ML20244B771
| ML20244B771 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 03/31/1989 |
| From: | Whittier G Maine Yankee |
| To: | Wessman R Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20244B773 | List: |
| References | |
| GDW-89-118, MN-89-42, NUDOCS 8904190402 | |
| Download: ML20244B771 (2) | |
Text
_.
La MaineYankee REUASLE ELECTRICITY FOR MAINE SINCE 127?
l EDISON DRIVE. AUGUSTA. MAINE 04330. (207) 622 4868 March 31, 1989 MN-89-42 GDH-89-118 Director of Nuclear Reactor Regulation United States Nuclear Regulatory Comm13sion Washington, D. C.
20555 Attention:
Mr. Richard H. Wessman, Project Director I-3 Division of Reactor Projects I/II
References:
(a)
License No. DPR-36 (Docket No. 50-309)
Subject:
Maine Yankee Offsite Power Gentlemen:
The purpose of this letter is to transmit the design report for the recently installed 115 kV Capacitor Bank at Maine Yankee and to clarify our position regarding enhancements to the plant's offsite power system.
The enclosed "115 kV Capacitor Bank Design Report" summarizes the design basis, capabilities and planned periodic testing for the capacitor bank that was installed during the 1988 refueling outage to ensure the continued reliability of the plant's off-site power supply. He have reviewed the installation of the capacitor bank and evaluated the results of functional testing. As a result, we have concluded that the capacitor bank is fully operational.
Central Maine Power (CHP) based the 30.6 MVAR sizing of the capacitor bank on load studies which evaluated the Surowiec line voltage with the worst case dynamic load of 55 MVA at Maine Yankee and the steady state lead of 43.45 MVA at Bath and Topsham substations.
The 43.45 MVA assumed the 1988/89 Forcasted Hinter Peak Load and Section 207 Mason out of service. CMP also performed a five year base case model (1993/94 Forecasted Hinter Peak Load) which projected the Surowiec line load of 42.69 MVA at Bath and Topsham substations.
The decrease in Suroweic line load is predicated on load being supplied by additional hydroelectric generttion planned for this area.
These studies by CMP indicate that the capacitor bank will provide adequate voltage support of the Surowiec line for at least the next five years.
Although we believe the offsite power system design meets all applicable regulatory requirements, we have previously indicated our intention to make further enhancements to the offsite power system in order to resolve concerns expressed by NRC staff. Maine Yankee is prepared to install a redundant transformer in parallel to the existing X-14 transformer.
This transformer, sized to carry design station loads without the existing X-14 transformer, should improve the reliability of offsite power and assure the adequacy of the voltage on the 115 kV line even without the capacitor bank.
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MaineYankee United States Nuclear Regulatory Commission Page Two Attention: Mr. Richard H. Hessman HN-89-42 Maine Yankee is evaluating a second enhancement to the electromechanical relays in the auto bus transfer logic.
Should our evaluation prove that replacement of the electromechanical relays would improve the timely transfer of station loads to offsite power in the event of fast clearing electrical faults similar to the August,1988 main transformer fault, then the relays will be replaced.
He are proceeding with the design of the redundant transformer and evaluation of improvements to the auto bus transfer system. He would like to implement the eventual improvements by the end of the spring, 1990 refueling outage. However, prior to installing these changes, we request NRC concurrence that these enhancements will fully resolve NRC's concerns regarding Maine Yankee's offsite power system.
Very truly yours, MAINE YANKEE
})8 hv G. D. Whittier, Manager Nuclear Engineering and Licensing GDH:BJP Enclosure c: Mr. Hilliam T. Russell Mr. Patrick M. Sears Mr. Cornelius F. Holden l
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