ML19322E610

LER 80-011/01T-0:on 800312,investigation of Onsite Power Distribution Sys Revealed Voltage of Some 480-volt Loads Below Min Allowable W/Min Grid Voltage & Worse Case Loading. Caused by Incomplete Analysis When Transformers Replaced

ML19322E610
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	03/26/1980
From:	Murphy W VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19322E606	List: ML19322E605 ML19322E610
References
LER-80-011-01T, LER-80-11-1T, NUDOCS 8004010499
Download: ML19322E610 (1)

Text

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LICENSEE EVENT REPORT LER 80-11/1T CONTQOL BLOCK: l 1

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(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h IoIal l Investigation of the on-site power distribution system revealed that the voltage of l I o I a i l some 480V loads is slightly below minimun allowable with minimum grid voltage and [

lo I4 l l worst case loading. The investigation also showed the 4160V system voltage to be l IoIsl l slightly higher than allowable with maximum grid voltage and light loading. Since [

lo le l l these conditions exist only with the plant in closed cycle cooling mode or cold l 10171 l shutdown, the possible consequences to the public health and safety are minimal. l l

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41 I44 Z l 919191@ 47 33 J4 34 36 31 40 42 43 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS I1 IoiI The cause of this occurrence was an incomplete analysis ef the on-site power dis- l l1 Iil I tribution system when the startup transformers were replaced. By changing taps on I li12l l startup transformers T-3A and T-3B and on 4160/480V transformers T-8 and T-9, the l L' L.J l potential concerns will be corrected. Ref. "YAEC Report #1205, Aux. Power System [

t 4 l Voltage Study for VY Nuclear Power Station." l 7 8 9 80 ST S  % POWER OTHER STA TUS IS O RY OBSCOVERY DESCRIPTION 32 Ii' l51 dh l ol 9 l 91@l NA l lDl@l NRC Letter dated August 8, 1979 l ACTIVITY Co$ TENT RELE ASED OP RELE ASE AMOUNT OF ACTIVITY LOCATION oF RELEASE

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I NAME OF PREPARER W. P. Murphy P E:

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