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The following event description is based o … The following event description is based on information currently available, if through subsequent reviews of this event, additional information is identified that is pertinent to this event or alters the information being provided at this time, a follow-up notification will be made via the ENS or under the reporting requirements of 10CFR50.73.</br>On October 26, 2006, at approximately 23:53 Mountain Standard Time (MST) a valid actuation of the Palo Verde Nuclear Generating Station Unit 1 Train B Emergency Diesel Generator (EDG) and Unit 3 Train B EDG occurred as a result of undervoltage on their respective safety buses. Both EDGs started and loaded as designed. No Emergency Plan declaration was made and none was required.</br>The loss of power to the two safety buses was the result of an apparent spurious protective relay actuation of Startup Transformer X01 output breakers to Unit 1 NAN-S06 and Unit 3 NAN-S06 busses. Unit 1 NAN-S06 bus was being supplied by its Alternate breaker (1ENANS06F) and Unit 3 NAN-S06 was being supplied by its Normal breaker (3ENANS06C). Prior to the event, maintenance personnel were restoring potential Transformer (PT) fuses at Unit 1 breaker 1ENANS06, Cubicle G. Preliminary information is that the two simultaneous LOP conditions occurred when the outer doors were closed on 1ENANS06, Cubicle G. This condition apparently caused the output breakers of Startup Transformer X01 to open. There was no electrical fault or damage to any electrical components.</br>Both Units 1 and 3 entered Technical Specification LCO 3.8.1 Condition A for one (of two) required offsite circuits inoperable. (The licensee is) proceeding with restoration of Normal offsite power to each safety bus in Units 1 and 3. Once offsite power is restored, the LCOs will be exited and the Unit 1 and 3 train B EDGs will be returned to standby.</br>Both Unit 1 and Unit 3 were at approximately 100% power, at normal operating temperature and pressure prior to and following the EDG actuations. Unit 2 was defueled and was not impacted by the electrical disturbance. No other ESF actuations occurred and none were required. No major equipment was inoperable prior to the event that contributed to the event. The event did not result in any challenges to fission product barriers and there were no adverse safety consequences as a result of this event. The event did not adversely affect the safe operation of the plant or the health and safety of the public.</br>The licensee notified the NRC Resident Inspector.ensee notified the NRC Resident Inspector.
06:53:00, 27 October 2006 +
42,938 +
07:03:00, 27 October 2006 +
06:53:00, 27 October 2006 +
The following event description is based o … The following event description is based on information currently available, if through subsequent reviews of this event, additional information is identified that is pertinent to this event or alters the information being provided at this time, a follow-up notification will be made via the ENS or under the reporting requirements of 10CFR50.73.</br>On October 26, 2006, at approximately 23:53 Mountain Standard Time (MST) a valid actuation of the Palo Verde Nuclear Generating Station Unit 1 Train B Emergency Diesel Generator (EDG) and Unit 3 Train B EDG occurred as a result of undervoltage on their respective safety buses. Both EDGs started and loaded as designed. No Emergency Plan declaration was made and none was required.</br>The loss of power to the two safety buses was the result of an apparent spurious protective relay actuation of Startup Transformer X01 output breakers to Unit 1 NAN-S06 and Unit 3 NAN-S06 busses. Unit 1 NAN-S06 bus was being supplied by its Alternate breaker (1ENANS06F) and Unit 3 NAN-S06 was being supplied by its Normal breaker (3ENANS06C). Prior to the event, maintenance personnel were restoring potential Transformer (PT) fuses at Unit 1 breaker 1ENANS06, Cubicle G. Preliminary information is that the two simultaneous LOP conditions occurred when the outer doors were closed on 1ENANS06, Cubicle G. This condition apparently caused the output breakers of Startup Transformer X01 to open. There was no electrical fault or damage to any electrical components.</br>Both Units 1 and 3 entered Technical Specification LCO 3.8.1 Condition A for one (of two) required offsite circuits inoperable. (The licensee is) proceeding with restoration of Normal offsite power to each safety bus in Units 1 and 3. Once offsite power is restored, the LCOs will be exited and the Unit 1 and 3 train B EDGs will be returned to standby.</br>Both Unit 1 and Unit 3 were at approximately 100% power, at normal operating temperature and pressure prior to and following the EDG actuations. Unit 2 was defueled and was not impacted by the electrical disturbance. No other ESF actuations occurred and none were required. No major equipment was inoperable prior to the event that contributed to the event. The event did not result in any challenges to fission product barriers and there were no adverse safety consequences as a result of this event. The event did not adversely affect the safe operation of the plant or the health and safety of the public.</br>The licensee notified the NRC Resident Inspector.ensee notified the NRC Resident Inspector.
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100 +
00:00:00, 27 October 2006 +
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>.
02:17:48, 2 March 2018 +
07:03:00, 27 October 2006 +
true +
false +
0.00708 d (0.17 hours, 0.00101 weeks, 2.32866e-4 months) +
06:53:00, 27 October 2006 +
Loss of Power to the Unit 1 and Unit 3 Train B Safety Buses with Emergency Diesel Generator Actuation +
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