palo Verde Unit 1 was in Mode 1 (POWER OPERATIONS) at approximately 100 percent power and normal operating temperature and pressure.

B. Reportable Event Description (Including Dates and Approximate Times of Major Occurrences):

Event Classificati'on: An event or condition that resulted in an automatic actuation of an Engineered Safety Feature (ESF)(JE).

At approximately 0614 MST on February 13, 1993, the normal supply breaker to the Unit 1, non-Class lE 13.8 kV, Intermediate Bus, NAN-S05, (SWGR)(EA) opened on overcurrent. This resulted in a Loss of Power (LOP) to the Unit 1 Train A Class lE 4.16 kV bus (BU)(EB). The LOP ESF signal automatically load shed the Class 1E 4.16 kV bus and started the Train A Emergency Diesel Generator (DG)(EX). The Emergency DG started and assumed the loads as designed. All equipment functioned as designed. No other ESF signals were actuated and none were required. Unit 1 continued to operate normally at 100 percent power throughout the event.

Technical Specification (TS) Limiting Condition for Operation (LCO) 3.8.1.1. ACTION a. was entered for one offsite circuit inoperable.

The non-Class lE, 13.8 kV power system receives off-si.te power from the 525 kV switchyard (SWGR)(FK). The non-Class 1E, 13.8 kV power system consists of one 525 to 13.8 kV startup transformer and six 13.8 kV switchgear per unit. The normal switching arrangement provides for each start-up transformer to supply power to two 13.8 kV Intermediate Buses (NAN-S05 and NAN-S06) of two different units. For example, Unit 1 transformer NAN-X03 supplies the normal power to bus NAN-S05 and transformer NAN-XOl supplies the alternate power to bus NAN-S05. The Intermediate Buses supply power to their respective 13.8 kV bus which in turn supplies the Class 1E 4.16 kV system through .an ESF transformer (XFMR)(EB).

An initial inspection of the switchgear by Operations personnel (utility, non-licensed), indicated that the normal supply breaker to the Unit 1 Intermediate Bus tripped on overcurrent., There was smoke in the metal outdoor switchgear enclosure, but no fire.

Troubleshooting by APS Maintenance and 'Engineering personnel (utility, non-licensed) determined that the normal supply breaker for switchyard control power (breaker NAN-S05F) had evidence of a

L'ICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITYNAME DOCKET NUMBER LER NUMBER PACE

,~: SEOUENTIAL 9." REVISION NUMBER <% NUMBER Palo Verde Unit 1 0 5 0 0 0 OF fault on the C phase, line side to bus interface. This caused the normal supply breaker for the Unit 1 Intermediate Bus to open on overcurrent as designed.

The damaged line side to bus interface for the normal switchyard control power breaker was removed. Switchyard control power was re-energized from its alternate supply breaker'. The Intermediate Bus normal supply breaker was racked out. After testing for grounds, the Intermediate Bus was. re-energized from its alternate supply. Preventive maintenance was performed on the Intermediate Bus normal supply breaker. No problems were found'nd the normal power supply breaker was returned to service. The Unit 1 Intermediate Bus was returned to a normal line-up. A Root Cause of Failure Analysis is being conducted on the damaged components removed from the switchyard control power switchgear'. TS LCO 3.8.1.1 ACTION a. was exited at approximately 1617 MST on February 13, 1993. Units 2 and 3 were not affected by this event.

C. Status of structures, systems, or components that were inoperable at the start of the event that contributed to the event:

Not applicable - no structures, systems, or components were inoperable at the start of the event which contributed to thi's event.

D. Cause of each component or system failure, if known:

The apparent cause of the failure was determined to be an overcurrent condition associated with the switchyard control power normal supply breaker C phase, line side to bus interface. APS Engineering personnel are conducting an Equipment Root Cause of Failure Analysis as discussed in Sections I.I and III'.

