05000482/FIN-2012008-02
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Finding | |
|---|---|
| Title | Review Startup Transformer Fault Cause |
| Description | When the team left the station, the licensee was still performing troubleshooting activities on the startup transformer to determine the cause of the B phase fault. The licensee tested current transformer (CT) ratios, polarity, and saturation and CT megger tests of the high voltage section were performed on each individual CT. No anomalies were found and troubleshooting and evaluation did not reveal any damage or cause for the fault. The licensee contracted TransGrid Solutions to develop a computer model to further analyze the fault and test failure mode theories related to inrush current and harmonics. The licensee put the startup transformer back into service on February 3, 2012, after concluding that it was safe to restore in order to support further testing. On February 13, 2012, the licensee experienced another fault on the B phase of the startup transformer while attempting to start the A reactor coolant pump. Testing equipment had been installed to monitor the performance of the transformer, and data obtained during the February 13 fault was reviewed. The licensee reevaluated the previous troubleshooting plan to determine additional testing that needed to be performed to determine the cause of the B phase fault. Subsequent troubleshooting identified a short between two unused taps of the high side CTs caused by missing insulation sleeves on wires in the transformer that likely caused the false actuation of the transformers protective relay both times. These wires were associated with providing electrical current indication to the differential current trip circuit. The licensee corrected this condition by restoring the insulation and tested the restored connections by starting all reactor coolant pumps successfully. The NRC will review the final cause assessment for the 345-60 breaker fault, which will be tracked as URI 05000482/2012008-02, Review Startup Transformer Fault Cause. |
| Site: | Wolf Creek  |
|---|---|
| Report | IR 05000482/2012008 Section 4OA5 |
| Date counted | Mar 31, 2012 (2012Q1) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 93800 |
| Inspectors (proximate) | G Replogle J Dixon J Watkins M Baquera M Runyan N O'Keefe N Okonkwoj Dixonj Robles J Watkins M Haire M Runyan N O'Keefe B Correll G Matharu |
| INPO aspect | |
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Finding - Wolf Creek - IR 05000482/2012008 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Wolf Creek) @ 2012Q1
Self-Identified List (Wolf Creek)
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