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At 1444 (CDT) on April 6, 2012, during a p … At 1444 (CDT) on April 6, 2012, during a planned refueling outage on Unit 1, maintenance activities in the high voltage switchyard caused feeder breaker 820 to inadvertently trip. With the second feeder breaker, 924, already out of service, power was lost to the 1B startup transformer. An undervoltage condition was then experienced on the 1G 4160 V emergency bus. As a result, the B1G Sequencer initiated a valid load shed of the 1G 4160 V emergency bus. Due to outage conditions, the B-Train, 1B Emergency Diesel Generator (EDG) was tagged out and did not automatically start but did receive a valid start signal. None of the ESF loads supplied by the 1G bus started automatically since the 1B EDG was out of service. With a B-Train equipment outage in progress, the 1A RHR pump (A-Train) remained in service for shutdown cooling throughout the event. Although the bus safety function was not needed for plant conditions a valid load shed signal occurred and therefore this event is considered reportable.</br>The 1G 4160 V emergency bus was restored to service at 1542 on April 6, 2012. Investigation revealed a technical inaccuracy in the instructions used during the maintenance activity in the high voltage switchyard that caused feeder breaker 820 to trip.</br>The licensee notified the NRC Resident Inspector.ensee notified the NRC Resident Inspector. +
19:44:00, 6 April 2012 +
47,813 +
22:18:00, 6 April 2012 +
19:44:00, 6 April 2012 +
At 1444 (CDT) on April 6, 2012, during a p … At 1444 (CDT) on April 6, 2012, during a planned refueling outage on Unit 1, maintenance activities in the high voltage switchyard caused feeder breaker 820 to inadvertently trip. With the second feeder breaker, 924, already out of service, power was lost to the 1B startup transformer. An undervoltage condition was then experienced on the 1G 4160 V emergency bus. As a result, the B1G Sequencer initiated a valid load shed of the 1G 4160 V emergency bus. Due to outage conditions, the B-Train, 1B Emergency Diesel Generator (EDG) was tagged out and did not automatically start but did receive a valid start signal. None of the ESF loads supplied by the 1G bus started automatically since the 1B EDG was out of service. With a B-Train equipment outage in progress, the 1A RHR pump (A-Train) remained in service for shutdown cooling throughout the event. Although the bus safety function was not needed for plant conditions a valid load shed signal occurred and therefore this event is considered reportable.</br>The 1G 4160 V emergency bus was restored to service at 1542 on April 6, 2012. Investigation revealed a technical inaccuracy in the instructions used during the maintenance activity in the high voltage switchyard that caused feeder breaker 820 to trip.</br>The licensee notified the NRC Resident Inspector.ensee notified the NRC Resident Inspector. +
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Modification date"Modification date" is a predefined property that corresponds to the date of the last modification of a subject and is provided by <a rel="nofollow" class="external text" href="https://www.semantic-mediawiki.org/wiki/Help:Special_properties">Semantic MediaWiki</a>.
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