05000529/LER-1989-001, :on 890103,total Loss of Offsite Power to Class 1E 4.16 Kv Busses 2E-PBA-S03 & 2E-PBB-S04 Occurred.Caused by Reduced Impulse Withstand Voltage Rating Due to Rain.Failed Bushings on Each Transformer Replaced

:on 890103,total Loss of Offsite Power to Class 1E 4.16 Kv Busses 2E-PBA-S03 & 2E-PBB-S04 Occurred.Caused by Reduced Impulse Withstand Voltage Rating Due to Rain.Failed Bushings on Each Transformer Replaced

ML17304B366
Person / Time
Site:	Palo Verde
Issue date:	07/27/1989
From:	Haynes J, Shriver T ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
192-00503-JGH-T, 192-503-JGH-T, LER-89-001, LER-89-1, NUDOCS 8908040189
Download: ML17304B366 (16)

LER-1989-001, on 890103,total Loss of Offsite Power to Class 1E 4.16 Kv Busses 2E-PBA-S03 & 2E-PBB-S04 Occurred.Caused by Reduced Impulse Withstand Voltage Rating Due to Rain.Failed Bushings on Each Transformer Replaced

Event date:
Report date:
5291989001R00 - NRC Website

text

gC CEIZRATED D1 BUTION DEMONSTRATIO.'i SYSTEM S

~

REGULATORY INFORMATION DISTRXBUTION SYSTEM (RIDS)

ACCESSION NBR-8908040189 DOC.DATE: 89/07/27 NOTARIZED: NO DOCKET FACIL:STN-50-529 Palo Verde Nuclear Station, Unit 2, Arizona Publi 05000529 AUTH.NAME AUTHOR AFFILIATION SHRXVER,T.D.

Arizona Public Service Co. (formerly Arizona Nuclear Power HAYNES,J.G.

Arizona Public Service Co. (formerly Arizona Nuclear Power RECXP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 89-001-01:on 890103,ESF actuation caused by loss of power to Class 1E 4.6 kv busses.

W/8 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED: LTR 3 ENCLL SIZE:

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

NOTES:Standardized plant.

05000529 RECIPIENT ID CODE/NAME PD5 LA CHAN,T INTERNAL: ACRS MICHELSON ACRS WYLIE AEOD/DSP/TPAB DEDRO NRR/DEST/ADE 8H NRR/DEST/CEB 8H NRR/DEST/ICSB 7

NRR/DEST/MTB 9H NRR/DEST/RSB 8E NRR/DLPQ/HFB 10 NRR/DOEA/EAB 11 NUDOCS-ABSTRACT RES/DSIR/EIB RGN5 FILE 01 EXTERNAL EGGG WILLIAMSE S L ST LOBBY WARD NRC PDR NSIC MURPHY,G.A NOTES COPIES LTTR ENCL 1

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Arizona Public Service Company PALO VERDE NUCLEAR GENERATING STATION P 0 BOX 52034

~

PHOENIX, ARIZONA85072-2034 192-00503-JGH/TDS/JEM July 27, 1989 U.

S. Nuclear Regulatory Commission NRC Document Control Desk Washington, D.C.

20555

Dear Sirs:

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Unit 2 Docket No.

STN 50-529 (License NPF-51)

Licensee Event.Report 89-001-01 File:

89-020-404 Attached please find Supplement Number 1 to Licensee Event Report (LER) No.

~ 89-001-00 prepared and submitted pursuant to the requirements of 10CFR 50.73.

In accordance with 10CFR 50.73(d),

we are herewith forwarding a copy of this report to the Regional Administrator of,the Region V Office.

If you have any questions, please contact T. D..Shriver, Compliance Manager at (602) 393-2521.

Very truly yours,

//

. i/ii/i"~v' J.

G.

Haynes Vice President'uclear Production JGH/TDS/JEM/kj Attachment cc:

W.

F.

Conway D.

B. Karner E.

E.

Van Brunt, Jr.

J.

B. Martin T. J. Polich M. J.

Davis A. C.

