ML18219C125

Letter from Indiana & Michigan Power Co to NRC on Supplement to Abnormal Occurrence of Electrical Blackout Which Occurred on 2/17/1975

ML18219C125
Person / Time
Site:	Cook
Issue date:	04/18/1975
From:	Jurgensen R Indiana Michigan Power Co
To:	James Keppler NRC/RGN-III
References
LER 1975-005-00
Download: ML18219C125 (10)

Text

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XNCXDENZ REPORT FX

'ILE Indiana and Michigan DATE OF DOC DATE REC'D LTR TWX RPT OTHER ower Co- Bridgman, Mich. 49106 R.W. Jurgensen 4-18-75 4-23=75 TO: ORIG CC OTHER. SENT AEC PDR Mr. J.G. Keppler 1 signed E

1 SENT LOCAL PDR CLASS UNC LASS PROP INFO INPUT NO CYS REC'D DOCKET NO:

1 5o-315 Ltr supplementing AO 50-315/75- ENCLOSURES:

concerning the opening of 12AB and 12CD causin an electrical blackout" ~

ACKNOWLEDGEB

'DQ NQT REMOVE PLANT NAME. Donald C. Cook Nuclear Plant FOR ACTION/INFORMATION BUTLL=R (L) SCHWENCER (L) ZIEMANN (L) REGAN (E)

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< I ee meploell Qy ( INDIANA Er MICHIGANPDWEG CDMPANIY DONALD C. COOK NUCLEAR PLANT P.O. Box 458, Bridgman, Michigan 49106 e

~frfo OSHRo April 18, 1975 4'~

Mr. J. G. Keppler, Regional Office Of Inspection Director and Enforcement l CO ARRIC MMIGG fIfAfOR olf G II United States Nuclear Regulatory III Commi QP ~

Region 799 Roosevelt Road 5

Glen Ellyn, IL 60137 Operation License DPR-58 Docket No. 50-315 AO 50-315/75-5 Supplement

Dear Mr. Keppler:

On March 10, 1975, we reported an event which occurred at the Donald C. Cook'Nuclear Plant on February 17, 1975. The Abnormal Occurrence was an electrical blackout which occurred at 2332 hours0.027 days <br />0.648 hours <br />0.00386 weeks <br />8.87326e-4 months <br /> on February 17, 1975.

Plant conditions at the time of the event were:

a) Reactor was critical at approximately 6.5 percent power.

b) Feedwater supply was being shifted from the Auxiliary to the Hain Feed Pumps.

c) Preparations were being made for turbine-generator toll and startup.

d) Electrical system power supply was being received from the 345/765 KV tie transformer TR inI4 to the reserve transformers 101AB and 101CD to the 4 KV busses.

power from the 69/4 KV transformer

'mergency TR12EP was avail. able.

Emergency diesel generators AB and CD were available.

Description of Occurrence:

a) At 2332 hours0.027 days <br />0.648 hours <br />0.00386 weeks <br />8.87326e-4 months <br /> OCB 12AB and 12CD opened causing an electrical blackout.

b) Both Emergency Diesel Generators started and assumed their, assigned electrical load. There was 1200 KW on AB and 1800 KW on CD diesel generators. Emergency lights were, 4<( 78

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Mr. J Apri 1,of Page 2 eppler 1975 4

available throughout the plant. The reactor had tripped and was in a shutdown condition.

c) The dispatcher at Twin Branch was called to inform him of the loss of 'power and a switchman was requested to come to the plant to inspect the switchyards. The Plant Manager and Operations Supervisor were called and appraised of the conditions at the plant.

At approximately 2350 the Operating Engineer was sent to inspect the switchyards.,

February 18, 1975 e) At 0000 the Control Room Operator stripped the busses of all non-vital equipment.

At 0020 the D. C. powered oil pumps to the East and West Main Feed Pumps were secured.

g) At 0025 the Production Supervisor had the plant's electrical lighting load added to the Emergency Diesel Generators.

h) The Plant Manager and Operations Supervisor arrived at the site between 0030 and 0045.

