ML18093A384

Special Rept 87-3:on 870820,nonvalid Test Failure Involving Diesel Generator 2B Occurred.Cause Not Determined.Field Brushes & Slip Ring Assembly Inspected & Cleaned to Eliminate Possible Grounding Paths Due to Carbon Particles

ML18093A384
Person / Time
Site:	Salem
Issue date:	09/16/1987
From:	Zupko J Public Service Enterprise Group
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
87-3, NUDOCS 8709280313
Download: ML18093A384 (3)

Text

Public Service Electric and Gas Company P.O. Box E Hancocks Bridge, New Jersey 08038 Salem Generating Station September 16, 1987 U. S. Nuclear/Regulatory Commission Document Control Desk Washington, DC 20555

Dear Sir:

SALEM GENERATING STATION LICENSE NO. DPR-75 DOCKET NO. 50-311 UNIT NO. 2 ii

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SPECIAL REPORT 87-3 I

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-B This Special Report addresses a non-valid test failure of ID. 2B Diesel Generator occurring on August 20, 1987. This report is being submitted pursuant to the requirements of Technical Specification Surveillance 4.8.1.1.4.

Sincerely yours, J.V:.&:Je*

General Manager-Salem Operations MJP:pc Distribution 8709280313 8750090016311

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The Energy People 95-2189 111 M) 12-84

SPECIAL REPORT NUMBER 87tt PLANT IDENTIFICATION:

Salem Generating Station - Unit 2 Public Service Electric & Gas Company Hancock's Bridge, New Jersey 08038 IDENTIFICATION OF OCCURRENCE:

2B Diesel Generator - Non-valid Failure Event Date{s): 8/20/87 Report Date: 9/16/87 This report was initiated by Incident Report No.87-317 CONDITIONS PRIOR TO OCCURRENCE:

• Mode 6 - Reactor Power 0% - Unit Load O MWe DESCRIPTION OF OCCURRENCE:

This special report describes a non-valid test failure involving 2B Diesel Generator occurring on August 20, 1987. This report is submitted for informational purposes in accordance with Technical Specification Surveillance Requirement 4.8.1.1.4 and contains the information required by Regulatory Guide 1.108, Revision 1, August 1977, Regulatory Position C.3.b.

Surveillance Requirement 4.8.1.1.4 states:

"All diesel generator failures, valid or non-valid, shall be reported to the Commission pursuant to Specification 6.9.1 *** "

On August 20, 1987, the No. 2B Diesel Generator required surveillance test (Surveillance Procedure SP(O) 4.8.1.1.2., "Electrical Power Systems - Emergency Diesels") was manually terminated upon actuation of the Field Ground Alarm coupled with a flag of the overcurrent relay. The D/G was taken out of service pending results of investigations.

APPARENT CAUSE OF OCCURRENCE:

The root cause of the D/G Field Ground Alarm has not been determined to date. The alarm is intermittent, of short duration and self-correcting. It does not last long enough for troubleshooting methods to be effective.

ANALYSIS OF OCCURRENCE:

A single ground to field does not pose an immediate operability problem, however, should another ground of opposite polarity develop at the same time the intermittent ground occurs then equipment damage could result.

The instantaneous overcurrent relay flag indicates either the relay had been jarred, an overcurrent condition existed for a short period

SPECIAL REPORT 87-3 -.2-

~ ANALYSIS OF OCCURRENCE: (cont'd)

- of time, or a current spike had passed through the relay's sensing coil. The presence of this flag was unrelated to the field ground indication and is not an unexpected phenomenon during breaker operation. An actual overcurrent would have tripped the diesel output breaker and dropped the overcurrent flag at the relay.

The termination of the D/G test prior to its completion constitutes a non-valid test failure as described in Regulatory Guide 1.108.

In Mode 6, only two (.2) D/G's are required to be operable as per Techn~cal Specification 3.8.1.2. Nos. 2A and 2C D/G's remained operable when No. 2B D/G was taken out of service. Therefore, this event did not impact the health and safety of the general public.

CORRECTIVE ACTION:

The D/G manufacturer was contacted to discuss the circumstances surrounding this non-valid test failure. As a result of the discussions, the following will be done to No. 2B D/G during the next diesel outage of sufficient duration:

1. Inspection and cleaning of the generator field brushes and slip ring assembly to eliminate possible grounding paths due to carbon particles;

2. Megger the generator field windings;

3. Megger the saturable transformer which is used to control the field current; and

4. Engineering evaluation of the investigation results to determine if disassembly of the generator and inspection of the field winding (rotor) is required.

Gen<J:t:+/-e.

Salem Operations MJP:pc SORC Mtg.87-071