ML20211N466

Informs of Plans to Install New 2,400-volt Circuit Breaker During May 1987 Outage to Connect Station Svc Transformer 4 Directly to 2,4000-volt Bus 1.Installation Will Alleviate Concerns Re HPSI Pump & Transformer Loading

ML20211N466
Person / Time
Site:	Yankee Rowe
Issue date:	06/19/1986
From:	Haseltine J YANKEE ATOMIC ELECTRIC CO.
To:	Mckenna E Office of Nuclear Reactor Regulation
References
DCC-86-072, DCC-86-72, FYR-86-056, FYR-86-56, NUDOCS 8607030108
Download: ML20211N466 (3)

Text

' Tc'=pho"' (* ") * ' ** ' o YANKEE ATOMIC ELECTRIC COMPANY TWX 710-380-7619

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1671 Worcester Road, Framingham, Massachusetts 01701 DCC 86-072 JE i,- 2.C2.1

' Yb) June 19, 1986

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FYR 86-056 United States Nuclear Regulatory Commission Washington, D.C. 20555 Attention: Eileen M. McKenna Project Manager, Project Directorate No. 1 Division of PWR Licensing-A

Reference:

(a) License No. DPR-3 (Docket No. 50-29)

Subject:

Electrical Loading at Yankee Nuclear Power Station (YNPS)

During Bus Cross-Tie Configurations Ms McKenna:

Yankee has recently completed electrical system studies at YNPS under various conditions. The analysis identified a concern in meeting the minimum starting voltage requirements for the HPSI pump motors when 480V busses No. 6-3 and No. 4-1 are cross-tied during heatup and cooldown operations, as shown in Attachment No. 1. This cross-tied configuration (limited to less than or l equal to 30 MWe) is normally used for only short periods of time (approximately 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />) when either coming off line or when coming back on line from a shutdown. The study also indicated that Station Service Transformer (SST)

No. 6 which feeds the two tied busses, could exceed its rated capability if a Safety Injection Actuation Signal (SIAS) occurs when the plant is in this configuration.

In order to resolve the above concerns, Yankee intends to install a new 1 2400V circuit breaker to connect SST No. 4 directly to 2400V bus No.1 as shown in Attachment No. 2. This modification will result in each 480 volt bus being fed directly from its own 2400V bus. This eliminates the need to tie the 480 volt busses together and thus alleviates the HPSI pump motor and transformer loading concerns. The new 2400 volt breaker will be installed during the next refueling outage, scheduled for May, 1987 In the interim, Yankee is statiorA.t t dedicated operator in the Control Room to trip specific plant br A n; a SIAS is received when the 480 volt busses are cross-tied. i'h x r .ons assure a normal plant response to a SIAS signal.

We trust that you will find this information satisfactory. If, however, you should desire additional information, please contact us.

Very truly yours, q

KANKEEATOMICELECTRICCOMPANY W Ai

. D. Haseltine L d

",I Project Manager 8607030108 860619 Yankee Project PDR ADOCK 05000029 P PDR

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