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| Entered date | Event description | |
|---|---|---|
| ENS 41945 | 25 August 2005 02:23:00 | 4160 volt Bus 1D normal supply Breaker 1D tripped open. The associated No. 2 EDG automatically started and is supplying the 1D 4160 volt Bus. Plant equipment responded as expected. Troubleshooting is in progress to determine the cause of the breaker trip. The licensee notified the NRC Resident Inspector. |
| ENS 41741 | 1 June 2005 23:12:00 | The licensee reported that an offsite electrical transient on the 230KV transmission line appears to have caused a generator trip and corresponding turbine trip and reactor scram. The scram was uncomplicated. All rods fully inserted. No safety relief valves lifted during the transient. The reactor is stable at 920 psi with decay heat being discharged to the main condenser and fed via the main feed pumps. There was no loss of offsite power during the transient and the plant is in a normal electrical lineup. The specific cause of the generator lockout is still under investigation but is believed to have been caused by maintenance work at the Manitou 230KV substation about 25 miles from the plant. Lightning arrestors were being placed in service at the substation and are believed to have resulted in an electrical disturbance on the grid. The licensee notes that switchgear for the stack lighting did trip during the transient and so the FAA was notified on the stack lighting outage. The licensee plans to remain in hot shutdown for approximately 24 hours before restart. The licensee notified the NRC Resident Inspector. |