ML19211A789

Forwards Response to IE Bulletin 79-23 Re Failure of Emergency Diesel Generator Field Exciter Transformer.No Circuit Connecting Generator Ground & Exciter Primary Transformer.Special Test Procedure 58 Completed 791103

ML19211A789
Person / Time
Site:	Duane Arnold
Issue date:	11/08/1979
From:	Root L IES UTILITIES INC., (FORMERLY IOWA ELECTRIC LIGHT
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
IEB-79-23, NUDOCS 7912200683
Download: ML19211A789 (3)

Text

,. . _

Iowa Electric Light and Pbwer Company November 8,1979 LDR-79-286 LARRY D ROOT 7ES7cNin"$5

• 2r - b:.l Mr. James G. Keppler, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Region III 799 Roosevelt Road Glen Ellyn, IL 60137

Subject:

Potential Failure of Emergency Diesel Generator Field Exciter Transformer

Reference:

IE Bulletin No. 79-23 File: A-101a

Dear Mr. Keopler:

Please find attached our response to IE Bulletin 79-23.

We trust this submittal completely addresses your concerns.

Very truly yours, S.

Larry D. Root Assistant Vice President Nuclear Generation LOR /JC Z/ms Attach.

cc: U.S. Nuclear Reculatory Commission Office of Inspection and Enforcement Division of Reactor Ocerations Inscection Washington, D.C. 20555 D. Arnold

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w DUANE ARHOLD ENERGY CENTER Response to NRC IE Bulletin No. 79-23 Item No. 1 Determine whether or not connections have been made between low KVA rated transfonners 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

The excitation system of the Fairbanks-Morse diesel generator at the DAEC utilizes an ungrounded open Delta excitation primary side potential transiormer configuration. The generator is a grounded " wye" configured source. There is no circuit connecting the generator ground and the exciter primary transformer. By design, this system will only pass low frequencies from phase to phase, which in turn will cancel each other out. Therefore, low frequency harmonics present in the system will cancel without producing undesirable high circulating currents that could damage the exciter primary transformer.

Item No. 2 Provide a schedule for the completion of a sustained full-load operation test of the EDG's 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 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 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

DAEC Special Test Procedure No. 58, Rev. 0, " Standby Diesel Generator 24 Hour Continuous Operational Testing", was performed to verify the full-load carrying capability of both EDGs. - Testing was conducted for one EDG at a time. Each EDG was continuously loaded for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />; 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br /> at a load equivalent to the continuous rating of the generator (2850 KW), 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 generator (3135 KW). The following parameters were monitored on a hourly basis throughout the test runs:

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-- Current

-- Frequency

-- Voltage Coolant Casing Temperature

-- Power Factor

s. .

2 Special Test Procedure No. 58 was completed on 11-3-79. All acceptance criteria were met. No abnormalities in any of the above parameters were observed. Therefore, it is concluded that the CAEC Emergency Diesel Generators are capable of performing their intended design function.

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