ML19309B071

Discusses Commitment to Installation During Aug-Sept 1978 Refueling Outage of Second Level Voltage Protection Sys for Nuclear Svc Buses W/Coincident Logic Per NRC

ML19309B071
Person / Time
Site:	Rancho Seco
Issue date:	01/09/1978
From:	Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Reid R Office of Nuclear Reactor Regulation
References
TAC-10968, NUDOCS 8004020675
Download: ML19309B071 (3)

Text

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as.7ss NRC DISTRIBUTION Paa PART 50 DOCKET MATERIAL TO:

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DATEOFDOcUMENT Sacramento Municipal Util. Dist.

1/09/78 Mr. Robert W. Reid Sacramento, California DATE REcEiv' 2/78 1/1 J. J. Mattimoe OCgTTEn CNOTORIZED PROP INPUT PORM NUMBER OF COPIES RECEIVED PIO28GINAL

[NCLASSIFIE D l'CcOPy I 516 Al42O CESCRIPTION ENCLOSU RE Consists of info. rez second level voltage protection system for the nuclear service buses with coincident logic..w/att drawing.....

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DISTRIBUTION OF MATERIAL CONCERNING DIESEL ALARM CIRCUITRY FOR DIESEL GENERATORS PLANT NAME: Rancho Seco Unit No.1

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95813; (916) 452-3211 January 9,1978 Director of Nuclear Reactor Regulation

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Dear Mr. Reid:

In the District's letter of July 19, 1977, we committed to the installation, during the August - September 1978 refueling outage, of a second level voltage protection system for the nuclear service buses with coincident logic, as required by your letter of June 3,1977.

To satisfy this comitment, the circuit shown in Figure 1 (attached) is being proposed.

To insure that the District and the NRC have the same interpretation of our commitment, any recommendations or l

conn.ents on this circuit are requested.

Also, to insure installation of the equipment during the August - September 1978 refueling, your comments are required within 30 days of the date of this letter.

If we l

do not receive any coments from you within this time period, the District will assume you concur that the design meets your requirements.

A detailed explanation of the circuit is given below:

Three potential transformers will be used to monitor the bus voltage (refer to Figure 1).

Each potential transformer will monitor a different line-line voltage.

Connected to the secondary of each potential transformer will be an undervoltage relay, overvoltage relay, and a voltneter.

The contacts from the undervoltage and overvoltage relays are connected such that if either relay is removed, an alam will be rec 2ived in the control room on the plant annunciator and plant computer.

Nomally closed contacts from the overvolt-age and a normally opened contact frotn the undervoltage relay on the same PT are connected in series to operate an auxiliary relay (4AUL1, 4AUL2, and 4AUL3).

The auxiliary relays are de-energized for either an undervoltage or overvoltage condition.

The contacts N

i AN ELECTRIC SYSTEM S E RVIN G MORE THAN 600,000 IN THE HEART OF C A LIF0 R N I A

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R. W. Reid Jar.uary 9,1978 e

i from the auxiliary relays are arranged in two-out-of-I three logic.

This logic string is used to operate the bus unloading relay (4AULX). A contact from this relay is used to initiate bus unloading and diesel starting in the existing scheme.

The 628/TDE relay is a time delay on energizing relay that prevents an accidental bus unloading when the logic circuit is initially energized.

The 125V DC to Terminals 7 and 8 on the overvoltage and undervoltage relays is the control power for the relays.

All equipment used in this modification will be designed and installed to Class I seismic and quality assurance requirements.

The voltage and time delay settings for the second level protection circuit will be chosen to meet the criteria detailed in Position 1 of your letter of June 3,1977.

If you have any questions, please feel free to call.

Sincerely yours,

, %C S J. J. Mattimoe Assistant General Manager and Chief Engineer Attachment