05000244/LER-2016-001

LER-2016-001, Loss of Station Auxiliary Transformer 12A resulting in automatic start of Emergency Diesel Generator A due to undervoltage signals to safeguards buses 14 and 18.

R. E. Ginna Nuclear Power Plant
Event date:	02-11-2016
Report date:	04-07-2016
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
2442016001R00 - NRC Website

LER 16-001-00 for R. E. Ginna Nuclear Power Plant Regarding Loss of Station Auxiliary Transformer 12A Resulting in Automatic Start of Emergency Diesel Generator A due to Undervoltage Signals to Safeguards Buses 14 and 18

ML16104A029
Person / Time
Site:	Ginna
Issue date:	04/07/2016
From:	Carsky B Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NUREG-1022 LER 16-001-00
Download: ML16104A029 (7)

comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by intemet e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

R. E. Ginna Nuclear Power Plant 05000-244

3. LER NUMBER

2016 - 00

A. PLANT OPERATING CONDITIONS BEFORE THE EVENT:

The reactor was in Operational Mode 1 at 100% power, Reactor Coolant System pressure was 2235 psig and temperature 574 degrees F. The offsite electrical system was in the normal lineup, with each of the two off-site circuits providing power to the four 480 volt safeguards buses via the two station auxiliary transformers. There were no structures, systems or components inoperable at the start of the event which contributed to the event.

B. DESCRIPTION OF EVENT:

On February 11, 2016 at 2305 hours0.0267 days <br />0.64 hours <br />0.00381 weeks <br />8.770525e-4 months <br />, Ginna experienced a loss of off-site power circuit 7T when breaker 52/7T tripped due to Station Auxiliary Transformer 12A failure. Emergency Diesel Generator A started and assumed the loads for safeguards buses 14 & 18. All systems operated as designed. The plant remained at 100 percent power throughout the event.

C. DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES:

February 11, 2016:

• 2305 hours0.0267 days <br />0.64 hours <br />0.00381 weeks <br />8.770525e-4 months <br /> — Operations received indication of loss of off-site power circuit 7T. Emergency Diesel Generator A started and loaded safeguards buses 14 & 18. Station Auxiliary Transformer 12A was determined to be the failed component with indication from overcurrent and differential relays tripped. Technical Specification LCO 3.8.1 was entered.

• 2306 hours0.0267 days <br />0.641 hours <br />0.00381 weeks <br />8.77433e-4 months <br /> - Operators entered Emergency Operating Procedure AP-ELEC.1 for loss of 12A Bus.

• 2325 hours0.0269 days <br />0.646 hours <br />0.00384 weeks <br />8.846625e-4 months <br /> - Operators started Equipment Restoration Procedure ER-ELEC.1 for restoration of off-site power, in order to supply all loads from off-site circuit 767.

February 12, 2016:

• 0032 hours3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br /> - Station Auxiliary Transformer 12A was removed from service and the electric plant was placed in 100/0 lineup. In this lineup, off-site power circuit 767 provides service to all four of the 480 volt safeguards buses via Station Auxiliary Transformer 12B.

• 0052 hours6.018519e-4 days <br />0.0144 hours <br />8.597884e-5 weeks <br />1.9786e-5 months <br /> — Technical Specification LCO 3.8.1 was exited with power to safeguards buses 14 and 18 restored from off-site power circuit 767.

• 0053 hours6.134259e-4 days <br />0.0147 hours <br />8.763227e-5 weeks <br />2.01665e-5 months <br /> - Emergency Diesel Generator A was secured.

• 0127 hours0.00147 days <br />0.0353 hours <br />2.099868e-4 weeks <br />4.83235e-5 months <br /> - Abnormal Operating Procedure AP-ELEC.1 was exited after transferring all loads to off-site circuit 767 via ER-ELEC.1.

comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

• 0351 hours0.00406 days <br />0.0975 hours <br />5.803571e-4 weeks <br />1.335555e-4 months <br /> - Notification of Emergency Diesel Generator A start, event # 51730 was made per 10CFR50.72(b)(3)(iv)(A) February 12-19, 2016:

• Activities performed by the station to replace Station Auxiliary Transformer 12A with a spare transformer.

February 19, 2016:

• 1813 hours0.021 days <br />0.504 hours <br />0.003 weeks <br />6.898465e-4 months <br /> — Replacement transformer energized.

February 20, 2016:

• 0018 hour2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br />s: Operations established the Normal off-site power lineup (two off-site power feeds), as was the pre-event condition, by completing procedure 0-6.9.2.

D. CAUSE OF EVENT

A causal analysis was performed by the station. Electrical testing revealed the cause of the transformer failure appears to be a high side "C" phase to phase internal fault. There was no external damage to the transformer or surrounding area as a result of the fault.

The failed transformer was model Westinghouse serial number RBR-6831 and had been in service for 46 years. There was no indication or warning of impending failure.

The cause of this event per NUREG-1022 Cause Code X, as the failure is attributed to an internal high side fault due to service related insulation degradation.

This event was entered into the site corrective action program (AR 02625128).

An immediate action was performed verifying normal parameters in the remaining transformers. This was completed by reviewing Dissolved Gas Analyzer results for the other transformers. No issues were identified.

E. CORRECTIVE ACTIONS

An on-site spare transformer manufactured by Siemens was placed into service and the unit was restored to normal off-site power lineup.

comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

R. E. Ginna Nuclear Power Plant 05000-244

3. LER NUMBER

2016 - 00

F. SAFETY CONSEQUENCES

Based on the above considerations, this event is not considered to have had any significant effect on the health and safety of the public. The Emergency Diesel Generator A and redundant off-site power circuit with Station Auxiliary Transformer 12B performed as expected.

G. PREVIOUS SIMILAR OCCURRENCES

A review of Ginna LERs submitted during the last five years was completed with the following similar occurrence identified (loss of an offsite circuit resulting in an Emergency Diesel Generator start):

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