ML19207B114

LER 79-031/01T-0 on 790731:test on Undervoltage Circuitry After Troubleshooting Revealed That Logic A-4 Would Not Operate Due to de-energized Power Supply.Caused by Actuation of Overvoltage Protection Circuit.Actuation Readjusted

ML19207B114
Person / Time
Site:	Calvert Cliffs
Issue date:	08/14/1979
From:	Rizzo P BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19207B111	List: ML19207B110 ML19207B114
References
LER-79-031-01T, LER-79-31-1T, NUDOCS 7908230386
Download: ML19207B114 (2)

Text

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J i ., g p ;s perfon ed i. pr.litig a fault in the LSFAS L'.Wer Vol t:.ge (UV) cir cuitry, follow-up j

4 j.1] l testing ) as baing per ren$ on the UV "A" logic circuit. L'yn discovery _ that. l toj..] lLhe UV "A"-4 1.gic ~old nat initia M, i t .. ;s Acr!..d t ha t le 15 vol t , ' , .c m,,l ias j b.Tra [ to loth the A cnd B UV Actuation cabinet drawers wereide-eneroized_(no voltage ,

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[i li j isupply having been without output was the UV actuation experienced at approximately 1 m 7) [0600 on 7/31/79. This po'..er supply's ovcrvoltage protection circuit was found to l li l 3 ] l have actuated, reducing its output to near 0 VDC. In this condition, no trip 1 '

11141 Lactuation can take place through the UV logic modules it powers. '(This was (CONT.) l 7 8 9 30 F ACitiTY ME THOD OF STATUS  % POWER OTHER STA TUS DISCOVEHY Dl!C,JV ERY OESCHiPTION i s l E l@ l 1 010l@l NA l l45C l@' Operator Observation l 7 8 9 10 12 i) 44 46 AC TIVI TY CONTENT RELEASED OF RELE ASE . AMOUNT OF ACTIVITY LOCATION OF REL. ASE i 6

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F.VE'lT DESCRIPTIC.'1 '"D .3R02/'RE CONSEQUENCES: ONTINUED)

.,, As a cosc y.nce of thcse pc,;er sep,olies ,iing i!e-c. net gizad, the "A" and "d" UV logic ;;euld not' have actuated in the;cvent en initiating sijnal had occurred. Testing had been perfonc.ed at h600 the sac.e corning in which the - -

UV "A"-4 logic "as acte led; it is, therefore, assumed that the d -energization

. . . r. ! :i n the l'; ' cur pcried prior to Oe !!ccc tery cf D .. J a t 1:30 p.m.

'iis is ot a cc .:L i tive ev.:at.

C/:USE DESCRIPTION A.iD CORRECTIVE ACTIONS: (CONTINUED) prov.:n throu,;h tro%ltshooting cn the day of the cvent). The ciervallage protection circuit actuation poin. Jas fourid to be 16 VDC, heretofore considered a reasonably large deviction from the highly regulated nominal gu t, rut voltage. The actuation point has Seen raised to 18 VDC.

It cannot be ascertained that Actual.icn Ch. B UV 15VDC pcwcr /:pply .11 functicr.ed '

concurrently or as a result of the UV Ch. A actuatien. A check of electrical lineups shcwed all lineups norrral. No grounds or evidence of comoning between ESFAS Ch. A and B were discovered. The 120 VAC to Vital Inverters 11 and 12 for synchronization is the cnly common connection between Ch. A and B pcwer trains.

This signal is also corr.on to Vital Inverters 13 and 14, yet no effects were observed to occur on their loads. The overvoltage protection actuation was tested with results similar to Ch. A's power supply. It was also readjusted .

to protect circuits at an output level of 18 VDC.

Further investigation of this event will take the fonn of special testing in order to detennine presence or absence of comnon mode power train disturbances as the result of single bus perturbations.

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