ML20024D698

LER 83-074/03L-0:on 830603,during Emergency Diesel Generator a Operability Surveillance Test,Normal 115 Kv Power Supply to Vital Bus Lost & Diesel Generator Output Breaker Tripped Open.Caused by Electrical surge.W/830729 Ltr

ML20024D698
Person / Time
Site:	Summer
Issue date:	07/29/1983
From:	Dixon O, Fields H SOUTH CAROLINA ELECTRIC & GAS CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
LER-83-074-03L, LER-83-74-3L, NUDOCS 8308080001
Download: ML20024D698 (4)

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EVENT DESCRIPTION AND PROBASLE CONSEQUENCES 01o l o l2 l l With the Plant in Mode 1, the "A" Emergency Diesel Generator ms connected to l j o l3 ; l Vital Bus 1DA and loaded to 4250kw during its operability surveillance test. 'Ibe ;

j o l4 l l normal ll5kv power supply to the vital bus was lost and the diesel generator out- l l o l s l l Put breaker tripped open. 'Ihe diesel was shut down and locked out by a phase l j o j e l l differential relay, thereby losing all A.c. power input to the vital bas. No j

gg,;gadverse consequences resulted as the redundant vital bus remained operable for j loI8[lP l ant safeguards.

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LE_J@l F l@ lZl@ lZl@ l 0 l 0l 010 l lYl@ l N@ l a@ l 21 919l 9l SS 3. SS 3. 3, .. ., 4 .3 .. .7 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h I 110 l l The event was caused by an electrical surge fem a lightnirn storm. 'Ihe same l l1l1IItrinned: 1) The normal oower feed breaker for Vital Bus 1DA ooen on over- l l 1 l 2 l l current. 2) Tha di esel generator output brenker onen on overcurrent and chase l l 113 l l differential. 'Ihe licensee will evaluate additional surge suppression circuitry l l 114 l l to protect the diesel generator circuitry. l 1 . . . a

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NUCL Am Open4TicNS July 29, 1983 f2 Mr. James P. O'Reilly Regional Administrator U.S. Nuclear Regulatory Commission Region II, Suite 2900 101 Marietta Street, N.W.

Atlanta, Georgia 30303

SUBJECT:

Virgil C. Summer Nuclear Station Docket No. 50/395 Operating License No. NPF-12 Thirty Day Written Report LER 83-074

Dear Mr. O'Reilly:

Please find attached Licensee Event Report #83-074 for Virgil C.

Summer Nuclear Station. This Thirty Day Report is required by Technical Specification 6.9.1.13.(b) as a result of entry into Action Statement (b) of Technical Specification 3.8.1.1,

" Electrical Power Systems, A.C. Sources," and Action Statement (a) of Technical Specification 3.8.3.1, " Electrical Power Systems, Onsite Power Distribution," on July 3, 1983.

Should there be any questions, please call us at your convenience.

Very truly yours, O. W. D xon, Jr.

HCF:OWD/mac/fjc Attachment cc: V. C. Summer C. L. Ligon (NSRC)

E. H. Crews, Jr. G. J. Braddick T. C. Nichols, Jr.,/O. W. Dixon, Jr. J. C. Miller E. C. Roberts J. L. Skolds J. B. Knotts, Jr.

H. N. Cyrus Group / General Managers I&E (Washington)

O. S. Bradhan Document Management R. B. Clary Branch C. A. Price INPO Records Center A. R. Koon NPCF File (Lic./Eng.)

D. A. Lavigne g;pClSLC' f6" d M J

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b S Mr. James P. O'Reilly LER No.83-074 Page Two July 29, 1983 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES At 2315 hours0.0268 days <br />0.643 hours <br />0.00383 weeks <br />8.808575e-4 months <br /> on July 3, 1983, the Plant was operating in Mode 1.

The "A" Emergency Diesel Generator (XEG001A) was connected to Engineered Safety Feature (ESP) Bus lDA and was loaded to 4250kw for the performance of an operability surveillance test. A lightning storm caused an electrical surge on the ll5kv offsite power source for ESF Bus lDA which tripped OCB 1802 (located at the source of the ll5kv line) open on overcurrent. Si multa-neously, the power surge caused the XEG001A output breaker to trip open on both "overcurrent" (51VDG relay) and " phase differential" (87DGA relay). This de-energized ESF Bus lDA and shutdown the diesel due to the actuation of the phase differential relay.

The Engineered Safety Features Load Sequencer (ESFLS) actuated in response to the dead bus and sequenced through Output #7, which opened both the Normal and Alternate offsite power supply breakers for ESF Bus lDA. At this step, the ESFLS stopped sequencing because XEG001A was shutdown and locked out by the phase differential trip. OCB 1802 automatically reclosed and re-energized the ll5kV line. However, the ESFLS had locked out the Normal and Alternate Power Supply Breakers and prevented their reclosure from the Main Control Board. ESF Bus lDA remained de-energized until 0025 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br />, July 4, 1983, for a total time of one hour and ten minutes. By this time, all lockouts had been reset and the Normal offsite power supply breaker was closed to energize ESF Bus lDA.

During the period that ESF Bus 1DA was inoperable, all Train "B" ESF systems remained operable and the minimum number of systems required for safe plant shutdown, as evaluated in the Accident Analysis, was satisfied. No adverse consequences to the safety of the public or the plant resulted from this event.

CORRECTIVE ACTION Due to the loss of ESF Bus lDA, Technical Specification 3.8.3.1, Action Statement (a), was applied. Power was restored prior to the fourteen (14) hour time limit for proceding to cold shutdown.

Technical Specification 3.8.1.1, Action Statement (b), was also applied. An electrical alignment verification for the "B" train ESF had just been completed at 2200 hours0.0255 days <br />0.611 hours <br />0.00364 weeks <br />8.371e-4 months <br /> on July 3,1983. The "B" Diesel Generator Operability Test had been completed at 2232 hours0.0258 days <br />0.62 hours <br />0.00369 weeks <br />8.49276e-4 months <br />, July 3, 1983.

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Mr. Janes P. O'Reilly LER No.83-074 Page Three July 29, 1983 CORRECTIVE ACTION - Continued Component Cooling Water Train A (powered by lDA) was supplying Reactor Coolant Pump cooling water. Component Cooling Water Train B was started and cooling water was restored to the Reactor Coolant Pump in less than ten (10) minutes.

Defective parts in XEG-001A were repaired and the equipment was declared operable at 0820 hours0.00949 days <br />0.228 hours <br />0.00136 weeks <br />3.1201e-4 months <br />, July 5,1983, af ter the satisfactory performance of the applicable surveillance procedure.

The Licensee plans to evaluate the need for developing additional surge suppression circuitry to protect the emergency diesel generator circuitry from lightning induced surges. This evaluation will be completed by October 31, 1983. Any resulting modifications will be implemented upon design approval and material procurement.

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