ML19274F816

LER 79-048/01T-0 on 790719:w/reactor Shut Down for Refueling,Overcurrent Trip Devices in Supply Breakers for Reactor Bldg Motor Control Ctr Were Found to Be 300 Amp Instead of 600 Amp.Caused by Personnel Error

ML19274F816
Person / Time
Site:	Hatch
Issue date:	07/30/1979
From:	Coggin C GEORGIA POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19274F814	List: ML19274F813 ML19274F816
References
LER-79-048-01T, LER-79-48-1T, NUDOCS 7908060474
Download: ML19274F816 (3)

Text

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! occurred. The busses have not been inoperable because of the 300 amp

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Georgia Power Company Plant E. I Hatch Baxley, Georgia 31513 Event Description and Probable Consequences (Continued) trip devices at anytime since initial energization. This is not a repeti tive occurrence. Public health and safety were not affected by this incident.

Cause Description and Corrective Actians (Continued) returned to service. The 600V breakers in both Unit 1 and Unit 2 have been checked and were found to contain the correct size trip devices.

Narrative Sumary LER 1-79-48 E,3._ " nit 1 was shut down for refueling, routine preventative maintenance was being performed on 600V AK-25 circuit breakers.

On 7-19-79, it was found that the supply breaker trip device for the reactor building 600/208V essential motor control centers IC (01VII R24-5012) were 300 ampere instead of 600 ampere as designed.

Trip devices are interchangeable on these breakers so it is possible to change trip settings by changing trip devices.

A check of documentation revealed that these were the original breakers with 300 amp trip devices that were preoperationally tested and engerized in May 1973. Further checking revealed that originally the design had calle for 300 amp trip devices and a drawing change prior to the preoperational test had changed these to 600 amp. This was in conjuction with an enlargement of the motor control center. When the motor control centers were preoperationally tested and energized in 1973, personnel failed to detect a drawing change and 300 breakers were left installed.

This error affects both divisions of the AC distribution system in the reactor building. Th' affected motor control centers are classified as "e ssenti al . " Neither motor control center has been inoperable because of the error at any time since initial energization. It has not been detennined whether an actual overload trip problem due to a heavily le:ded bus or many simultaneous motor starts or a breaker trip coord-inaticn problem existed during this time; however, as previously stated no prcalem was encountered during preoperational or startup testing or several years of operation. The correct breaker trip devices are now instailed and no further action is deemed necessary.

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