ML18136A168

Responds to IE Bulletin 79-23, Potential Failure of Emergency Diesel Generator Field Exciter Transformer. Problems Described Do Not Apply to Emergency Generator Sets at Plants.No Common Connections of Neutrals Exist

ML18136A168
Person / Time
Site:	Surry, North Anna
Issue date:	10/26/1979
From:	Stallings C VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
IEB-79-23, NUDOCS 7911090159
Download: ML18136A168 (4)

Text

e e VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND,V:lBGIN:lA 23261 Octobe~ 26, 1979 . "-*=

o-;

Mr. James P. O'Reilly, Director Serial No. 757/091279A Office of Inspection and Enforcement PO/RMT:baw U. S. Nuclear Regulatory Commission Docket Nos: 50-280 Region II 50-281 101 Marietta Street, Suite 3100 50-338 Atlanta, Georgia 30303 50-339 License Nos: DPR-32 DPR-37 NPF-4 CPPR-78

Subject:

IE Bulletin 79-23 This is in response to IE Bulletin No. 79-23, "Potential Failure of Emergency Diesel Generator Field Exciter Transformer". Our responses for North Anna Power Station Unit Nos. 1 and 2 and Surry Power Station Unit Nos. 1 and 2 are attached.

Very truly yours, L~:. )/ I ~Jlr.r:{i, ;, 'i C. M. Stallings Vice President-Power Supply and Production Operations Attachment cc: Director,.Office of Inspection and Enforcement Division of Reactor Operations Inspection Washington, D. C. 20555

e Attachment page 1 NORTH ANNA POWER STATION RESPONSE TO IE BULLETIN 79-23 POTENTIAL FAILURE OF EMERGENCY DIESEL GENERATOR FIELD EXCITER TRANSFORMER

1. Determine whether or not connections have been made between low KVA rated transformers and high KVA rated EDGs without adequate limitations on the flow of circulating currents. If applicable, provide a description of the corrective action being taken to address this problem.

RESPONSE

Problems as described in IE Bulletin 7-23 do not apply to either of the North Anna Units' 1 and 2 emergency diesel generator sets.

The primary windings of the potential transformer (referred to as excitation power transformer in the IE Bulletin) at North Anna are an "open delta" connection to the generator. No neutral line exists on the high side of the potential transformer.

NAME PLATE DATA Emergency Diesel Generator Mfr.: Fairbanks Morse Model: 38708 1/8 Engine: 12 cylinder, OP turbo-charged diesel Generator: Type TGZDJ Potential Transformers Mfr.: Westinghouse PC-60 Potential, 5 KV Ins. Class Ratio: 35 to 1, 60 Hz Primary volts: 4200/4200 Y Style: 2780A99G02

2. Provide a schedule for the completion of a sustained full-load operation test of the EDGs for a duration of not less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, or provide the results of the similar long duration, full-load test which has already been completed on the EDGs installed for an interval of not less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, of which 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br /> should be at a load equivalent to the continuous rating of the diesel generator and 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> at a load equiva-lent to the 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> rating of the diesel generator. 'The test should also

._-;,_ verify that the voltage and frequency requirements are maintained and that the cooling system functions within design limits.

RESPONSE

A sustained.full-load operation test on the diesel generator for a duration of not less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> has been completed on Unit 2 during preoperational testing. This test was conducted on September 13-14, 1979. The diesel generators were loaded to 3025 Kw for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and 2750 Kw for the re-

e e Attachment page 2 maining 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br />. Test results showed the diesel generators operated satisfactorily with respect to voltage and frequency requirements and that the cooling system functions within design limits.

A sustained full-load operation test on Unit 1 diesel generators will be1 performed prior to cycle 2 start-up. Presently, Unit 1 is undergoing a refueling outage, and both units are undergoing extensive design modifi-cations to their offsite power system. Unit 1 is not expected to return to operation until December 5, 1979.

e 4lttachment page 3 SURRY POWER STATION RESPONSE TO IE BULLETIN 79-23 POTENTIAL FAILURE OF EMERGENCY DIESEL GENERATOR FIELD EXCITER TRANSFORMER

1. Determine whether or not connections have been made between low ~ ~KVA

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~r=-=a:--t~e~d=-:--t~r~a~n=s=f~o~rm;.e_rs_anLhigh-K-VA-rated~EDes--wi-rh-out~equa te limitations on the flow of circulating currents. If applicable, provide a descrip-tion of the corrective action being taken to address this problem *.

2. Provide a schedule for the completion of a sustained full-load operation test of the EDGs for a duration of not less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, or provide the results of the similar long duration, full-load test which has already been completed on the EDGs installed at your facility. The test should demonstrate full-load carrying capability for an interval of not less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, of which 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br /> should be at a load equi-valent to the continuous rating of the diesel generator and 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> at a load equivalent to the 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> rating of the diesel generator. The test should also verify that voltage and frequency requirements are maintained and that the cooling system functions within design limits.

RESPONSE

As directed by I.E.Bulletin 79-23, we have inspected the neutral connec-tions of the EDGs and completed sustained full-load operations on the three EDGs at Surry's Unit Nos. 1 and 2. Utilizing Special Test 58, it was determined that no common connections of neutrals existed. The three EDGs were then operated for a period of not less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> at a full-load of 2750 KW. No problems were experienced during the test. Based on available manufacturer's data, no 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> rating exists on the EDGs.