ML19270G653

RO 79-057/01T-0 on 790424:potential Overload exists;4,160 Volt Transfer Bus & Feeder Breakers Are Not Capable of Continually Carrying Full Load Current.Caused by Improper Sizing of Transfer Bus Equipment

ML19270G653
Person / Time
Site:	North Anna
Issue date:	04/25/1979
From:	VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
References
NUDOCS 7906140475
Download: ML19270G653 (1)

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Virginia Electrie and Power Cowarv NPF-4 North Anna Pc-er Station. Unit 1 79 AFR25 A 8., 32 Decket No. 50- E8 24 Hcur Reportable Event Written Folicw-Up Event: Transfer Bus Overloads LER/R0 79-057/01T-0 Cn 4/24/79, tra Station Personcel at North Anna Pcuer Station were informed of a potential for an overicad condition en the Station Transfer Bus. As a result of a review of the electrical require:wnts during cc.rbine unit aperation of Units 1 and 2. the 4160 volt transfer bus and transfer tus feeder breakers are not capable of continually carrying full load current for certain canditions. For example, if Unit 1 was cperating and Unit 2 was in the prccess of startira up, the additional load on the transfer bus if Unit I were to trip would result in an overload of the above mentioned ccepo-nents. 'This overicad would not result in an 1:arediate trip, but wculd result in heating up the transfer bus ctmponents.

This conditica is believed to be due to imprcper sizing of transfer bus equi rcent.

Since Unit 1 is in Cold Shutdown, this event had no effect on plant status.

Presently a ceans of limiting the transfer bus leads is being considered and analysis of a final solution is teing pursued.

'I L P. O'REltty

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