Gehr INPO Records Center (all w/a)

f

NRC Form 345'94L)

I LICENSEE EVENT REPORT ILER)

US. NUCLEAR REOULATOAYCOMMISSION APPROVEO OMS NO. 3(500104 EXPIAESI SI31ISS FACILITYNAME l1)

DOCKET NUMSEA l2)

PA Pal o Verde Unit 2 TITLE (4) 05000529>oF06 ESF Actuation Caused by Loss of Power to Class lE 4. 16 kv Busses EVENT DATE (SI LER NUMSER IS)

REPORT DATE (7l O'THER FACILITIESINVOLVED(SI MONTH OAY 010 3

YEAR 8

9 YEAR 8

9 SEDUENTIAL pose NVMSEII 0 01 MONTH OAY YEAR NVMSER 010 72 78 9

N/A N/A FACILITYNAMES DOCKET NUMSERIS) 0 5

0 0

0 0

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OPERATINO MODE (~I 1

POWE R LEYEL 1

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THIS AEPOR'7 IS SUSMITTED PURSUANT TO THE REDUIREMENTS OF 10 CFR gr IChnh one or more or the IPIIo~'npi (11) 73.71(bl 73.71(cl OTHER (Specify In Apttrett INipvrend In Test, HIICForm dddAI NAME Timothy D. Shriver, Compliance Manager TELEPHONE NVMSER AREA CODE 60 239 3-2521, COMPLE'TE ONE LINE FOR EACH COMPONENT FAILURE OESCAISEO IN THIS REPORT (13)

CAUSE

SYSTEM E A COMPONENT X F,MR MANUFAC TUREA W1 20 Y

jYjgj%ai%4$

COMPONENT MANUFAC.

TURER EPOATASLE TO NPRDS i(s((rgb)@iAG@oY~

SUPPLEMENTAL AEPOAT EXPECTED (14)

MONTH DAY YEAR YES IIIyn, comprere fXPfCyfDSVSMISSIDH DAyfl X

No EXPECTED SVSMISSION DATE (15)

ASSTRACT ILimrt to 1400 rpetn. Ie., epprorimenly Mreen IInpre reeve rypelvrrtren irnnI (14)

At 1940 MST on January 3,

1989, Palo Verde Unit 2 was in Mode 1

(POWER OPERATION) at approximately 100 percent power when a total loss of offsite power to the class lE 4. 16 kv busses 2E-PBA-S03 and 2E-PBB-S04 occurred.

The loss of power (LOP) to busses 2E-PBA-S03 and 2E-PBB-S04 generated an Engineered Safety Features (ESF) signal which automatically started both "A" and HBR Diesel Generators.

The diesel generators started satisfactorily and assumed the loads on the 4. 16 kv class 1E busses.

At approximately 1959 MST on January 3,

1989 a Notification of. Unusual Event (NUE) was declared due to the loss of both offsite power sources to the in-plant class lE busses.

The NUE was terminated at approximately 1648 MST on January 4,

1989 after offsite power was restored to one of the class lE 4. 16 kv busses.

The loss of power (LOP) was caused by a reduced impulse withstand voltage rating due to rain saturation of contamination on the ESF transformer

bushings, and a possible ground potential rise attributed to lightning in the area.

This allowed a fault to initialize at the ESF transformer bushings.

The contamination is a build up of mineral deposits from misting of the cooling towers.

Two bushings on each transformer failed due to the fault and were replaced.

NAC Corm 344

4l

NRC Fe/es 344A 1943 I LICENSEE EVENT REPORT ILER) TEXT CONTINUATION U.S. NUCLEAR REOULATORY COMIAISSION APPROVEO OMS NO 3150W104 EXPIRE9: 5/31/SS FACILITYNAME III OOCRET NUMSER (31 LER NUMSER ISI 5t Q V5 NTIAL NVMetm mtV/5/ON NVM441 PACE ISI Palo Verde Unit 2 TEXT ////sso/4 emcee ie tete/eme(

s/ee ~N/IC/ro/ms 3$5A3/ (17)

DESCRIPTION

OF WHAT OCCURRED:

A.

Initial Conditions:

o so oo5 2989 00 l 01.02 oFO 6

B.

At 1940 HST on January 3,

1989, Palo Verde Unit 2 was in Hode 1

(POWER OPERATION) at approximately 100 percent power.

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

Event Classification:

An event or condition that resulted in an automatic actuation of an Engineered Safety Feature (ESF)(JE).

At approximately 1940 HST on January 3,

1989, Palo Verde Unit 2 was in Hode 1

(POWER OPERATION) when a complete loss of offsite power to the 4. 16 kv class 1E busses (BU)(EB) 2E-PBA-S03 and 2E-PBB-S04 occurred.

The loss of power (LOP) was caused by a reduced impulse withstand voltage rating due to rain saturation of contamination on the ESF transformer

bushings, and a possible ground potential rise attributed to lightning in the area.

This allowed a fault to initialize at the ESF transformer bushings.

The contamination is a

build up of mineral deposits from misting of the cooling towers.

ESF Service Transformer Normal Supply Breakers (BKR)(EA) 2E-NAN-S03A and 2E-NAN-S04A tripped on Instantaneous Overcurrent and Phase Differential which caused a

LOP to the class 1E busses 2E-PBA-S03 and 2E-PBB-S04.

