ML19291C277

RO 50-219/78-14/3L-0:on 780824,during Plant Shutdown,Power Sources for Auxiliary Electrical Power Sys Did Not Meet Reactor Power Operation Requirements,Causing Breakers to Trip.Cause Under Investigation

ML19291C277
Person / Time
Site:	Oyster Creek
Issue date:	09/22/1978
From:	JERSEY CENTRAL POWER & LIGHT CO.
To:
Shared Package
ML19291C260	List: ML19291C259 ML19291C264 ML19291C266 ML19291C270 ML19291C277 ML19291C282 ML19291C283
References
NUDOCS 8001230263
Download: ML19291C277 (3)

Text

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~ ~ ' - - ' Moms:own, New Jersey 07960 (201) 455-E200 OYSTER CREEK NUCLEAR GENERATING STATION Forked River, New Jersey 08731 Licensee Event Report Reportable Occurrence No. 50-219/78-14/3L-0 Report Date September 22, 1978 Occurrence Date August 24, 1978 Identification of Occurrence Reactor power operation with the power supplies available to the auxiliary electrical power system below that requi red in paragraph 3.7. A of the Technical Specifications. This event Is considered to be a reportable occur-rence as defined in the Technical Specifications, paragraph 6.9.2.b.2.

Conditions Prior to Occurrence The event occurred when the turbine was tripped during a routine shutdown.

Power: Reactor, ~200 MW: .

Electric, O MWe Flow: Reci rculation, 4.8 x 10 5gpm Feedwater, 8.5 x 105 lb/hr Reactor Pressure:

Stack Gas Activity: 1020 1.55 xpsig" 10 pei/sec Description of Occurrence During a routine plant shutdown on August 24, 1978, the power sources for the auxiliary electrical power system did not meet the requirements for reactor power operation as specified in paragraph 3.7. A of the Technical Specifications. When the turbine was manually tripped at approximately 10:21 p.m., all 230 KV circuit breakers opened simultaneously and Isolated the two 230 KV transmission lines from the ring bus in the plant switchyard.

Normally, only the two 230 KV circuit breakers which isolate the generator from the bus would have opened. The first of the tripped breakers necessary to restore the 230 KV power supply was reclosed within one minute of thg trip.

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AITAGECE VI Page 2 of 3 Reportable Occurrence No. 50-219/78-14/3L-0 Page 2 September 22, 1976 Ascarent Cause of Occurrence The cause of the simultaneous trip of the 230 KV breakers is being investigated.

The Relay Department will be monitoring the 230 KV line voltage and current during the next shutdown. Additionally, all switchyard protective relaying will be tested during the outage.

Analysis of Occurrence At the time of the event, the plant auxillary lead was being supplied through the two startup transformers which is normal for a routine shutdown. The isolation of the 230 KV power supply removed one of the two sources for off site auxiliary power. During the brief period of time the 230 KV supply was isolated, the plant auxilia ry power was supplied f rom the 34.5 KV system.

The general objective of the auxiliary power system is to assure an adequate supply of power with at least one active and one standby source of power available for operation of equipment required for safe plant shutdown, to maintain a safe shutdown condition, and to operate the required safety related equipment following an accident. This incident has minimal safety

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sig'Ificance, for with the 230 KV power supply isolated, power for shutdown or engineered safety feature equipment was available from two active sources, 34.5 KV lines, and two standby sources, the diesel generators. Additionally, the duration of the isolation was minimal.

Corrective Action The need for corrective action will be determined af ter the investigation is complete.

Failure Data .

Not applicable.

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ATTACIDETT VI Page 3 of 3 RESPCtiSE 'IO ENCIDSURE CUES"' IONS REPORTABLE OCCURPI:CE 50-219/78-14 Neither Section A or B Enclosure Questions are directly pertinent since the two offsite power supplies were not interrupted. Tne report describes details of the event. For greater clarity sme further details will be given belcw.

Reference to Attachment I, page 1 of 1 indicates hw the offsite pwer supplies are arranged. Ioss of both 230 W feeds to the separate 34.5W buses leaves each 34.5W bus energized through feeds to the 34.5W transmission system. Therefore, offsite pw er was not lost during the event. However, since the Oyster Creek Technical Specifications reqaire both 230W lines to be available, the event constituted a reportable occurrence.

The event occurred on August 24, 1978 and the duration.was less than one minute since breakers were quickly reset and reclosed manually after determining that no real fault was indicated. During this brief period of time there was a sudden excess power f1w on the 34.5KV distribution system. Due to the brevity of duration, voltage levels could not be recorded by Oyster Creek operators. Hwever, since there was no indication of any abnor:ral equipent operation at a time when there was maximum system realignment activities in progress (during normal shutdwn of plant), the voltage drop which may have occurred was considered to be minimal. The effect of the event, therefore, was not one of voltage excursion or system low voltage, but was nore properly described as a transient excess power f1w on the 34.5KV system which was quickly corrected.

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