PNO-IV-90-028, on 900603,while Attempting to Energize Station Normal Auxiliary Power Transformers,Short Circuit Failure in Bus Works for 25 Kv Sys.Fire Brigade Responded But No Fire Was Reported.Event Under Investigation

PNO-IV-90-028:on 900603,while Attempting to Energize Station Normal Auxiliary Power Transformers,Short Circuit Failure in Bus Works for 25 Kv Sys.Fire Brigade Responded But No Fire Was Reported.Event Under Investigation

ML20198K201
Person / Time
Site:	Columbia
Issue date:	06/04/1990
From:	Morrill P NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:
References
PNO-IV-90-028, PNO-IV-90-28, NUDOCS 9710230187
Download: ML20198K201 (1)

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PRELIMINARY NOTIF"ATION OF EVENT 09 UNUSUAL OCCURRENCE--PNO-V-90-28 Date: 06/04/90 spreliminahnotificationconstitutesEARLYnoticeofeventsofPOSSIBLE b y/,r' J A M I ty or pub 1 interest significance. The information presented is as is11y received without verification or ualuation and is basically all that is known by Region V staff on this dr.te.

Emergency Classification Washington Public Power Supply System WNP-2 Notification of Unusual Event

' Alert M

V Docket No. 50-397 Site Area Emergency Richland, Washington General Emergency h.

~1DINot Applicable g SUSJECT: ELECTRICAL DISTRIBUTION MALFUNCTION WHILE SHUTDOWN j On June 3,1996, at approximately 11:30 am (PDT), while attempting to energize the station normal auxiliary power transformers, a short circuit caused a failure in the bus works for the 25 KV system. The failure led to e iJruption of the bus aanels activation of local fire alarms, and injury to three workers in the area. The unit is currently in cold shutdown conducting an annual maintenance outage.

the station auxiliary transformers The through buses werestepup the main being transfomer, enugized uy "back with feeding"in generator disconnects the ma Theopen.

bus bars had been grounded with ground straps on both sides of the main generator disconnects during the outage. The ground straps had not been removed prior to reenergizini, ?.he bus. Initial assessment by plant management indicate that some confusion arose because the ground straps for the generator side of the disconnect ks were to remain in place while the ground straps for the transformer side of the onnects were to be removed.

Upon energizing the 25 KV bus the ground straps imediately failed. At the same time the short circuit current caused a voltage spike that arced over the lightning arresters located just below the bus ducts. The panel covers were blown off the lightning arresters and the walls of the bus ducts were blown outward. The one inch con per bus straps which connect the lightning arresters to ground were ournt off and ejected from the cabinets. The panel covers struck tcaffolding located next to the panels causing several =caffolding tubes to be deformed. One panel cover and e large assortment of fasteners were found 60-70 feet from their original location.

Three workers who were in the area received minor injuries and were transported to a local hospital for hearing examinations. All three reported some hearing dysfunction due to the noise of the event, p>

The fire brigede responded to the scene, but no fire was reported. There was dp some smoku in the area which quickly dissipated.

Plant management has initiated an investigation into the event. The licensee is preparing a press release. ,,

The resident inspectors responded to the event and are following the h

' licensee's actions, g ,,

n jsinformationiscurrentasof9:00am(PDT) June 4,1990. 4

/ d JTACT: P. Morrill C. Bested FTS 463-3745 (509) 977-2627 {

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e. ',,l k 9710230187 900604 PDR Z 8cE PNO--IV-90-028 PDR

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