ML20147A332
| ML20147A332 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 07/07/1980 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1980-022-00 | |
| Download: ML20147A332 (4) | |
Text
Accession Number: 159134 e: July 7, 1980 Loss of Offsite Power at Arkansas Nuclear I failure sequence was:
With the unit at 100% power, switchyard circuit breakers tripped apparently due to a ground fault, isolating the Mabelvale 500 kV line. Unit 2 and Unit 1 generation was transferred to the Fort Smith 500 kV line. (The Mayflower line was out of service.)
The Fort Smith 500 kV line tripped open at the Fort Smith and due to feeder overload. (The Mabelvale line became available but failed to close onto the ring bus because of a lack of synchonization.)
The Morrilton East 161 kV line tripped on overload, leaving only Unit I generator output feeding the auto transformer and the Russellville East line carrying Unit 1 power generation. Startup transformer No. 1 remained energized from the autotransformer and startup transformer No. 2 remained tied to the 161 kV bus.
A manual runback was initiated following an automatic generator runback. The reactor subsequently tripped.
Auxiliary loads were transferred to startup transformer No. 1, which was already experiencing low output voltage.
The autotransformer bank locked out due to a faulted relay, locking out startup transformer No. 1 and Unit 2 startup transformer No. 3.
This resulted in a loss of all auxiliary bus voltage.
The unit diesel generators started and provided power to safety-related loads. (Power remained available by manual transfer from startup transformer No. 2.)
rective action:
Approximately 65 minutes later house loads were transferred to tup transformer No. 1.
ign purpose of failed system or component:
Offsite power provides the preferred source of power to safety re-d loads when the unit generator is unavailable.
trip former #I former #1 provide (which was lockout (loss power to already experi- of voltage on safety-encing low all auxiliary related output voltage) buses) loads No No - turbine-driven AFW train available for core cooling No No No 4 - Actual Occurrence for Loss of Offsite Power at Arkansas Nuclear I
House Loads No 1 No 2 No 3 Yes 4 Yes 5.
No 6 (F)
No 7 Yes 8 Yes 9 No 10 Yes II No 12 Yes 13 NSIC 159134 - Sequence of Interest for Loss of Offsite Power at Arkansas Nuclear - Unit 1
C ACCESSION NUMBER: 159134 NO.: 80-022 E OF LER: July 7, 1980 E OF EVENT: June 24, 1980 TEM INVOLVED: Offsite power PONENT INVOLVED: Transmission lines, relay SE: Sequential loss of transmission lines due to ground fault and overload, transformer lockout due to unspecified relay fault.
UENCE OF INTEREST: Loss of offsite power UAL OCCURRENCE: Loss of offsite power CTOR NAME: Arkansas.Nuclear 1 KET NUMBER: 50-313 CTOR TYPE: PWR IGN ELECTRICAL RATING: 850 MWe CTOR AGE: 5.9 years DOR: Babcock & Wilcox CHITECT-ENGINEERS: Bechtel RATORS: Arkansas Power and Light ATION: 6 miles NW of Russellvile, Arkansas RATION: N/A NT OPERATING CONDITION: 100% power E OF FAILURE: Made inoperable COVERY METHOD: Operational event MENT: See NSIC 159136 (Arkansas Nuclear 2, 50-368, LER 80-042, July 7, 1980).