ML20004C837

Submits Clarification of Previous Submittals & Results of Addl Analyses Performed Re Adequacy of Electrical Distribution Sys Per 810326 Request

ML20004C837
Person / Time
Site:	Point Beach
Issue date:	06/01/1981
From:	Burnstein S WISCONSIN ELECTRIC POWER CO.
To:	Clark R, Harold Denton Office of Nuclear Reactor Regulation
References
TAC-12955, TAC-12956, NUDOCS 8106050474
Download: ML20004C837 (5)

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Wisconsin Electnc eam coww 231 W. ?IICHIGAN, P.O. BOX 2046. MILWAUKEE, WI 53201 June 1, 1981 Mr. Harold Denton, Director sN l

Office of Nuclear Reactor Regulation Washington, D. C. 20555 y(3>(gp[\\,.V

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hv U. S. NUCLEAR REGULATORY COMMISSION

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Mr. Robert A. Clark, Chief p'

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Operating Reactor Branch #3

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Gentlemen:

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DOCKET NOS. 50-266 AND 50-301 ADEQUACY OF STATION DISTRIBUTION SYSTEM VOLTAGES POINT BEACH NUCLEAR PLANT, UNITS 1 Ah3 2 Your letter of March 26, 1981 requested additional information relating to the adequacy of the electrical distribution systems at Point Beach Nuclear Plants Units 1 and 2 (PBW). This response provides clarification to our previous submittals and the results of additional analyses performea as a result of your request.

1.

Paragraph Six of your March 26, 1981 letter correctly states that there is no Technical Specification which limits the operation of either or both Units when a single high voltage station auxiliary transform r is out of service. As a result we have completed additional analyses to determine the voltage levels of safety-related equipment assuming the following conditions:

- Heavy Summer Load Conditions The Unit 2 high voltage station auxiliary transformer is out of service. The Unit 2 low voltage station auxiliary transformer supply is transferred to the Unit I high voltage station auxiliary transformer.

- Unit 2 trips while at 100% power due to a accident situation.

All automatically applied accident loads are placed on the safety related busses.

The entire Unit 2 auxiliary load transfers to the Unit 2 low

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t voltage station auxiliary transformer.

3 Unit 1 is shut down from 100% power simultaneously with an accident in Unit 2.

- The entire Unit 1 auxiliary load transfers to the Unit I low voltage station auxiliary transformer. 8106050 g

Mr. Harold Denton, Director June 1,-1981 The load path which was, therefore, assumed is as follows:

345 KV Bus Section 1 Unit 1 High Voltage Station Auxiliary Transformer Unit I and 2 Low Voltage Station Auxiliary Transformers 4160 Volt Busses 1A03, IA04, 2A03, 2A04 Safety-Related 4160 Volt Busses 1A05, 1A06, 2A05, 2A06 4160/480 Volt Transformers ~1X13, IX14, 2X13, 2X14 480 Volt Safeguards Busses 1B03, IB04, 2B03, 2B04 No other sources of offsite power were assumed for this case nor was rny manual load shedding assumed. This analysis resulted in the following voltage levels at points on the load path.

345 KV Bus Section 1 345 KV 100.0%

UNIT 1 High Voltage Station Auxiliary Transformer (High Side) 345 KV 100.0%

(Low Side) 12.56 KV 91.0%

13.8 KV Bus 12.56 KV 91.0%

UNIT 1 and 2 Low Voltage Station Auxiliary Transformers (High Side) 12.56 KV 91.0%

(Low Side) 3.84 KV 92.3%

4160 Volt Busses 1A05, IA06, 2A05, 2A06 3.84 KV 92.3%

4160/480 Volt Transformers IX13,1X14, 2X13, 2X14 (High Side) 3.84 KV 92.3%

(Low Side) 424.0 Volts 88.4%

480 Volt Busses 1D03 424.0 Volts 88.4%

1B04 424.0 Volts 88.4%

i 2B03 424.0 Volts 88.4%

f 2B04 424.0 Volts 88.4%

This would result in a minimum voltage at any safety-related load supplied from the safety-related busses as follows:

IA05 92.2%

2A05 92.2%

1A06 92.2%

2A06 92.2%

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. 1B03 84.2%

2B03 84.2%

1B04 a4.2%

2B04 84.2%

These voltages are lower than those which were calculated for the case submitted.previously, and for which the voltages levels were given in our January 21, 1981 submittal on the same subject. Reference to Paragraphs 9-and 10 of our January 21, 1981 letter will show that the voltages given above are:

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Mr. Harold Denton, Director-June 1, 1981

'As can be seen from the above, the values of. transformer regulation as measured are well below the calculated values.

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_ Contactor Pick up Drop out (Voltage)

(Voltage)

Size 1 72.5%

51.7%

Size IR 72.5%

51.7%

Size 2 70.8%

50.0%

Size 4 70.8%

52.5%.

These values of pick-up and drop-out of safety-related magnetic-

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contactors are well below the minimum voltage expected as a; result of degraded grid voltage conditions.

6.

The adequacy of the electrical distribution system at Point Beach Nuclear Plant is addressed in Section 8.0 of the FFDSAR including a restatement of the General Lesign Criteria which provide the. licensing basis for Point Beach Nuclear Plant.

We trust that this information will allow you to complete your review, with the exception of items -for which we have committed to provide additional information. We would also like to stress the fact that while it is desirable-to supply safety-related loads from the preferred offsite source, and degraded grid voltage may be a legitimate concern, a safety-related redundant relay.

scheme.is.being implemented on each 4160 volt safeguard bus as part of License -

Amendment Nos. 47 and 52 for Units 1 and 2_respectively. The function of this relay scheme is to switch all safety-related loads to an emergency onsite power.

j source if the offsite power supply ~ voltage falls to levels which would prevent operation of, or cause damage to, safety-related equipment.

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Very truly yours, O

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Sol Burstein Execd ive Vice Presideut.

I Copy to NRC Resident Inspector Point Beach Nuclear Plant l

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