ML19260B076

LER 79-071/03L-0:on 791111,reactor Tripped Due to 500 Kv Breakers Opening & Causing Loss of 500 Kv Transmission Line 5052 & Unit 1 500 Kv Bus.Caused by Malfunctioning Solid State Relay Card in Breaker 552-43 Panel Replaced

ML19260B076
Person / Time
Site:	Calvert Cliffs
Issue date:	12/04/1979
From:	Heibel R BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19260B067	List: ML19260B066 ML19260B076
References
LER-79-071-03L, LER-79-71-3L, NUDOCS 7912060485
Download: ML19260B076 (2)

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[ o] d LAt 2000 on *:cyr ber lim 1979,_a faul t_in_the_500kv_circtti t t . breaker .552-43 ____j

[ o J i] [ caused that breaker to trip. 500kv breakers 552-22 and 552-G2 subsecuently _

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[ c,j :] l cpr.r.sd causi.)q a loss _of the 500kv trapsgission lir.e 5052_cildJgi t 1 500kv __ _ __ _ j

[fj}] [ Bus. The loss of the 500kv Bus caused a Reactor trin. At 0247 on I;ovember ]

[b]q j l',1979, af ter an_ inspection of breater 552 43. the electrical line-up was j

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42 43 L]@ lGl01810j@ 44 47 CAUEE D'5cR. MON AND CCRRECTIVE ACTIO'.S h FGT11 Investication of the static line relay panel for breaker 552-C revealed i Lilu l that a solid state relay card was malfunctioning and indicatino that 1

[i 2 lBhK 552-43 had failed to trip. This card was replaced and the breaker i 1 . I placed M ck in operation. I L'_L4_J l - ._

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LER ATTACll:tEilT LER fl0. 79-71/3L COCKET I;0. 50-317 EVENT DATE 11/11/79 REPORT DATE 12/04/79 ATTACH:1ENT CAUSE DESCRIPTION AtiD CORRECTIVE ACTION: (CONTINUED)

The relay test grcup was able to determine which protective relay had caused 552-43 to trip and subsequently trip the other 500kv breakers. However, once this relay card was removed from the relay panel for troubleshcoting it performed perfectly. Conditions could not be repeated in the field or in the lab to make the subject card duplicate t'ie output signal that had caused this event and that was present prior to that card's removal from the panel.

Despite the fa.ct that the fault could not ba repeated, the existing card was replaced with a new one, bhflh&Q 152l 017