The Production Supervisor and Shift Operating Engineer determined at this point that since the Emergency Diesel Generator was satisfactorily carrying the load, that seal water was being supplied to the Reactor Coolant Pumps, that boration by normal or emergency modes was available, they would not shift electrical to the Emergency Transformer TR12EP even though it was available. To have shifted electrical power to the- emergency transformer would require securing the diesel's and then energizing emergency power since interlocks prevent paralleling these two power sources.

At approximately 0030 the switchman arrived to assist the Operating Engineer with the inspection of the switchyards.

k) The turbine generator AC Bearing Oil Pump and Turning Gear were energized and the turbine generator was rolled 180 'degrees.

At 0143 the turbine generator and both main feed pumps were placed on the turning gear, the East Centrifugal Charging Pump was secured and .the Reciprocating Charging Pump was started.

At 0150 the plant air compressor was returned to service.

n) The inspection of the switchyards was completed. There were no Zone Isolation relay targets or HEA relay targets to

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Mr. J.~ ppler Apr,il Page 3

~oi' 1975, indicate 'a fault. The 345 KV bus 2 and 765 KV transformers were still energized and breakers OCB 12>'AB and 12 CD 'were open. The decision was made to remove the disconnect links between the generator and 81 Main Transformer. This would provide the capability to back feed'from the 345 KY bus 2 through the 0'1 Main Transformer through transformers TR1AB and TRlCD.

o) Since no electrical faults were indicated the decision was made by the'roduction Supervisor, Operating Engineer and Switchman to reclose OCB 12AB and 12CD. Breaker, 12CD was closed and approximately 20 seconds later breaker 12AB was closed., Immediately the 765 KV breaker and 345 KV bus 2 stripped. Investigation revealed an HEA target on breaker 12CD. A ground fault target was found on the 765 transformer zone protection relays.

p) At 0300 the generator disconnect links were removed.

q) At approximately 0400 the 765 KV breaker was closed re-energizing the 345/765 KV bus 2. Breakers 12AB and 12CD were open and tagged out for further investigation.

At 0410 the 345 KV breaker K was closed and the plant was supplied with electrical power from the 345 KV bus 2 through 0'1 Main Transformer to Transformers TRlAB and TR1CD to the 4 KV busses.

s) Between 0415 and 0430 the Emergency Diesel Generators were paralleled to the 4 KV off-site power and the electrical load was shifted to off-site power. The Emergency Diesel Generators were secured at 0439.

At 0508 number 2 Reactor Coolant Pump was started.

u) At 0525 all four Reactor Coolant Pumps were in operation.

The reactor coolant system pressure was 2000 PSIG and Tavg was 500oF.

v) At 0600 the Plant Heating Boiler,was returned to service.

x) The investigation of the electrical problem continued and

,,on, February 20, 1975, a defective splice on an underground found.'C cable between breaker '12AB and transformer TR101AB,was y) The defective splice was repaired on February-20, 1975, and normal electrical system lineup was 're-established at 0041 on February-21, 1975.

z) The reactor was taken critical at 0350 February 21,, 1975, and the power testing program was resumed.

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Mr.. J. jg April %P, eppl er 1975 pape 4 of 4 All underground cable splices between, breakers 12AB and 12CD were scheduled for inspection during a plant outage, scheduled for March 1975. There are a total of '16 underground cable splices.

The plant outage was started on March 18, 1975. All underground cable splices were inspected and/or tested and no additional defective splices were found. The electrical system is -in normal operation.

Desi nation of Cause of Occurrence The partial loss of off-site power'as the result of a defective splice in one 'cable between breaker 12AB and transformer TR101AB. The cause of the defective spl.ice was due to poor workmanship.

Anal sis of Occurrence There were no safety implications 'as a result of- this occurrence. At no time was the 'plant without a source of off-site electrical power..

The emergency back-up off-site- power supply, which is from a 69 KV line thru the 69/4 KV transformer TR12EP, was operable and would have been utilized in the event the diesel generators did not operate properly.

All'safeguards equipment performed as designed. There were no consequences or potential consequences from the standpoint of public health and safety.

Corrective Action The defective splice was repaired, the remainder of the underground splices were inspected and/or tested with no additional defective splices found.

Sincerely, R. W. Ju n Plant M age

/sy R. S. Hunter J. E. Dolan G. E.'ien R. J. Vollen K. R. Baker R. C. Callen Richard Walsh, Esq.

Peter Steketee, Esq.

PNSRC File

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