ML19211A183

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Responds to IE Bulletin 79-23, Potential Failure of Emergency Diesel Generator Field Exciter Transformer. Problem Not Applicable to Facility.Flow of High Circulating Current Cannot Exist at Plant
ML19211A183
Person / Time
Site: Beaver Valley
Issue date: 10/24/1979
From: Dunn C
DUQUESNE LIGHT CO.
To: Grier B
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
IEB-79-23, NUDOCS 7912170164
Download: ML19211A183 (2)


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October 24, 1979 United States Nuclear Regulatory Commission Attention: Boyce H. Grier, Director Region I 631 Park Avenue King of Prussia, Pennsylvania 19406

Reference:

Beaver Valley Power Station, Unit No. 1 Docket No. 50-334 License No. DPR-56 Response To IE Bulletin 79-23

Dear Mr. Grier:

We have reviewed IE Bulletin No. 79-23 concerning the potential failure of emergency diesel generator field exciter' transformers. It is our conclusion the problem is not applicable at Beaver Valley Power Station.

At Beaver Valley, the neutral of the emergency diesel generator is ungrounded in the normal and emergency modes of operation. The neutral of the generator is not connected to the neutral of the primary winding of the excitation power transformer (EPT) and the primary winding of the EPT is not grounded. As such, the flow of high circulating current described in the Bulletin cannot exist. In the exercise mode of operation, the neutral of the diesel generator is connected to ground through a ten (10) ohm resistor to limit the flow of ground fault currents. The connection of the generator's neutral to the ten ohm resistor to ground is made through a motor operated switch. The switch is administrative 1y controlled to be open except in the exercise mode of operation. The position of the motor operated switch is indicated in the control room. However, as noted above, the neutral of the generator is not connected to the EPT and the neutral of the primary winding of the EPT is not grounded. As such, the connection of the neutral to ground through the ten ohm resistor will not result in the flow of high circulating currents between the neutral of the generators and the EPT.

The neutral of the primary winding of the EPT is connected to the primary winding of the diesel generator potential transformers. This connection is not grounded. This connection wss reviewed by Duquesne Light Engineering and by the manufacturer of the Beaver Valley emergency diesel generator units, Electro-Motive Division of General Motors Corporation. The Electro-Motive Division stated that the configuration in use at Beaver Valley is recommended to stabilize the voltage difference. Electro-Motive Division stated that this connection would not result in unacceptable circulating currents.

1593 272 79121701 6

Beaver Valley Power Station, Unit No. 1 Docket No. 50-334 Response To IE Bulletin 79-23 Page 2 Based on the above, we conclude that the present connections of the emergency diesel generators at Beaver Valley Power Station are proper and will not result in a flow of high circulating currents during operation with the neutral of the diesel generator grounded through the ten ohm resistor.

We plan to perform a 24-hour full load diesel generator test during the month of January, 1980. The unit will be in cold shutdown for refueling at this time.

Very truly yours, C. N. Dunn Vice President, Operations cc: United States Nuclear Regulatory Commission Office of Inspection and Enforcement Division of Reactor Operations Inspection Washington, D. C. 20555 1593 273