ML20086B384

Forwards Proposed Rev to Circuit Drawing E-1203 Re Undervoltage Relay Parallel Contact Path.Prompt Approval Requested

ML20086B384
Person / Time
Site:	Fort Saint Vrain
Issue date:	08/19/1974
From:	Walker R PUBLIC SERVICE CO. OF COLORADO
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20086B380	List: ML20086B384 ML20086B401 ML20086B414 ML20086B419
References
NUDOCS 8311170184
Download: ML20086B384 (3)

Text

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l \\s- P. O. Tm 361, riatteville, Colorado 80651

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Auo,us t 19, 3974 Docket 1:o. 50-267 Mr. A. Cicnbusso, Deputy Director ,

Renetor Proje ets Dircetorate of Licenning United State: Atomic rnergy Ccr.::ission Uachington, D. C. 20S45

Dear lir. Cia.?busso:

Subj cet : Revised Electrical Circuitry As reported in Abnormal occurrence. Report No. 15, a singic failure occurred in the centrol circuitry that prevented auto:ntic load sequcucing onto both diesel-gennrators, during a Technical Specification Survei13nnce test. A revfeu of t % circuitry den 171 revealed that due to the fa-!1ure of cu>:lliary contacts 21 am) 22 to opere.te preptrly in brcaher 252 DGin, Drateing 1:o. L-1203, page 20, attached, essentir.1 bur load shedding failed to take place which prevented all four lond sequencing progene. ors f ront functioning.

To clinir :te this deficiency in the design wo vauld propese the addition of a parallel contact path, the contacts driven by voltage sensitive relays, which coultor the l,80 volt eccential bus voltsgc. This contact logic is shova in red on Drawing ro. E-1203, page 20 and 21, Issuc F, attached.

The proposed Under Voltage Relays vould ut ilim a 5 recond TDC to accure they did not opercte during a synten voltage disturbance due to lightning, trans-nisalon J .ine trouble, etc. The five saccal TDC vould also nasara operation of the Lead Shedding Relayn prior to the Diesel-generators starting and coming to spred and voltage, which taLea appwximately 12-15 seconds.

In conversationa uith the Staff, ve have been requested to subnit the proposed circuit revision to tha:a for revicw and approval.

Uc would appreciate app'roval as quickly .:n possikile so ve may implement the revision to clininate this potcatial comon code failure.

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Very truly yours, dd #

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8311170184 741209 PDR ADOCK 05000267 7 7' (U "- h#

b PDR R. F. Malher

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Vice Frenident Engineering,and Planning <

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