05000281/LER-2013-001
| Surry Power Station, Unit 2 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 2812013001R00 - NRC Website | |
1.0 DESCRIPTION OF THE EVENT At 08:03 on December 29, 2012, with both Unit 1 and Unit 2 operating at 100%, the supply breaker [EIIS-EA-BKR] to the B reserve station service transformer (RSST) [EllS-EA-XFMR] tripped open on an instantaneous over-current of the B and C phases due to a pelican contacting the overhead lines from the switchyard to the B RSST. This resulted in a lockout of the B RSST and loss of power to the E transfer bus [El IS-EA-BU] and the Unit 2 H emergency bus [EllS-EA-BU] from its normal off-site power supply. An under-voltage automatic start signal was generated, and emergency diesel generator (EDG) 2 [El IS-EK-GEN] started and loaded on the Unit 2 H emergency bus as designed.
All equipment performed as expected during the event, and there were no unexplained occurrences.
Visual inspections verified there was no damage to the lines, supply breaker, or B RSST. The E transfer bus was reenergized at 12:23, and the normal source of power was restored to Unit 2 H emergency bus at 12:42. EDG 2 was returned to automatic control at 15:18. All electrical distribution systems were restored to a normal alignment.
At 15:21, an event notification was made to the NRC for the EDG 2 actuation in accordance with 10 CFR 50.72(b)(3)(iv)(A). This report is also being submitted, pursuant to 10 CFR 50.73(a)(2)(iv)(A), for automatic actuation of EDG 2.
2.0 SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS The event was uncomplicated, with no equipment failures. Equipment performed as expected. EDG 2 started and restored power to the 2H bus as designed. Sufficient alternate sources of power were available, including the swing EDG and the station blackout diesel. This event is considered to be of low safety significance. As a result, the health and safety of the public were not affected.
3.0 CAUSE The overhead lines extending from the switchyard to the B RSST traverse over the intake canal. A pelican observed in the canal flew up into the lines and contacted the B and C phases.