ML19269F078

Four ROs on 710413,0205,731013 & 740427 Re Partial & Total Losses of Offsite Power.Caused by Wiring Errors & Weather Conditions.No Voltage or Frequency Problems Occurred

ML19269F078
Person / Time
Site:	Point Beach
Issue date:	11/16/1979
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:
References
TAC-12955, TAC-12956, TAC-43944, TAC-43945, NUDOCS 7911300513
Download: ML19269F078 (2)

Text

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Wisconsin Electnc powea couesur 231 W. MICHIGAN, P.o. B0X 2046. MILWAUKEE. WI 53201 November 16, 1979 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U. S. NUCLEAR REGULATORY COMMISSION Washington, D. C. 20555 Attention: Mr. A. Schwencer, Chief Operating Reactors Branch #1 Gentlemen:

DOCKET NOS. 50-266 AND 50-301 LOSS OF 0FFSITE POWER EVENTS POINT BEACH NUCLEAR PLANT Your letter dated October 1,1979 requested that we provide you with information concerning the loss of offsite power which occurred at Point Beach on October 13, 1973 and any other loss of offsite power events. There have been a total of four loss of offsite power events at Point Beach. The following details are provided in response to your request for information:

A. PARTIAL LOSSES OF 0FFSITE POWER

1. Date: April 13,1971 Event: Loss of normal offsite supply to bus lA05.

Cause: Wiring error on relay test switch prevented blocking of undervoltage trip while relay was being tasted.

Results: Diesel generator 3D started and picked up bus lA05.

No other offsite power supplies were affected.

There were no voltage or frequency problems.

Normal power supply was restored a short time later. Them was no effect on the unit since it was shut down at the time.

B. TOTAL LOSSES OF 0FFSITE POWER

1. Date: February 5,1971 Event: Loss of all offsite power and all transmission lines.

Cause: Major ice storm and improper relay operation.

Results: All transmission lines were lost and differential lockout relays on transformers 1X03, 1X04 and 2X04 tripped. Both diesel generators started and picked j up the safeguards loads on Unit 1 which was not on  ?

791130051.3

] ~ Mr. Harold R. Denton, Director November 16, 1979 ee

[ B. TOTAL LOSSES OF 0FFSITE POWER - continued

1. Results: line at the time. One bus on Unit 2 was not picked up because a control power fuse had blown.

Unit 2 was not licensed yet ar.d no fuel had been loaded. The restoration of offsite power to the plant was delayed by the need to evaluate gas sanples from the transformers which had locked out. The outage lasted for 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and 22 minutes. There were no voltage or frequency problems.

2. Date: October 13, 1973 Miit: Loss of all offsite power to safeguare; buses.

Cause: A lightning mast failed and fell on transformer 2X03 while transformer IX03 and the gas turbine generator wem temporarily out of service.

Results : The diesel generators started and supplied power to the safeguards buses of both units. Unit 1 was in hot shutdown and Unit 2 did not trip. The gas turbine generator was returned to service 55 minutes after the event and supplied offsite power to both units for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> and 30 minutes. At that time transformer IXO3 was returned to service. There were no voltage or frequency problems.

3. Date: April 27,1974 Event: Loss of all offsite power to Unit 1.

Cause: A wire lifted in the switchyard control house during a relay modification initiated a breaker failure scheme which isolated 345kV bus section 1.

Results: The isolation of B.S. I removed the power supply to transfonner 1X03, the Unit I high voltage station auxiliary. A fast transfer took place on the 13.8kV bus which would have restored the offsite power to Unit 1, but the 4kV bus under-voltage relays operated before the transfer.

These undervoltage relays trip the connections to offsite power and start the diesel generators.

The buses which were now being supplied by the diesel generators were synchronized to the off-site power supply almost inmediately by the operator and the system was returned to nonnal.

There wem no unit trips, nor were there any voltage or frequency problems.

Very truly yours, C. W. F y, Director Nuclear Power Department

REGULAIURY I r4F0HM A T 10N DISTHiouTION SYSTEM (H10S)

ACCESSIUrd NBH 7911300S13 00C.0 ATE: 79/11/lo NOIAR14ED: rau 00CKET a FACIL:50-doo Point beach Iduclear Plant, Unit 1, nisconsin Electric 050002oo 50-301 Point deacn Nuclear Plant, Unit 2, aisconsin Electric 05000301 AUTH NAME AVIHUN AFFILIAT10N FAY,C.a. Aisconsin Electric Power Co.

H tC I P . .v AME HEC 191ENT AFFILIATION SuoJECT: Four Hos on 710413,0205,761013 4 74042/ re certial 4 total losses of offsite power. Caused by . icing errors 5 weatner conditions.No voitarie or trequency oroolens occurred.

DISTHIbu1 ION CODE: A015S CUPIES H EIvto:LTH 6 /Ei4CL .d. SIZL: M_

TITLE: Onsite Emergency Power Systems 44U T k S : $ % E., ~ .3 CMS ALL m_A]L ,

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