ML20072U561

Special Rept 89-001-01:on 890201,output Breaker for DG 12 Failed to Close While Attempting to Parallel Generator W/ Energized Bus.Caused by Malfunction of Tachometer Transmitter.Upgraded Transmitters Installed

ML20072U561
Person / Time
Site:	Grand Gulf
Issue date:	04/12/1991
From:	Cottle W ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
89-001-01, 89-1-1, GNRO-91-00059, GNRO-91-59, NUDOCS 9104190203
Download: ML20072U561 (3)

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U'.S. Nuclear Regulatory Commission  !

-Mail Station P1-137 l Washington, D.C. 20555 -

Attention: Document Control Desk Gentlemen:

I SilBJECT: ' Grand Gulf Nuclear Station Unit 1 Docket No. 50-416 License.No NPF-29 ,

Special Report 89-001-01 Update to. Diesel Generator Failure to Load During Test

~GNR0-91/00059 On February 1,1989 at approximatelv 1020 during the performance of the

-monthly functional surveillance, the output breaker for Diesel Generator

.12 : failed to close while attemptii:9 to parallel the generator with an-energized bus. The diesel-generator was declared inoperable and a maintenance investigation was conducted. The=cause of the incident was-

determined to be a malfunction of a- tachometer transmitter. The transmitter was: replaced and the diesel generator functional test was isuccessfully completed by 2215 on February 1.

-The tachometer transmitter malfunction would not have prevented the diesel -

generatar-breaker from' closing in'the emergency operating' mode. The diesel generator is_ equipped with.two redundant._ start circuits. During_

non-emergency starts, the transmitter in each circuit.must function;to provide a' breaker closing permissive!when paralleling'the generator.to the  :>

grid.

During an emergency start, either tachometer transmitter can provide' the: breaker closing. permissive signal. Therefore, the unsuccessful-load attempt is not considered a valid test or failure in accordance-with position C.2.e(2)_of Regulator Gulde'1.108. The testing frequency of: Diesel Generator 12 remains at once per 31-days in accordance

--with the schedule of Technical Specification Table 4.8.1.1.2-1.

The failure of the transmitter (Airpax Model number 080-321-2112) was

.. attributed to an excessive voltage input to the transmitter during periods l of. battery equalization. Since February 1, 1989, GGNS has not experienced i any similiar failures.

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April 12, 1991 GNRO-91/00059 Page 2 of 3 Original plans were to install transmitters with a higher voltage input range to prevent recurrence of the failure. Following discussions with the supplier, it was determined that a qualified ' transmitter with a higher voltage input range was not available from any source.

GGNS was supplied with an upgraded version of the original transmitter.

The current rating of the internal relays for this type of transmitter was found to be below the actual current flow for our application. This deficiency was documented on a Material Nonconformance Report.

!- GGNS installed the upgraded transmitters and made wiring changes to l resolve the current rating deficiency with a Minor Change Package during RF04 on the Divisio.i 1 Diesel Generator. The wiring changes reduce the current load on the internal relays to improve reliability.

GGNS currently plans to install the upgraded transmitters and make wiring l changes to the Division 2 Diesel Generator during RF05, in accordance with I the Minor Change Package.

Yours truly, wrem WTC/cg cc: Mr. D. C. Hintz l Mr. R. B. McGehee l Mr. N. S. Reynolds-

! Mr. H. L. Thomas Mr. J. L. Mathis Mr. Stewart D. Ebneter l Regional Administrator

').S. Nuclear Regulatory Commission l Region II 101 Marietta St., N.W., Suite 2900 Atlanta, Georgia 30323 l

L Mr. L. L. Kintner, Project Manager Office of Nuclear Reactor Regulation L V.S. Nuclear Regulatory Commission Mail Stop 11021 Washington, D.C. 20555 l

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April 12, 1991 GNRO-91/00059 Page 3 of 3 1

bec: Mr. C. W. Angle l Mr. M. A. Dietrich 1 Mr. C. R. Hutchinson Ms. F. K. Mangan Mr. M. J. Meisner Mr. G. W. Muench Mr. T. E. Reaves MR. R. Ruffin Mr. F. W. Titus Mr. G. A. Zinke SRC Secretary File (LCTS) (2)

File (RPTS)

File (NL)

File (Central) (3) i SR890101/SCHPFLR - 3