ML19290C256

LER 79-126/03L-0:on 791209,diesel Generator DG 1-1 Experienced Load Swings & Electrician Racked Out Wrong Breaker Making DG 1-2 Inoperable.Possibly Caused by Electronic Governor or Voltage Regulator Problems

ML19290C256
Person / Time
Site:	Davis Besse
Issue date:	01/05/1980
From:	Hartigan J TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19290C255	List: ML19290C254 ML19290C256
References
FOIA-81-159 LER-79-126-03L, LER-79-126-3L, NUDOCS 8001100430
Download: ML19290C256 (3)

Text

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? 60 61 DOCKE T NUY3 ER EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES h I o l 21 l On December 9,1979, during the performance of Diesel Generator (DG) Monthly Test, 1000 101 and again when o 3 l DG l-1 experienced lo;td swings as the load was increased about lo a the load was increased to 2500 101. During maintenance investigation, an electrician l s I mistakenly racked out the wrong breaker which made DG 1-2 inoperable. For 20 minutes l o

1016 l l the station was in violation of Technical Specification 3.8.1.2 (without a DG) . l 0 7 l There was no danger to the health and safety of the public or station personnel. Off-l a i site power was available to safety systems in the plant. (NP-33-79-146) l o

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44 47 34 33 36 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS i o l The cause of the load swings may possibly be from an electronic governor or voltage i i l regulator problems. Under Maintenance Work Order 79-3230, the load swing war inves-1 j

i 2 1 ticated. ST 5081.01 was successfully run later in the day, and DG l-1 was declared Safety tagging liI3l l operable. Power Systems will investinate the governor problem.

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DVR 79-187,194AME OF PREPARER

TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-79-146 DATE OF EVENT: December 9, 1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Swinging load on Diesel Generator 1-1 and rackaut of wrong Diesel Generator output breaker Conditions Prior to Occurrence: The unit was in Mode 5, with Power (MWT) = 0, and Load (Gross MWE) = 0.

Description of Occurrence: While performing ST 5081.01, Diesel Generator (DG) Monthly Surveillance Test on DG l-1 the load started swinging frou 1000 KW to 3000 KW as load was raised above 1000 KW. The operator stopped raising the load to inspect the voltage regulator, and the load swinging ceased. The load was then raised to 2500 KW. A few minutes later, the load started swinging from 1800 KW to 3 00 KW at which time DG l-1 was shutdown. About an hour later DG l-1 was restarted so maintenance could check out the electronic governor. The unit was running at 2500 KW for about 35 minutes and then started to swing from 800 KW to 3000 KW. The unit was unloaded and removed from service.

At this time, the Shift Foreman instructed a plant electrician to rack out AC101, DG l-1 output breaker. The electrician mistakenly racked out AD101, DG l-2 output breaker.

Approximately 15 minutes later, it was noticed that AD101 was racked out instead of AC101. AD101 was promptly racked in and AC101 was racked out. For approximately 20 minutes, the station was in the action statement of Technical Specification 3.8.1.2 which requires one DG to be operable in Modes 5 or 6.

Designation of Apparent Cause of Occurrence: At this time, it is unknown as to why DG 1-1 was experiencing load swings. The occurrence may possibly have been caused from an electronic governor or voltage regulatory problem, or from the fact that the bus voltage was high.

The occurrence of the electrician racking out the wrong breaker has been designated as personnel error.

Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel. Offsite power was available to safety systems in the plant.

Corrective Action: A small amount of oil was added to the governor and ST 5081.01 was run later on in the day of December 9, 1979 and was completed successfully. DG l-1 was then declared operable. Maintenance Work Order (MNO) 79-3230 was issued to troubleshoot the load swinging problem. Power Systems is scheduled in to thoroughly investigate the voltage regulator and governor.

LER #79-126 b

S TOLEDO EDISON COMPANY DAVIS-BESSE NUC' EAR P0h'ER STATION UNIT ONE PAGE 2 SUPPLEMENTAL INFORMATION FOR LER NP-33-79-146 Maintenance training on AD 1803.00, Safety Tagging, will be established.

Failure Data: A similar problem was found on DG l-1 as detailed on Licensee Event Report NP-33-78-58.

LER #79-126 1727 227