ML19259D389

Ro:On 791011,analysis Performed Demonstrating That Overvoltage Condition Could Exist on 460-volt Safety Bus Under Extreme Conditions.Caused by Startup Transformer Load of 2.5 MW or Less W/Facility in Shutdown Condition

ML19259D389
Person / Time
Site:	Oyster Creek
Issue date:	10/11/1979
From:	JERSEY CENTRAL POWER & LIGHT CO.
To:
Shared Package
ML19259D387	List: ML19259D386 ML19259D389
References
NUDOCS 7910180411
Download: ML19259D389 (1)

Text

.

Telephone Report Date: October 12, 1979 Date: October 11, 1979 Written Report Date: October 12, 1979 Time: 1115 hours0.0129 days <br />0.31 hours <br />0.00184 weeks <br />4.242575e-4 months <br /> OYSTER CREEK NUCLEAR GENERATIttG STATION FORKlio RIVER, flew JERSEY 08731 Special Report IDEi4TIFICATION: Analysis shows possible overvoltage condition on 460 volt safety bus under extreme conditions.

This event is considered to be reportable as defined in NRC letter dated August 8,1979, re: Adequacy of Station Electric Distributian System Voltages.

DESCRIPTION: An analysis performed pursuant to the NRC letter of August 8, 1979,(Re: Adequacy of Station Electric Distribution System Voltages) shows that under extreme conditions an overvoltage condition could exist on the 460 volt safety bus.

APPARENT CAUSE: Design Procedure Manufacture Unusual Service Condition Installation / Inc. Environmental Construction Component Failure Operator X Other (Specify)

Overvoltage study results ANALYSIS: In order for this event to occur, the Oyster Creek Station would be in the shutdown condition with a load of 2.5 MW or less on the startup transformer. A maximum grid voltage of 238 KV ender these conditions would result in a voltage of 498 volts on the 460 volt bus. Safety related motors on this bus are rated at 440 volts + 10%; therefore, the voltage at the motor would be in excess of the 484 volt maximum. Although the motor would have t xcessive voltage on starting, the voltage would decrease on

tartup of the safety loads.

CORRECTIVE ACTION: Standing Order tio. 24 was issued on May 22, 1979, which requires the operator to maintain the 34.5 KV bus A and B potential voltages between ll4V and ll8V. This provides administrative control to assure that an overvoltage situation will be precluded.

Furthermore, during the upcoming refueling outage, automatic voltage regulators will be installed on the startup transformers to autcmatically control the voltage within acceptable limits.

, r j 3

, , a .) *t moiseW/