AECM-89-0168, Special Rept 89-007/0:on 890804,diesel Generator 13 Failed to Properly Load During Monthly Functional Surveillance. Caused by Failure of Motor Operator Potentiometer in Governor Control Circuit.Potentiometer Replaced

Special Rept 89-007/0:on 890804,diesel Generator 13 Failed to Properly Load During Monthly Functional Surveillance. Caused by Failure of Motor Operator Potentiometer in Governor Control Circuit.Potentiometer Replaced

ML20246L927
Person / Time
Site:	Grand Gulf
Issue date:	08/31/1989
From:	Cottle W SYSTEM ENERGY RESOURCES, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
89-007-0, 89-7, AECM-89-0168, AECM-89-168, NUDOCS 8909070063
Download: ML20246L927 (2)

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BEEDugtEN, MC.

mi wm u .w-Vre Resent i Nriear Cuvotons August 31, 1985 j U;S." Nuclear. Regulatory Commission

. MailiStation F1-137

. - Washington,._D.C. 20555' Attention: : Document Control Desk Gentlemea:

SUBJECT:

Grand Gulf Nuclear Station 4 '

Unit 1 Docket No. 50-416 License No. NPF-29 Special Report 89-007/0 Emergency Diesel Generator.13

, Invalid Failure AECM-89/0168 On August 4, 1989 Diesel Generator 13 failed to properly load during performance 'of the monthly fenecional- surveillance. . The test was also .

intended to demonstrate operability of the' diesel generator following

~ maintenance. . Diesel Generator 13 was considered inoperable at the time of the test and the LCO actions required by Technical Specification 3.8.1.1.

. were being performed. .The offsite AC power sources and Diesel Generators 11

.:and 12 were operable.

When the diesel generator is synchronized to the bus for testing, the generator is~ initially loaded to approximately 350 KW. After this load is established and stabilized,'the' generator load is increased in 1000'KW increments with approximately 5 minute. hold' times between the increments. The diese1' generator successfully started and was successfully synchronized to the energized bus to approximately 350 KW. While increasing the load from 350 KW with the governor manual control handswitch, the engine fuel racks exhibited erratic motion accompanied by erratic load behavior. The diesel generator output dropped resulting in a trip on reverse power.

.An' investigation of the malfunction determined that the cause was a failure of the motor' operated potentiometer in the governor control circuit.

<  ; Incomplete-contact between the wiper arm and the variable resistor at a position equivalent to approximately 800 KW caused a control signal that

- decreased load.

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AECM-89/0168 Page 2 s.

The motor operated potentiometer was replaced and the diesel generator was retested satisfactorily. A maintenance history check revealed no j previous failures of this component.

SERI considers the test not to be a valid test or failure pursuant to Position C.2.e(2) of Regulatory Guide 1.108. The motor operated potentiometer is used to control load during synchronization to an energized bus. It is not used to control load during emergency operation. During emergency operation, the motor drives potentiometer would not be positioned to the defective spot and thus would not affect diesel generator operation. In addition, the reverse power trip is bypassed during emergency operation. The testing frequency remains at once per 31 days in accordance with the test schedule of Technical Specification Table 4.8.1.1.2-1.

This Special Report is submitted pursuant to Technical Specification 4.8.1.1.3.

Yours Truly,

/~Olr A ETC:cg cc: Mr. D. C. Hintz Mr. T. H. Cloninger Mr. R. B. McGehee Mr. N. S. Reynolds Mr. H. L. Thomas Mr. H. 0. Christensen Mr. Stewart D. Ebneter Regional Administrator U.S.-Nuclear Regulatory Commission Region II 101 Marietta St., N.W., Suite 2900 Atlanta, Georgia 30323 Mr. L. L. Kintner, Project Manager Office of Nuclear Reactor Pegulation U.S. Nuclear Regulatory Commission Mail Stop 14B20 Washington, D.C. 20555 l

l PCOM SPECIAL REPORT 89-007/0 - 2

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