ENS 52769: Difference between revisions
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StriderTol (talk | contribs) (Created page by program invented by StriderTol) |
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| event date = 05/23/2017 23:30 EDT | | event date = 05/23/2017 23:30 EDT | ||
| last update date = 05/24/2017 | | last update date = 05/24/2017 | ||
| title = All Four Edgs Autostarted During Transfer | | title = All Four Edgs Autostarted During Transfer of Shutdown Board to Normal Power Source for Unit 2 Testing | ||
| event text = On May 23, 2017 at 2330, while transferring 2A-A 6.9 kV Shutdown Board from its alternate power source to its normal power source in support of outage testing, a failure occurred which resulted in the loss of the Shutdown Board, emergency start of all 4 Emergency Diesel Generators (EDGs), and required the manual emergency stop of 2A-A EDG. | | event text = On May 23, 2017 at 2330, while transferring 2A-A 6.9 kV Shutdown Board from its alternate power source to its normal power source in support of outage testing, a failure occurred which resulted in the loss of the Shutdown Board, emergency start of all 4 Emergency Diesel Generators (EDGs), and required the manual emergency stop of 2A-A EDG. | ||
During transfer of the 2A-A 6.9kV Shutdown Board, the hand switch for the normal feeder breaker on the shutdown board was being maintained in the 'CLOSE' position while the alternate feeder breaker hand switch was placed in 'TRIP.' As expected, the alternate feeder breaker opened and the normal feeder breaker closed. However, the upstream supply breaker to the normal feeder breaker immediately tripped due to an overcurrent relay actuation on a single phase. As a result, the 2A-A 6.9 kV Shutdown Board deenergized, initiating a blackout signal which started all 4 of the station's EDGs. During board stripping (opening of all feeder and load breakers, to prepare the board for automatic reenergization from the EDG), the normal feeder breaker to the Shutdown Board failed to trip. This failure to trip prevented the emergency feeder breaker in the output of 2A-A EDG from closing, in accordance with interlock logic. As a result, 2A-A 6.9 kV Shutdown Board remained deenergized which prevented the cooling water supply valve for the EDG from opening due to loss of motive power. This lack of cooling caused operators to emergency stop the 2A-A EDG. | During transfer of the 2A-A 6.9kV Shutdown Board, the hand switch for the normal feeder breaker on the shutdown board was being maintained in the 'CLOSE' position while the alternate feeder breaker hand switch was placed in 'TRIP.' As expected, the alternate feeder breaker opened and the normal feeder breaker closed. However, the upstream supply breaker to the normal feeder breaker immediately tripped due to an overcurrent relay actuation on a single phase. As a result, the 2A-A 6.9 kV Shutdown Board deenergized, initiating a blackout signal which started all 4 of the station's EDGs. During board stripping (opening of all feeder and load breakers, to prepare the board for automatic reenergization from the EDG), the normal feeder breaker to the Shutdown Board failed to trip. This failure to trip prevented the emergency feeder breaker in the output of 2A-A EDG from closing, in accordance with interlock logic. As a result, 2A-A 6.9 kV Shutdown Board remained deenergized which prevented the cooling water supply valve for the EDG from opening due to loss of motive power. This lack of cooling caused operators to emergency stop the 2A-A EDG. | ||
Latest revision as of 21:42, 1 March 2018
| Where | |
|---|---|
Sequoyah  Tennessee (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| LER: | 05000327/LER-2017-002 |
| Time - Person (Reporting Time:+0.67 h0.0279 days <br />0.00399 weeks <br />9.17766e-4 months <br />) | |
| Opened: | Robert Camenisch 04:10 May 24, 2017 |
| NRC Officer: | Steve Sandin |
| Last Updated: | May 24, 2017 |
| 52769 - NRC Website
| |