Due to the LOP on class 1E busses 2E-PBA-S03 and 2E-PBB-S04 an ESF LOP signal was generated which load shed the busses and automatically started the RA" and RBR Emergency Diesel Generators (DG)(EK).

The DG's started and assumed the loads on 2f-PBA-S03 and 2E-PBB-S04 as designed.

Technical Specification (T.S.) Limiting Condition for Operation (LCO) 3.8. 1. 1 ACTIONs "aR and "dU were entered at 1940 HST on January 3,

1989.

The loss of both offsite power sources to the in-plant class 1E busses led to the declaration of a Notification of Unusual Event (NUE) at approximately 1959 HST on January 3,

1989 in accordance with approved Emergency Plan Implementing Procedures.

At approximately 2010 HST on January 3,

1989 the appropriate state and local agencies were notified via the Notification and Alert Network (NAN).

The Nuclear Regulatory Commission (NRC) Operations Center was notified at approximately 2034 HST on January 3,

1989 via the Emergency Notification System (ENS).

The NUE was reported in Special Report 2-89-001 on January 9,

1989.

Following the LOP load shed the Control Room Operators (utility, licensed) identified that the supply breaker for non-class 1E 480

'smg

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/9 43 ~

L

NRC Perrrr SSSA'445 I

LICENSEE EVENT REPORT (LERI TEXT CONTINUATION U.S. NUCLEAR REOULATORY COMMISSION APPROVEO OMS NO. 5150WIO(

EXPIRES: 8/ll/88 PACILI'TYNAME (11 OOCKET NUMSER tll LER NUMSER (Sl PACE (SI Palo.Verde Unit 2 TEXT /// rrrrrre ance ir t54r/15/E rrPP aANiaWNRC-foerr 8/E/ASI ((TI o

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5 2 9

YEAR;~

8 9

SEQVENTIAL NVM ER 0 0 1

AEVl5KIN MVMPEA

01. 03 OF 0 6

volt Motor Control Center (HCC)(EC)(NHN-H72) was open due to a lockout relay (86)(EA) trip.

Protective Relaying and Control (PR&C) personnel (uti,lity, non-licensed) inspected the breaker and found no tripped flags and no indication of a problem in the breaker.

The Shift Supervisor (utility, licensed) directed the operator to reset the 86 lockout and close the breaker.

The breaker closed as designed, and no additional problems were experienced with the breaker.

Troubleshooting and rework of the ESF transformers was conducted in accordance with approved work control documents.

It was identified that two bushings on each. transformer were damaged and the bushings were replaced.

The ESF transformers were not damaged.

After satisfactory completion of appropriate retests, ESF transformer 2E-NBN-X04 was energized from offsite power at approximately 1438 HST on January 4,

1989.

At approximately 1646 HST on January 4,

1989, transformer 2E-NBN-X04 was paralleled with RB" diesel generator and offsite power was restored to class IE bus 2E-PBB-S04.

At approximately 1648 HST on January 4,

1989 the NUE was terminated due,to offsite power being restored to one class IE 4. 16 kv bus.

LCO 3.8. 1. 1 ACTION RdR was then exited.

At approximately 1808 HST on January 4,

1989, transformer 2E-NBN-X03 was energized from offsite power.

At approximately 1925 HST on January 4,

1989, transformer 2E-NBN-X03 was paralleled with RA" diesel generator and offsite power was restored to class 1E bus 2E-PBA-S03.

LCO 3.8. 1. 1 ACTION RaR was then exited.

C.

The response of the Operations staff to the LOP and their subsequent recovery actions were both appropriate and timely.

There were no operator errors that contributed to the event.

Status of structures,

systems, or components that were inoperable at the start of the event that contributed to the event:

D.

Not applicable

- no structures,

systems, or components were inoperable at the start of the event that contributed to the event.

Cause of each component or system failure, if known:

r The cause of the failure of the bushings was due to a reduced impulse withstand voltage rating due to rain saturation of contamination of the ESF transformer

bushings, and a possible ground potential rise attributed to lightning in the area.

This allowed a fault to initialize at the ESF transformer bushings.

The contamination is a build up of mineral deposits from misting of the cooling towers.

'rAC / 0AM 554A IS Slr

I!

NRC FPNII 388A (843 I LICENSEE EVENT REPORT ILER) TEXT CONTINUATION U.S. NUCLEAR REOULATORY COMMISSION APPROVED OM8 NO 3ISOWI04 EXPIRES.'/31/88 FACILITYNAME (II OOCXET NUMSER (3l LER NUMSER (SI PACE (SI Palo Verde Unit. 2 TEXTO'IN44 44444 (4 /4444448 444 ~ //48Ar/K/ICAr/II3(E(A'4/ (17l o

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E.

