ML19344D163
| ML19344D163 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 03/04/1980 |
| From: | Groce R Maine Yankee |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| WMY-80-36, NUDOCS 8003110448 | |
| Download: ML19344D163 (4) | |
Text
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ENGINEERING OFFICE WESTBORO, M ASS / CHUSETTS 01681 N\\
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% cm - m O B.3.2.1 March 4, 1980 WMY 80-36 United States Nuclear Regulatory Commission Was hington, D. C.
20555 Attention:
Office of Nuclear Reactor Regulation Operating Reactors Branch 14 Division of Operating Reactors
References:
(a)
License No. DPR-36 (Docket No. 50-309)
(b)
USNRC Letter to MYAPC dated November 27, 1979 (c) MYAPC letter to USNRC WMY 79-14 dated March 2,1979
Subject:
Loss of Offsite Power Survey
Dear Sir:
As requested in Reference (b), m are providing the following info'rmation.
We have reviewed Maine Yankee Plant experiences with the offsite power system and find no occurrences of complete or partial loss of offsite power during the eight years of plant operation (1972 to present).
Offsite power for the Maine Yankee Plant is supplied from a 115 kV switchyard adjacent to the plant. Two 115 kV trammission lines, one from Mason Station and one from Suroweic Substation supply the llL kV switchyard.
Both Mason Station and Suroweic Substation are extensively interconnected with the 115 kV and 345 kV transmission nethork in the New England area. Each station has a 345 kV/115 kV automatic load tapchanging autotransformer which maintains station voltage at approximately 120 kV.
Transmission line interconnections are shown on Figure 1.
Upon loss of their normal power source, the station auxiliary buses are automatically transferred to reserve station service trancformers X14 and X16. Transformers X14 and X16 supply power from the 115 kV switchyard to the 4160 volt and 6900 volt buses respectively. A one line diagram of the Maine Yankee auxiliary power system is attached as Figure 2.
As long as at least one of the two 115 kV transmission lines is energized from the remote end of the line, the 115 kV switchyard at Maine Yankee is energized and offsite power is available to the plant loads. During the eight years of plant operation there have been individual 115 kV line outages for maintenance and brief outages caused by lightning or by line faults, but there has never been a simultaneous outage of both 115 kV transmission lines.
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United Stst0c Nuclsar RegulGtory Commisalon March 4, 1980 Offic2 of NuclOSr R :ctor RegulatiCn Paga 2 When one of Maine "ankees' half-size main transformers failed on Augus t 31, 1978, the automatic transfer to the offsite power source was automatically blocked due to the transient low voltage on the 115 kV bus caused by the transformer fault.
Reference (c), provided our evaluation of this event. Maine Yankee does not consider this event a loss of offsite power since the system voltage recovered immediately with isolation of the faulted transformer and the operator manually connected the offsite pou.r source approximately one minute af ter the automatic transfer was blocked.
We trust that you find this information satisfactory; however, should you desire additional information, please contact us.
Very truly yours, MAINE YANKEE ATOMIC POWER COMPANY Robert H. Groce Senior Engineer - Licensing HWI/ dis Attachments
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