B11335, Forwards Procedures Re Degraded Grid Voltage,Including Change 2,Rev 4 to OP2347B, Normal Station Svc Transformer 15G-2S & Change 2,Rev 5 to OP 2347A, Reserve Station Svc Transformer 15G-22S

Forwards Procedures Re Degraded Grid Voltage,Including Change 2,Rev 4 to OP2347B, Normal Station Svc Transformer 15G-2S & Change 2,Rev 5 to OP 2347A, Reserve Station Svc Transformer 15G-22S

ML20101D050
Person / Time
Site:	Millstone
Issue date:	12/04/1984
From:	Counsil W NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	John Miller Office of Nuclear Reactor Regulation
Shared Package
ML20101D053	List: B11335, Forwards Procedures Re Degraded Grid Voltage,Including Change 2,Rev 4 to OP2347B, Normal Station Svc Transformer 15G-2S & Change 2,Rev 5 to OP 2347A, Reserve Station Svc Transformer 15G-22S ML20101D056 ML20101D060 ML20101D065
References
B11335, TAC-51701, NUDOCS 8412210284
Download: ML20101D050 (5)

Text

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General Offices

• Selden Street, Berlin Connecticut p

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P.O. BOX 270 HART OR CONNECTICUT 06141-0270 December 4,1984 Docket No. 50-336 Bil335 Director of Nuclear Reactor Regulation Attn: Mr. James R. Miller, Chief Operating Reactors Branch #3 U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Gentlemen:

Millstone Nuclear Power Station, Unit No. 2 Degraded Grid Voltage As you requested, the procedures dealing with degraded grid voltage at Millstone Unit No. 2 are attached. Also attached is a brief explanation of how these procedures are used.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY k&'

W. G.' Counsil Senior Vice President 04122gg2g4 0 00 36 PDR A PDR P hDg

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e Docket No. 50-336 Attachment I Millstone Nuclear Power Station, Unit 2 December,1984

k Millstone Nuclear Power Station Unit No. 2 i

Degraded Grid Voltage

References:

- 1. - NNECO Operating Procedure OP2374B, Rev. 4, Changes 1 and. 2, Items 8.2(a) and 8.2(b), Normal Station Service Transformer 15G - 25

2. NNECO Operating Procedure OP2347B, Rev. 4, item 8.2, Normal Station Service Transformer 15G - 25.

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3. NNECO Operating Procedure OP2347A, Rev. 5, Item 8.2, Reserve Station Service Transformer 15G - 225.

4. NNECO Operating Procedure OP2384, Rev. 2, Engineered Safeguards Actuation.

As you requested, the procedures dealing with' supply of degraded grid voltages .

to the Millstone Unit No. 2 emergency buses are attached.

1.0 Degraded Voltage 90% (Level 2)

! .1.1 When the plant is in the normal mode, Reference #1 applies to the

!- Norrnal 5tation Service Transformer. A L 90% voltage operator action is required within a four (4) hour period.

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. 1.2 When the plant is in the normal mode, Reference #4 applies to the L

transformer 15G - 225. At 90% volta (Reserve Station Service Transformer)ge with a the timetransformer delay of 8+15G or 225, seconds is automatically tripped from the emergency buses and the loads are transferred to the diesel generators.

1.3 The time delay.in item 1.1 above allows for corrective action before L the equipment suffers loss of life. The time delay in Item 1.2 allows for the starting of large motors.

I - 2.0 Degraded Voltage 70% (Level 1/Undervoltage/ Loss of Normal Power) 2.1 The transformer 15G - 25 is automatically blocked from closing onto the 6.9 kV 25A&B and 4.16 KV 24A&B buses during a 70% voltage condition, Reference #2. This means that the transformer 15G - 25 is blocked from supplying the emergency buses.

2.1.1 When the plant ~ is in the normal or accident mode, Reference #4 applies to the transformer 15G - 25. At 70%

7 voltage the' transformer 15G - 25, with a time delay of L 0.5 seconds,'is automatically tripped from the emergency buses and the loads are transferred to the diesel generators.

2.2 The transformer 15G - 22S.is automatically blocked from receiving the in-house buses 24 C&D for an auto transfer during a 70% voltage g condition, Reference #3. This means that Item 2.1.1 above will:

automatically take over. .  %-

Also the transformer 15G - 22S is automatically blocked from closing onto the 6.9 kV buses 25A & B. This means that the transformer 15G

- 22S will not be supplying large non-emergency loads, Reference #3.

2.2.1 When L the plant is in-the normal or accident mode, Reference #4 applies to the transformer 15G - 225. At 70%

voltage the transformer 15G - 22S with a time delay of 0.5 seconds is automatically tripped from the emergency buses and the loads transferred to the diesel generators.

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. Docket No. 50-336 Attachment Il Millstone Nuclear Power Station, Unit 2 December,1984

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