Failure mode, mechanism, and effect of each failed component, if known:

The failed bushings created a line to ground fault and caused the transformer supply breakers to trip open creating the LOP to the class lE 4.16 kv busses.

G.

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

Not applicable

- the failed bushings do not have multiple functions.

For 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 safety system trains were rendered inoperable due to this event.

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

The failed bushings were identified during troubleshooting/rework of the ESF transformers.

I.

Cause of Event

The cause of the event, has been determined to be a reduced impulse withstand voltage rating due to rain saturation of contamination on the ESF transformer bushings, and a possible ground potential rise attributed to lightning in the area.

This allowed a fault to initialize at the ESF transformer bushings.

The contamination is a

build up of mineral deposits from misting of the cooling towers.

J.

Safety System

Response

The following safety systems actuated in response to the LOP.

These responses are in. accordance with system design.

Diesel Generators A and B

Control Room Essential Ventilation A and B

All essential battery chargers and voltage regulators re-energized.

4.

Auxiliary Feedwater Pump B

5.

Essential Cooling Water Pumps A and B

6.

Essential Spray Pond Pumps A and B

7.

Essential Chillers A and B

8.

Battery Room Essential Exhaust Fans A and B

9.

Condensate Transfer Pumps A and B

10. Diesel Generator Essential Ventilation Units A and B

4AC II/AM)44A l9 43 I

0

NRC Form 39SA (9431 LICENSEE EVENT REPORT ILER) TEXT CONTINUATION U.S. NUCLEAR REGULATORY COMMISSION APPROI/EO OMS NO, 3(50&104 EXPIRES: 8/31/88 FACILITYNAME (11 DOCKET NUMSER LTI LER NUMSER (8(

xiii SEGI/ENTIAL NUMSSR

>w IISVISION

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Palo Verde Unit 2 TEXT /// more soooe is IssFsowE oso aANiona/ HRC %%derr 3/F(A'/ (17) o so o o 52 98 9

0 0 1

01, 05oF 0

6 K.

Failed Component Information:

The failed bushings are manufactured by Westinghouse.

and are style

¹234C115G05.

II.

ASSESSMENT OF THE SAFETY CONSEQUENCES AND IMPLICATIONS OF THIS EVENT:

Throughout the event, the plant remained stable at approximately 100 percent power.

Diesel Generators A and B started and assumed all safety related loads as required.

The event did not result in any challenges to fission product barriers or result in any releases of radioacti.ve materials.

Therefore, there was no threat to the health and safety of the public.

III.

CORRECTIVE ACTIONS

A-.

Immediate:

B.

Two failed bushings on each transformer were replaced.

The transformers were inspected/tested and found not to be damaged before re-energizing them.

Action to Prevent Recurrence:

Several

corrective actions

have been or will be implemented, in all three (3)

PVNGS units, to prevent recurrence.

They include:

Installation of a drip loop on each conductor leading to the 15 kv bushings of each ESF transformer has been completed in all three PVNGS units.

The bushings on each ESF transformer in all three PVNGS units were cleaned.

Creepage extenders have been installed on the ESF transformer high side bushings in Unit 2.

In Units 1

and 3 creepage extenders have been installed on one ESF transformer and will be installed on the other ESF transformers during the present outages.

A program will be implemented for routine washing of all

bushings, insulators and other porcelain devices subject to cooling tower drift.

This program is expected to be implemented by August 31, 1989.

IV.

PREVIOUS SIMILAR EVENTS

There have not been any previous similar events reported.

Other events reporting a

LOP to class

4. 16 kv busses involved various causes (i.e.,

rrlc Ir/r\\M sooA l9 93>

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NRC PoIIS 888A

/843 I LICENSEE EVENT REPORT (LER) TEXT CONTINUATION U.S. NUCLEAR REOULATORY COMMISSION APPROVEO OMS NO 3150WI04 EXPIRESI 8/SI/88 PACILI'TYNAME III OOCKET NVMSER ISI

'YEAR LER NUMSER (8) 58OUENTIAL NUM Ell II8VIS IQN NUMOSII PACE ISI Palo Verde Unit 2 TEXt ///mP/8 saece /8 /Pou/PNE IMP mAISSPN////IC'hem DRESS/ IITI o

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personnel

error, equipment malfunction).

No previous LOP event was caused by a reduced impulse withstand voltage rating due to rain saturation of contamination on the ESF transformer bushings.

Therefore, no previous actions

.to prevent recurrence could have prevented this event.

NIIC I OEM N4A I98)<

11.