ML20094M014

Special Rept:On 951017,valid Failure of EDG Occurred While Performing Surveillance Test Procedure ST-6-092-316-1.Caused by Overvoltage Permissive Relay in Output Breaker Closing Logic Not Picking Up.Relay Recalibr & Returned to Svc

ML20094M014
Person / Time
Site:	Limerick
Issue date:	11/15/1995
From:	Boyce R PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9511210228
Download: ML20094M014 (2)

Text

.

• Ritert W. cayce

/, Plant Manager Limerick Generating Stawn w ~

~~

P'ECO ENERGY "="

• c-Limenck Generating Station PO Box 2300 Sanatoga, PA 19464-0920 215 3271200 Ext. 2000 T.S. 6.9.2 November 15, 1995 Docket No. 50-352 License No. NPF-39 2

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

SUBJECT:

Limerick Generating Station, Unit 1 Special Report for a Valid Emergency Diesel Generator Test Failure

REFERENCE:

Technical Specifications Sections 4.8.1.1.3 and 6.9.2 This Special Report is submitted pursuant to the requirements of Technical Specifications (TS) Section 6.9.2 as required by TS Surveillance Requirement 4.8.1.1.3. TS Surveillance Requirement 4.8.1.1.3 requires reporting of all diesel generator failures, valid or non-valid, within 30 days. The report is required to include the information recommended in Regulatory Position C.3.b of Regulatory Guide (RG) 1.108, " Periodic Testing of Diesel Generator Units as Onsite Electric Power Systems at Nuclear Power Plants,"

Revision 1, August 1977.

On October 17, 1995, with Unit 1 at 100% power, Operations personnel were performing Surveillance Test (ST) Procedure ST 092-316-1, "D12 Diesel Generator Fast Start Operability Test Run. "

During the performance of this ST procedure, the D12 Emergency Diesel Generator (EDG) Output Breaker f ailed to close from the Main Control Room hand switch. The D12 EDG was then declared inoperable at 0920 hours0.0106 days <br />0.256 hours <br />0.00152 weeks <br />3.5006e-4 months <br /> on October 17,1995.

Preliminary troubleshooting verified that the output breaker could only be closed locally from the test position. Further troubleshooting determined that an overvoltage permissive relay (i.e., 159 picking up/BG501-1)

. An evaluationin theofoutput breaker the relay closingthat determined logic waswere there not <

no visible signs of physical damage and that the relay was out of  !

calibration. Subsequently, the relay was recalibrated and returned -

to servige.r .

J i u .t 0f3 .  !

5 12 hh 2 [N ()

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Novembor 15, 1995

.Pags 2 of 2 Following the recalibration of the overvoltage permissive relay, a post-maintenance test (PMT) of the relay was performed. The PMT consisted of a D12 EDG run and subsequent loading of the EDG to verify relay setpoint and operation. The PMT was successfully completed and the D12 EDG was restored to an operable condition at 0006 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> on October 18, 1995. Calibration checks were made on the related relays on the D13 and D14 EDGs, and no problems were identified. The D11 EDG overvoltage permissive relay was verified by an engine run and closure of its output breaker. Subsequent testing of the Unit 2 EDGs indicated that there are no problems with the output breaker closure logic for these EDGs.  ;

A review was made to determine the cause for the out of calibration condition of the 159/BG501-1 overvoltage permissive relay. Initial information revealed that this relay is calibrated every 18 months during a D12 EDG overhaul. The most recent calibration check on this relay occurred in March 1995. The D12 EDG output breaker was successfully tested during the months following the March 1995 overhaul until this event. To further investigate this issue, the 159/BG501-1 relay will be replaced and sent to a company owned laboratory for analysis. A supplement to this Special Report will be issued if significant findings are identified from this analysis.

The D12 EDG failure was classified as a valid failure using the guidance of RG 1.108, Revision 1, August 1977, Section C.2.e(5).

Since this D12 EDG valid failure is the first failure in the last 20 valid demands, the _ ST - procedure monthly frequency is not  !

required to be changed in accordance with TS Section 4.8.1.1.2.a.

If you have any questions, please do not hesitate to contact Mr.

James L. Kantner at (610) 718-3400.

Very truly yours, i s DMS:cah cc: T. T. Martin, Administrator Region I, USNRC N. S. Perry, USNRC Senior Resident Inspector, LGS

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