PNO-IV-98-021, on 980520,loss of Offsite Power Occurred as Result of Fault on Transformer T1A-3,161 Kv to 4 Kv Transformer Which Supplies Power to One of Two Vital Electrical Buses.Special Followup Initiated on 980521
| ML20247P351 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 05/21/1998 |
| From: | Johnson W, Webb Patricia Walker NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| References | |
| PNO-IV-98-021, PNO-IV-98-21, NUDOCS 9805270420 | |
| Download: ML20247P351 (1) | |
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May 21,1998 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-IV-98-021 This preliminary notification constitutes EARLY notice of events of POSSIBLE l
safety or pubfic interest significance. The information is as initially l
received without verification or evaluation, and is basically all that is known by Region IV staff in Arlington, Texas on this date.
Facility Licensee Emeraency Classification Omaha Public Power District X Notification of Unusual Event Ft Calhoun 1 Alert Fort Calhoun, Nebraska Site Area Emergency Dockets: 50-285 General Emergency Not Applicable
Subject:
LOSS OF OFFSITE POWER On May 20,1598, at approximately 2:11 p.m. (CDT), a loss of offsite power occurred as a result of a fault on Transformer T1A-3, a 161 kV to 4 kV transformer which supplies power to one of two vital electrical buses. The 161 kV supply feeder breaker upstream of Transformers T1A-3 and T1A-4 (which was supplying the second vital electrical bus) tripped, resulting in a complete loss of offsite power to the facility. The emergency diesel generators started and loaded onto the vital electrical buses as designed. Shutdown cooling was lost for several seconds as the diesel generators started and restored power to Buses 1A3 and 1A4. The plant had previously been shutdown and was in the 50th day of a refueling outage with the new core loaded, the reactor vessel head installed, the reactor coolant system filled, and shutdown cooling in service.
A Notification of Unusual Event was declared at 2:31 p.m. (CDT). Offsite power was restored to vital Buses 1 A3 and 1A4 by backfeeding through the main transformer with a separate 345 kV offsite power supply at approximately 3:50 p.m., and the Notification of Unusual Event was terminated at 3:57 p.m.
Inspection of Transformer T1 A-3 by the licensee has not, to date, identified any damage to the transformer other than an arc track down the Phase C bushing and between the Phase B and C insulators on the primary side. No cause for the are has been determined, and the licensee is making preparations for restoration of 161 kV power.
The states of Nebraska and lowa have been informed.
Region IV received notification of this occurrence by telephone from the Senior Resident inspector at approximately 2:30 p.m. (CDT), and informed the EDO's office, NRR, and the Office of Public Affairs. A special followup inspection was initiated on May 21,1998.
This information has been discussed with the licensee and is current as of 8:30 a.m. on May 21,1998.
Contact:
W. D. Johnson W. C. Walker (817)860-8148 (402)426-9611
/h 9805270420 980521
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