ML17249A287

Responds to NRC Re Loss of Offsite Power. One Partial Loss & Two Complete Losses of Offsite Power Occurred Since Initial Operation.Three Partial or Complete Losses Occurred Before Plant Operation

ML17249A287
Person / Time
Site:	Ginna
Issue date:	11/15/1979
From:	White L ROCHESTER GAS & ELECTRIC CORP.
To:	Ziemann D Office of Nuclear Reactor Regulation
References
TASK-07-03, TASK-7-3, TASK-RR NUDOCS 7911230262
Download: ML17249A287 (14)

Text

RKGULATORY INFORMATION DISTRIBUTION SYSTEM (BIDS)

ACCESSION NBR: 7911?30262 DOC ~ DATEi 79/11/15 NOTAR D:

NO DOCKET FACIAL 50 244 Robert 'Emmet Ginna Nucl.ear Plantg Unit 1i Rochester G

05000244 AOTH ~ NAME AUTHOR AFFII.IATION NHITFiL~ Di Rocfiester Gas 8 Electric Corp.

RKC IP e'NAME RECIPIENT AFFILIATION Z IEMAFINr D ~ L ~

Operating Aeactoi s Branch 2

SUBJECT:

Responds to NRC 790925 ltr re loss of o,ffsite power events, One partial loss of offfsite power 8

two complete losses of offsite powei events since initial operation,'three partial or complete loss of-power events before p'lant operation, DISTRIBUTION CODEX'015S COPIES RECEIVED ~ LTR ENCl SIZE:

TITl.E: Onsite Emergency Power Systems gpTps..C.

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ROCHESTER GAS AND ELECTRIC CORPORATION o

89 EAST AVENUE, ROCHESTER, N.Y. 14649 LEON D. WHITE, JR.

VICE PRESIDENT TELEPHONE AREA COOS 7IS 546.2700 November 15, 1979 Director of Nuclear Regulation Attention:

Mr. Dennis L. Ziemann, Chief Operating Reactors Branch 52 Division of Operating Reactors U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

Loss of Offsite Power Events at the R.E.

Ginna Nuclear Power Plant Docket No. 50-244

Dear Mr. Ziemann:

In an effort to respond to your reguest for additional information concerning the loss of offsite power at Ginna Station, a detailed review of all such events was undertaken.

Each event is summarized below using the format shown on the Enclosure to your September 25, 1979 letter.

Event 1:

to the vsusso ~6, There has been one event since initial plant operation in which a partial loss of offsite power occurred.

This is summarized under Category A.

There have been two events since initial plant operation in which a complete loss of offsite power 'occurred.

These are summarized under Category B.

There were three partial or complete losses of offsite power which occurred prior to plant operation.

These are summarized under Category C.

Category A:

Losses of offsite power where less than all offsite power was lost.

Attachment I is a single line diagram of the offsite power system as well as the in-plant bus arrangements for Ginna Station.

From this diagram it can be seen that the primary offsite source is circuit 767 which is supplied by the 115 kV grid through number 6 transformer.

On January 2,

1971, a bushing failure on number 6 transformer occurred taking it and conseguently 767 circuit out of service.

When this occurred the two onsite diesel generators automatically started.

The safeguard

loads, however, were manually placed on backup offsite source, 751 circuit.

ROCHESTER GAS AND ELECTRIC CORP.

~DATE November 15, 1979 To Mr. Dennis L. Ziemann, Chief SHEET NO.

Question: l.

How many circuits to the offsite network are normally available and how many were lost during the event?

Response

The primary offsite source, 767 circuit, was lost during this event but, the backup source, circuit 751, was manually placed into service.

Question:

2.

What was the cause of the event?

Response

A bushing failure on number 6 transformer.

Question:

3.

Why did the other lines not fail when some did fail?

Response

Circuit 751 emanating from Station 204 remained energized during this event because the two 115 kV lines, circuits 908 and 911, the two sources for 751 circuit, remained in service.

Question:

4.

Was any voltage increase or decrease experienced just prior to or during the outage?

If so, please give details, voltages

reached, affects, etc.

Response

There was no recorded increase or decrease in system voltage prior to the outage.

There was only an abrupt loss of voltage during the event which lasted until the backup sources was manually placed into service.

Question:

5.

Was any frequency decay experienced just, prior to or during the outage?

If so, please give details, lowest frequency reached, decay rate, affects on equipment operation, etc.

Response

There were no recorded changes in system frequency prior to or after the outage.

Question:

6.

How long was power unavailable from the circuit?

Response

Circuit 767 was out of service for approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

Question:

7.

Date of Event..

Response

January 2, 1971.

==

Conclusion:==

This bushing failure was a random occurrence.

Spare parts are maintained so that future outage times will remain at 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> or less.

ROCHESTER GAS AND ELECTRIC C RP.

DATE November 15, 1979 To Mr. Dennis L. Ziemann, Chief SHEET NO.

Category B:

Losses of all offsite power.

Event. 1:

Four 115 kV transmission lines, circuit numbers

908, 911, 912 and 913 are used to distribute the net output of Ginna Station (435 MWe).

On the day of the event, October 21, 1973, circuit 912 was taken out of service for substation maintenance.

Con-sequently the remaining three 115 kV circuits (908, 911 and 913) began carrying an increased load.

This higher loading caused the lines of 908 circuit to sag.

It was determined that "B" phase of 908 sagged and flashed over onto the underbuilt 702 circuit.

