05000237/LER-1985-001, :on 850104,4-kV Breaker 2329 Failed to Trip Open During Relay Testing.Caused by Four Disconnected Wires in Trip Logic.Wires Reconnected

:on 850104,4-kV Breaker 2329 Failed to Trip Open During Relay Testing.Caused by Four Disconnected Wires in Trip Logic.Wires Reconnected

ML20099G264
Person / Time
Site:	Dresden
Issue date:	02/21/1985
From:	Rolonda Jackson, Scott D COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF ADMINISTRATION (ADM)
References
85-210, LER-85-001, LER-85-1, NUDOCS 8503140510
Download: ML20099G264 (4)

LER-1985-001, on 850104,4-kV Breaker 2329 Failed to Trip Open During Relay Testing.Caused by Four Disconnected Wires in Trip Logic.Wires Reconnected

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(ii)
2371985001R00 - NRC Website

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Supplemental Report:

Date of previous report 1/30/85 PACILITV NAME 11)

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During unit refueling outage, tle 4 KV breaker 2329 (Bus 23-1 main feed breaker) failed to trip open while the Operational Analysis Department (OAD) was conducting breaker differential relay testing. Safety significance was minimal since there was redundant tripping logic that would have operated the breakers in an identical manner for a differential fault and the unit was In a refueling outage.

The cause of the breaker failure was disconnected wires in the tripping logic.

In reviewing the breaker's work history since the last successful test (3/8/83), it was found that no work was performed during this period. Thus, j

the reason for the disconnected wires is unknown. A work request was written to correct the problem and the wires were subsequently reconnected. After successful testing, the breaker was returned to service.

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During unit refueling outage, the 4 KV breaker 2329 (Bus 23-1 main feed breaker) failed to trip open while the Operational Analysis Department (OAD) was conducting breaker dif ferential relay testing.

The OAD Test Engineer inspected the breaker's trip logic and found four (4) disconnected wires.

Thesewireswereconnectedtobreaker2302\\lockoutrelaycontactinthe tripping logic of breaker 2329. A survey of differential current relays on bus 24-1, 34-1and33-1wasmadeandallvjreintact.

In addition, OAD has tested other similar breakers and found no Iroblems. They plan to test the remaining seven 4 KV breakers prior to unit startup. The Unit Three 4 KV breakers were tested since the last cycle an no problems of this type were identified.

Therefore, as a result of the s rvey, and since the wires were disconnected in a manner indicative of norma removal, Dresden believes that-this incident was not one of malicious intent. but was simply a personnel error.

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The OAD staff indicated that the breaker had peen successfully tested when the identical surveillance was performed durihg the previous refueling outage (3/8/83).

A review of the breaker's work his;ory revealed no work conducted since that time.

Thus, the reason for the di$ connected wires is unknown.

The wires were reconnected and the breaker tripped successfully when tested.

Despite the disconnected wires in the tripping logic of breaker 2329, the breaker would have still tripped on a differentgial fault.

This would have occurred from the energizing of the lock-out relay which trips breaker 2302, consequently tripping breaker 2329 through the ~B auxiliary contact of breaker 2302.

Because of this redundancy, the safety significance was minimal. First occurrence of this type at Dresden.

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SUPPLEMENTAL REPORT TO DIR/LER DVR N0.

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PART 1 TITLE OF EVENT OCCURRED 1/4/85 1700 Bus 23-1 to Bus 23 Breaker Protective Relaying DATE TIME REASON FOR SUPPLEMENTAL REPORT This sunnlemental renort is beine submitted because of the request by the resident NRC Inspector.

PART 2 ACCEPTANCE BY STATION REVIEW D

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0 Telephone 815/942-2920 Commonwealth Edison Dresden Nucle:r Power St ti:n R.R. #1 Morris, Illinois 60450 February 25, 1985 DJS Ltr #85-210 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Supplement to Licensee Event Report #85-001-1, Docket #050237 is beitig submitted as required by Technical Specification 6.6, NUREG 1022 and 10 CFR 50.73 (a)(2)(ii). This supplement is being submitted to supply

additional information

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Scott Station Superintendent Dresden Nuclear Power Station DJS/kjl Enclosure cc J.G. Keppler, Regional Administrator, Region III File /NRC File / Numerical l

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