ML19210C874

Responds to IE Bulletin 79-23 Re Diesel Generator Field Exciter Transformer Failure Potential.No Neutral Connections Between Exciter Power Transformers & Emergency Diesel generators.Full-load Operational Tests Planned Wk of 791105

ML19210C874
Person / Time
Site:	Point Beach
Issue date:	10/26/1979
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
IEB-79-23, NUDOCS 7911200243
Download: ML19210C874 (2)

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Wisconsin Electnc m cwa 231 W. MICHIGAN. P.O. BOX 2046, MILWAUKEE WI 53201 October 26, 1979 i

Mr . Jame s G . Keppler, Regional Director Office of Inspection and Enforcement, Region III U. S. NUCLEAR REGULATORY COMMISSION -

799 Roosevelt Road Glen Ellyn, Illinois 60137

Dear Mr. Keppler:

DOCKET NOS. 50-266 AND 50-301 REPLY TO IE BULLETIN NO. 79-23 DIESEL GENERATOR FIELD EXCITER POINT BEACH NUCLEAR PLANT IE Bulletin No. 79-23 discussed the potential for failure of the emergency diesel generator field exciter transformer if the neutral of the primary winding of the transformer is connected with the neutral of the generator. Should such a connection exist, high circulating currents could be induced by harmonics. These currents may exceed the transformer ratings and result in damage or failure of the transformer. The Bulletin directed licensees to determine whether such connections exist andto conduct a 24-hour full-load operational test of the emergency diesel generators.

With respect to the first item of the Bulletin, we have inspected both emergency diesel generators installed at the Point Beach Nuclear Plant and have determined that there are no neutral connections betweem the exciter power transformers and the emer-gency diesel generators. These inspections were conducted on September 27 and 28, 1979.

We have also determined that a sustained full-load opera-tional test of the emergency diesel generators, as described in Item 2 of the Bulletin, has not been performed. Although the diesel generators were extensively tested during plant startup, there is no evidence that these tests were conducted over the continuous 24-hour period required by the Bulletin. Therefore, to meet the requirements of the Bulletin, the diesel generators will be tested during the week of November 5, 1979. The test will verify that voltage and frequency requirements are maintained and that the cooling system functions within design limits for the specified 24-hour period.

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(PCT 3 b a 13 / 2 351 7 9112 00 E+3

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g Mr. James G. Keppler October 26, 1979 The emergency diesel generator units installed at Point Beach are GM Electro-Motive Division Model 099-20 units. These units do not specify a two-hour rating, but have a nameplate rating of 3250 KVA continuous and 3575 KVA peaking rating for 2,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> per year. Assuming a power factor of 0.8, the diesel generators have equivalent kw ratings of 2600 and 2860, respectively. These continuous and peak ratings are sufficient to handle the LOCA electrical .oads which are given in the Point Beach Nuclear Plant FFDSAR. Lince the Point Beach emergency diesel generators do not have a specified two-hour rating, the tests will be run for not less than 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br /> at the continuous rating of 2600 kw, followed by two hours at the peaking rating of 2860 kw. We believe this ,

will meet the Bulletin requirements for a sustained full-load operational test.

As stated above, these full-load operational tests will be performed on both diesel generator units during the week of November 5, 1979. The results of these operational tests will, of course, be available for examination by the Office of Inspection and Enforcement.

Very truly yours, t-C. W. Fay, Director Nuclear Power Department Copy to U. S. Nuclear Regulatory Commission Office of Inspection and Enforcement Division of Reactor Operations Inspection Washington, D. C. 20555

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1372 352

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