ML19291C270

RO 50-219/78-03/3L-0:on 780214,startup Transformer Lockout 865A Alarm Annunciated in Control Room.Caused by Fault in Cable.Cable Standoffs Inspected,Cleaned & Varnished. Evaluation Being Performed on Cable

ML19291C270
Person / Time
Site:	Oyster Creek
Issue date:	03/15/1978
From:	JERSEY CENTRAL POWER & LIGHT CO.
To:
Shared Package
ML19291C260	List: ML19291C259 ML19291C264 ML19291C266 ML19291C270 ML19291C277 ML19291C282 ML19291C283
References
NUDOCS 8001230254
Download: ML19291C270 (3)

Text

ATI; m E E V Page 1 of 3 OYSTER CREEK i;UCLEAR GEtiEU.TitJG STATIOri Forked River, tiew Jersey Oc731 Licensee Event Report Reportable Occurrence tio. 50-219/78-03/3L-0 Report Date March 15, 1978 Occurrence Date February 14, 197'8 Identification of Occurrence Trip of startup transformer bank 5 caused the auxiliary power system to be operable in a degraded mode.

This event is considerec to be a reportable occurrence as defined in the Technical Specificatiens, paragraph 6.9.2.b.2.

Conditions Prior to Occurrence The major plant parameters at the time of the occurrence were:

Power:

Reactor, 1844 MWt Electric, 647 MWe 4

Flow:

Recirculation, 14.6 x 10 gpm Feedwater, 6.895 x 106 lb/hr Stack Gas:

4.05 x 10" uci/sec Description of Occurrence On February 14, 1978, at approximately 1130 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.29965e-4 months <br />, the "startup transformer lockout 86SA" alarm annunciated in the station control room.

A burn hole was detected in the cable bus duct.

Further investigation revealed that the tap off of bank 5 to dilution main breaker had an insulation failure between B phase and ground at the support for the splice connector.

Apparent Cause of Occurrence The cause of the occurrence was attributed to a fault in the cable.

Analysis of Occurrence The normal auxiliary power supply for the plant is provided by a transformer directly connected to the 24 KV generator.

Startup power and standby auxiliary power is provided by two transformers supplied f rom separate 34.5 KV buses in the switchyard.

The buses are connected through a circuit breaker which will open automatically if either _ bus is faulted.

Therefore, it is unlikely that pcwer line catcces or equjpmen; failures will cause an interruption to the station's standby auxiliary power.

Either of the two

~

1792 214 230 O#f oqoa a 1 %mL o oyw 8001

ATIAGEir V Page 2 of 3 Renartable Occurrence io. 50-219/73-03/?L-0 Page 2 March 15,1973 startup transformers is more than arple to carry the energency au>;ilicry power Icad.

The safety tignificance of this event is considered to be minir.al since during this period redundant power supply from bank 6 was available.

The auxiliary pc..er system was still considered operable with the loss of bank 5 but in a degraded mode.

Corrective Action The insulation failure between B phase and ground at the support for the splice connector was taped according to normal taping procedure.

Cable stand-offs affected by the fault were cleaned and varnished and all standoffs in the area were inspected.

An evaluation is being performed on the cable to determine whether further action is required.

Failure Data it is suspected that a similar undetected fault in this cable was responsible for the 1-C bus trip which occurred on July 28, 1977.

(See Reportchle Occurrence tio. 50-219/77-17/3L.)

1792 215

A'I"lACH'E.'r V Page 3 of 3 RESPCr!SE 'IO ENCIDS~.3E CfESTIO::S REPORTABLE OCCURRC C 53-219/78-3 Secticn A of Enclosure Qaestions is pertinen: since this event involved only one Startup Transformer.

RESPONSE

A.1 'Iko circuits are available; one was lost.

A.2 Cause was ground fault on B phase of cable bus.

A.3 Degradation of cable bus was more advanced in the Bank 5 Cable Bus.

A.4 No voltage excursions are relevant to this event.

A.5 lb frequency excursions are relevant to this event.

A.6 hhile repairs were being made the Bank 5 cable bus was out of service appw.. 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

A.7 Ihte of Event: 2/14/78 1792 216