ML19211C731
| ML19211C731 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 01/08/1980 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8001140361 | |
| Download: ML19211C731 (2) | |
Text
NSIB NORTHERN STATES POWER COMPANY M O N N E A F"O LI S. M IN N E S OTA 5 5 401 January,, 1980 Director of Nuclear Reactor Regulation US Nuclear Regulatory Commission Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PIANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 Loss of Offsite Power Events The following is submitted in response to a letter dated October 1, 1979 from Mr A Schwencer, Chief, Operating Reactors Branch #1, USNRC which requested additional information concerning loss of offsite power events at the Prairie Island Nuclear Generating Plant. The following events represent periods when less than two paths from the grid to the safeguards busses were available.
There have been no other such events.
April 6, 1977 (Ref: License Event Report 77-11 dated May 6, 1977 A.1.
Three circuits are normally available. One circuit was out of service for preventive maintenance when a second was lost.
2.
Personnel error. A relay specialist improperly returned an undervoltage relay to service.
3.
The station auxiliary transformer was not affected by the maintenance being performed. It remained in service supplying all safeguards busses.
4.
No.
5.
No.
6.
31 minutes.
7.
April 6, 1979.
1742 125 B.
Not applicable 8001140 M [
S
NORTHERN STATES POWER COMPANY e
January 8,1980 Page September 12,1978 (Ref:
Lieneses Event Report 78-11 dated September 26, 1980)
A.I.
Three circuits are normally available.
Two circuits were lost.
2.
Lightning strike on 161 kV transmission line.
3.
The 345 kV transmission lines supplying the cooling tower area transformer (source for bus CT11, the third offsite source) were unaffected by the lightning strike.
4.
No. 10 transformer and the 161 kV transmission line breaker to the sub-station 161 kV bus tripped. The 161 kV transmission line breaker was reclosed 8 minutes later. The voltage remained lower than normal (161 kV) until No. 10 transformer was returned to service 35 minutes after the lightning strike.
5.
No.
6.
Degraded voltage existed for 35 minutes.
7.
September 12, 1978.
B.
Not applicable.
Please contact us if you require further information related to these events.
t L 0 Mayer, PE Manager of Nuclear Support Services cc J G Keppler G Charnoff 1742 126