Circuit 702 is a 34.5 kV line located just south of Station 204.

The flashover appeared as a fault on both lines and both lines cleared (opened).

With both 908 and 912 circuits out. of

service, 911 and 913 circuits experienced a 230 MWe power swing.

This power swing appeared as a fault to the relays on 911 and 913 circuit and the lines tripped out of service 65 cycles after the flashover.

With all four transmission lines opened, both a turbine and a reactor trip followed.

Since Station 204 is supplied by circuits 908 and 911, when they tripped the source for circuit 751 was lost.

The remaining events were as reported in our October 31, 1973 letter from Keith W. Amish, RG&E to John F.

O'eary, AEC.

Question:

1.

How long was the power off?

How long for partial recovery?

Please give details.

Response

The two offsite sources and the time each were out of service are taken from the Daily Operating Record for 10/21/73.

The LOAD DISPATCHER'S DAILY OPERATION RECORD Attachment II, indicated that 908 circuit was first to be put. back into service.

Switch 90822 at Station 121 closed at 0632 hours0.00731 days <br />0.176 hours <br />0.00104 weeks <br />2.40476e-4 months <br /> energizing Station 204 and 751 circuit.

Switch 90812 at 13A was closed at 0709 hours0.00821 days <br />0.197 hours <br />0.00117 weeks <br />2.697745e-4 months <br />, thus energizing Station 13A and 767 circuit.

The outage times are:

d 751 767 0552 0552 0632 40 min.

0709 1 hr.

17 min.

Question:

2.

If turbine trip occurred, howd soon after did loss of offsite power occur?

Response

The loss of all outgoing 115 kV transmission lines from Station 13A caused the generator breakers to trip which resulted in an immediate turbine and reactor trip.

0 l

I ROCHESTER OAS AND ELECTRIC C RP.

DATE November 15, 1979 To Mr. Dennis L. Ziemann, Chief SHEET NO.

Question:

3.

If power was recovered promptly (10 minutes or less),

was it due to automatic or manual actions?

Response

Offsite Power was partially recovered in 40 minutes due to manual action.

Question:

4.

Was any voltage increase or decrease experienced just prior to or during the outage?

If so, please give details, voltages

reached, affects, etc.

Response

There were no abnormal voltage conditions prior to the outage.

During the outage there was an abrupt loss of voltage at Stations 13A and 204.

This resulted in the loss of all offsite power coincident with the turbine/

reactor trip.

Question:

5.

Was any frequency decay experienced just prior to or during the outage?

If so, please give details, lowest frequency reached, decay rate, affects on equipment operation, etc.

Response

There was no recorded change in system frequency prior to the event,

however, during the event there was an excursion to 59.76 Hz as shown in the attachment III.

Question:

6.

Date of Event.

Response

October 21, 1973 Since this outage, the relaying on the four 115 kV lines has been upgraded.

This upgrading plus the implementation of emergency procedure E-4, Station Blackout Operation, as described in the October 31, 1973 letter, greatly reduces the possiblity of this event reoccuring in the future.

Event 2:

Question:

1.

The overhead 34.5 kV bus at Ginna Station is powered by either the primary 34.5 kV circuit,

source, 767 circuit, or the backup 34.5 kV source, 751 circuit.

On March 4, 1971, while the plant was at cold shutdown, a section of the plant siding (facade) fell onto the 34.5 kV open bus section causing the loss of all offsite power.

How long was the power off?

How long for partial recovery?

Please give details.

Response

Both offsite sources were available after the bus fault was cleared, approximately 30 minutes after the loss of all offsite power.

ROCHESTER GAS AND ELECTRIC CORP.

DATE November 15, 1979 To Mr. Dennis L. Ziemann, Chief SHEET NO.

Question:

2.

If turbine trip occurred, how soon after did loss of offsite 'power occur'?

Response

No turbine trip occurred because the plant was already at. cold shutdown.

Question:

3.

If power was recovered promptly (10 minutes or less),

was it due to automatic or manual actions'?

Response

Offsite Power was recovered due to manual action.

Question:

4.

Was any voltage increase or decrease experienced just prior to or during the outage?

If so, please give details, voltages

reached, affects, etc.

Response

There was no increase or decrease in voltage just prior to the outage.

An abrupt. loss of voltage to all safety and non-safety related loads occurred during the event.

Question:

5.

Was any frequency decay experienced just prior to or during the outage?

If so, please give details, lowest frequency reached, decay rate, affects on equipment operation, etc.

Response

No frequency decay was recorded prior to the loss of all offsite power.

Question:

6.

Date of Event.

Response

March 4, 1971.

==

Conclusion:==

Category C:

After this event, it was discovered that the wrong clips were used to attach the siding.

The proper clips were installed and the likelihood of this event reoccurring is reduced.

All other losses of offsite power occurred prior to 12/2/69, date of initial plant operation, and are listed below:

Date of Event Cause Circuit 4 Lost/

Duration 12/5/68 Sheet of metal faulted 767 8 751/unknown the 34.5 kV bus.

5/17/69 unknown 767/unknown 5/19/69 Panel Trip 767/unknown Since these events occurred prior to initial plant operation little data was retained and more specific details of these events are unavailable.

ROCHESTER GAS AND ELECTRIC CORP.

DATE November 15, 1979 To Mr. Dennis L. Ziemann, Chief SHEET NO.

If there are any questions concerning this response, please contact us.

Very truly yours,

~p L. D. White, Jr.

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