05000318/LER-1981-006-03, /03L-0:on 810113 Diesel Generator 12 Switchgear Would Not Close in on 21 4-kV Bus Per Tech Spec.Caused by High Resistance at Secondary Disconnect.Continuity of Closing Circuit Interlocks Verified & Switchgear Tested

/03L-0:on 810113 Diesel Generator 12 Switchgear Would Not Close in on 21 4-kV Bus Per Tech Spec.Caused by High Resistance at Secondary Disconnect.Continuity of Closing Circuit Interlocks Verified & Switchgear Tested

ML20003B762
Person / Time
Site:	Calvert Cliffs
Issue date:	02/12/1981
From:	Lagiewski J, Rizzo P BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20003B755	List: 05000318/LER-1981-006, Forwards LER 81-006/03L-0 05000318/LER-1981-006-03, /03L-0:on 810113 Diesel Generator 12 Switchgear Would Not Close in on 21 4-kV Bus Per Tech Spec.Caused by High Resistance at Secondary Disconnect.Continuity of Closing Circuit Interlocks Verified & Switchgear Tested
References
LER-81-006-03L-01, LER-81-6-3L-1, NUDOCS 8102250456
Download: ML20003B762 (2)

LER-1981-006, /03L-0:on 810113 Diesel Generator 12 Switchgear Would Not Close in on 21 4-kV Bus Per Tech Spec.Caused by High Resistance at Secondary Disconnect.Continuity of Closing Circuit Interlocks Verified & Switchgear Tested

Event date:
Report date:
3181981006R03 - NRC Website

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NRC FORM 366 U. S. NUCLEAR REGULATORY COMMISSION mm LICENSEE EVENT REPORT i

CONTROL SLOCK: l l

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8 60 61 COCKET NUMSER 6tl 69 EVENT QATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROSABLE CONSEQUENCES h Io lal i At 1115, during the perfonnance of surveillance testing, #12 Diesel i

10:31 i Generator switchgear would not close in on #214KV bus per the reouire-1 10 41 I ments of T.S. 3.8.1.1.

The diesel was declared inoperable and the re-1 io is # l dundant oower sources verified. #12 Diesel Generator was tested and I

t o is 1 I returned to service at 1415. Thisis not a repetitive occurrence.

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9 10 11 12 13 18 19 20 sEOUENTIAL CCCURRENCE REPORT REVis80N LER<RO EVENT YEAR REPORT NO.

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36 37 40 41 42 43 44 47 CAUSE CESCRIPT10N AND CORRECTIVE ACTIONS h 11 loii Continuity of the closino circuit interlocks was verified. The switch-I li t i l I cear (G.E. Co. Tvoe AMH 4.76-250-ID) was cycled in test and normal co-1 i,i2i I sitions. Conclusion: a high resistance existed at a secondary discon-1 i i i 31 ;

nect which cleared uoon reinsertino the switchoear.

Disconnect contact l

Ii14 i I insoection is cart of existino PM orocedure.

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ACTtviTY CO TENT DELEAsED OF *ELEAsE AMOUNT OP ACTIVITY LOCAff0N OP RELEASE Ii Ie i LI]@ L7J@l NA l

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NAME OF PPEPARER J.S. Laqiewski/P.G. Rizzo (301) 269 4747/4786

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LER NO.

81 -0 6 DOCKET NO.

50-318 LICENSE NO. DPR-69 EVENT DATE 01-13-81 REPORT DATE 02-12-81 ATTACHMENT CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (CONT'D)

Immediate action was to verify all closing circuit interlock contacts were closed. This continuity check was made with the switchgear with-drawn from its housing. The switch in the Control Room was also veri-fied at this time. No high resistence or open contacts were discovered.

Maintenance personnel conducted a visual inspection of the unit includ-ing secondary disconnect contacts and noted no problems. They then cycled the switchgear successfully while it was withdrawn in the test position. After reinserting the unit to its normal position, it was cycled repeatedly from the Control Room with no further difficulty.

Because no mechanical or closing circuit problems were found and only the secondary disconnect contacts were not tested in an as-found con-dition, it is conceivable that a high resistence condition had existed at a secondary disconnect which prevented the closing coil from con-ducting sufficient current to operate the switchgear.

These disconnect contacts showed no mechanical damage nor signs of wear. They were found to be clean and smooth.

Inspection of the contacts is performed during preventive action on an annual basis. Since this is not a repetitive event given the large number of similar installations within the plant, no further preventive action is deemed necessar, at this time.