E. Failure known:

mode, mechanism, and effect of each failed component, if As described in Section I.B., the fault condition on the C phase of the normal supply breaker for switchyard control power caused the normal .supply breaker for the Unit 1 Intermediate Bus to open on overcurrent. This resulted in an LOP on the 13.8 kV Intermediate Bus and caused an LOP ESF signal to the Train A Class 1E 4.16 kV bus and an automatic start of the Train A Emergency DG.

F. For failures'f components, with multiple functions, list of systems or secondary functions that were also affected:

Not applicable - no failures of components with multiple functions were involved.

I LICENSEE EVENT REPORT (LER) TEXT CONTINUATION DOCKET NUMBER LER NUMBER PACE FACILITYNAME SEQUENTIAL e.~ REVISION YEAR gc N NUMBER SS NUMBER Palo Verde Unit 0 5 0 0.0 QFp 5 G. For a failure that rendered a train of a safety system inoperable, estimated time elapsed from the discovery of the failure until the train was returned to service:

Not, applicable - no failures'hat rendered a train of a safety system inoperable were involved.

H. Method of discovery of each component or system failure or procedural error:

The overcurrent condition was discovered during the inspection of the switchgear immediately following the event.

I. Cause of Event:

An investigation of this event is being conducted in accordance with the APS Incident Investigation Program. An initial inspection of the normal supply breaker to the Unit 1 Intermedi'ate Bus identified that the breaker had'pened on an overcurrent condition. An action plan for troubleshooting was developed and carried out.

The apparent cause of the overcurrent condition on the Intermediate Bus was a fault on the supply breaker for switchyard control power C phase, line side to bus interface (SALP Cause Code X: Other). There were no procedural or personnel errors which contributed to this event.

APS Engineering personnel are conducting an Equipment Root Cause of Failure Analysis of the damaged components to determine the cause and any additional corrective actions to prevent recurrence.

The results of this investigation will be included in a supplement to this report.

Safety System Response:

Following the LOP to the Train A Class 1E 4.16 kV bus, the Train A Emergency DG started and re-energized the associated ESF bus within the TS time requirement. The load sequencer initiated the required Load Shed signal and subsequently re-sequenced the following safety systems as required by design: Control Room Essential Ventilation (VI), Essential Cool'ing Water Pump (P)(BI),

Essential Spray Pond Pump (P)(BI) and Essential Chiller (CHU)(KM).

~5 r LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILTIYNAME DOCKET NUMBER LEA NUMBER PACE

',.'$ SEQUENTIAL ~P' REVISION yEAR NUMBER kr NUMBER Palo Verde Unit 5 28'3 .003 0 0 0 5 OF0 5 Failed Component Information:

An Equipment Root Cause of Failure Analysis, as discussed in Sections I.I and III.B, is being conducted. Failed component information will be identified in a supplement to this report.

II. ASSESSMENT OF THE SAFETY CONSEQUENCES AND IMPLICATIONS OF THIS EVENT:

The event, did not result in any challenges to the fission product barriers or result in any releases of radioactive materials. There were no safety consequences or implications as a result of the event. The event did not adversely affect the health or safety of the public.

III. CORRECTIVE ACTION:

A. Immediate:

The normal supply breaker for switchyard control power was removed from its cubical for troubleshooting and the damaged breaker to bus interface was removed. The normal supply. breaker for the Unit 1 Intermediate Bus was racked out for troubleshooting. Preventive maintenance was performed and no problems were identified.

B. Action to Prevent Recurrence:

As discussed in Section I.I and II.B., APS Engineering personnel are conducting an Equipment Root Cause of Failure Analysis to determine the failure mechanism of the damaged components. The results of this investigation will be included in a supplement to this report. This supplement is expected to be submitted by May 30, 1993.

IV. PREVIOUS SIMILAR EVENTS:

No previous similar events have been reported pursuant to 10CFR50.73, where a faulty supply breaker to the non-Class 1E 13.8 kV switchgear Intermediate Bus resulted in an LOP to a Class lE 4.16 kV bus and the initiation of an Emergency DG automatic starting signal.

V. 'DDITIONAL INFORMATION:

None

0