ML20043B603

LER 90-007-00:on 900423,during Offsite Relay Testing,Oil Circuit Breaker Supplying Bus 3 Tripped Open,Resulting in Loss of Power to ESF Train B & Diesel Generator B Start. Caused by Deficient Procedure.Testing stopped.W/900523 Ltr

ML20043B603
Person / Time
Site:	Summer
Issue date:	05/23/1990
From:	Bradham O SOUTH CAROLINA ELECTRIC & GAS CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-007, LER-90-7, NUDOCS 9005300269
Download: ML20043B603 (4)

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10CFR50,73- , i South Carolina Electric & Gas Company - . OIP.) S. Bradham .t i P.O. Box 88 - Vici Pr:sident ~

fj t.. ** Jinkinsvills. Sc 20065-- Nudear Op3rctiona M e 1 -* ,i

(803) 3454040

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May-23, 1990 -!

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Document Control Desk '

.U. S. Nuclear Regulatory Commission

Washington, DC 20555-

SUBJECT:

Virgil C. Summer Nuclear Station r

Docket No. 50/395- -

Operating License No. NPF-12 a LER 90-007 Gentlemen:-

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-i Attached is Licensee Event Report No.90-007 for the Virgil C. Summer Nuclear  !

Station...This report is submitted pursuant to the. requirements of L10CFR50.73(a)(2)(iv).

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

i Very truly yours,. )

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0. S. Bradham se <* O i .4

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. Attachment l;

c: 0. W. Dixon, Jr./T. C. Nichols, Jr.

E. C. Roberts '

R. V. Tanner J. C. Snelson 4 S. D. Ebneter R. L. Prevatte I J. J. Hayes, Jr. J. B. Knotts, Jr. ~' !

General Managers INP0 Records Center

.C. A.-Price ANI Library G. J. Taylor Marsh & McLennan J. R. Proper NPCF (

R. B. Clary NSRC /

F. H. Zander RTS (ONO900049) l- T. L. Matlosz Files (818.05 & 818.07)

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~~) vts tu v sa. wen totcno sve nwon ca res D uo l l l AseTn ACT m,me . ,ao - 4. . . , an .u. ,-,, , nei On April 23, 1990, off-site personnel from the Systems Relaying Department informed-the Operations Department of the Virgil C. Summer Nuclear station (VCSNS) that they would be testing the-trip circuitry for the Oil Circuit Breakers-(0CBs) that isolate the 230 KV switchyard bus #2. The relays to be actuated during this test supply trip signals to both bus #2 and bus #3. The relay personnel were to disable the trip signals going to bus #3 such that the relay actuations would only trip the bus #2 OCBs. However, when the' relay was actuated, the OCBs supplying bus #3 tripped open resulting in loss of power to the "B" train ESF bus. This caused the "B". Diesel Generator (0/G) to start and load via the "B" ESF sequencer. Upon review of the status of the relays, it was discovered that the measures taken to disable the differential trip relay for ous #3 had not been effective. Thus, when the relay was tested the bus #3 0CBs sensed a differential trip signal and opened as required.

The D/G and usociati d loads were verified to be operating properly. The "A" train power sources remained operable throughout the event and all "B" train ESF equipment responded properly wi'.h power being supplied from the "B" D/G. There were no on-site failures of any equipnent and Technical Specifications were complied with at all times during this event.

. Systems Relaying Department is to provide " Lessons Learned" training to their personnel who may be involved in work in the switchyard, and detailed procedures will be developed to coordinate work activities in the switchyard with VCSNS scheduled activities.

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. LICENSEE EVENT REPOHT (LER) TEXT CONTINUATION Aa*aovio ous No moaio4 EXPIRES B0196 FACILITY NAME til DOCKET NUMBER 828 LER NUMBER 16e PAGE(3n uaa " St.Wa" "#J.D Virgil C. Summer Nuclear Station o ls lo lo lo l3 l9 l5 9l 0 -

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0l0 0l2 oF 0l3 TEXT (# more space as reeuwed, use erAmrerw/ NRC form .1ri6Cs/117 PLANT IDENTIFICATION:

Westinghouse - Pressurized Water Reactor EQUIPMENT IDENTIFICATION:

B Diesel Generator, XEG-001B EIIS - EK IDENTIFICATION OF EVENT:

An error made by off-site personnel while performing relay testing in the 230 KV switchyard (off-site source) resulted in the "B" train ESF bus experiencing a loss of power and, thus, caused the actuation of the "B" Diesel Generator (0/G).

EVENT DATE AND TIME:

April 13, 1990 at 1038 hours0.012 days <br />0.288 hours <br />0.00172 weeks <br />3.94959e-4 months <br />.

REPORT DATE:

May 23, 1990 This report was initiated by Off-Normal Occurrence Report 90-049.

CONDITIONS PRIOR TO : VENT:

The plant was in its fifth refueling outage with the reactor defueled.

Both "A" and "B" trains of on-site and off-site power sources were operable.

DESCRIPTION OF EVENT:

On April 23, 1990, off-site personnel from the Systems Relaying Department informed the Operations Department of the V hgil C. Summer Nuclear Station (VCSNS) that they would be testing the trip circuitry for the Oil Circuit Breakers (OCBs) that isolate the 230 KV switchyard bus #2. The relays to be actuated during this test supply trip signals to both bus #2 and bus #3. Bus #2 was de-energized, but bus #3 was energized and serving as the off-site source to the "B" train ESF bus. The relay personnel were to disable the trip signals going to bus #3 such that the relay actuations would only trip the bus #2 OCBs. However, when the relay was actuated, the OCBs supplying bus #3 tripped resulting in loss of power to the "B" train ESF bus. This caused the "B" D/G to start and load via the "B" ESF secuencer. The test personnel immediately recognized the loss of potential on bus

1. 3 and reclosed the OCB. Bus #3 was de-energized for approximately 10 seconds.

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DOCKET NUMBER W f LlR NUMBER (6) PAGE (3) vE*a "=.'.'  %*J:

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-CAUSE OF EVENT:

Upon review of the status of the relays, it was discovered that the measures taken to disable the differential trip relay for bus #3 had not been-effective. Thus,.

when.the relay was tested, the bus #3 OCBs sensed a differential trip signal and opened as required. The applicable procedure was followed but was generic and did not give detailed instructions for specific application with respect to the 230 KV switchyard at VCSNS. The procedure relied on the relay personnel to exercise the

-necessary controls.

ANALYSIS OF EVENT:

The D/G and associated loads were verified to be operating properly. The "A" train power sources remained operable throughout the event and all "B" train ESF equipment. responded properly with power being supplied from the "B" D/G. There were no on-site failures of any equipment and Technical Specifications were '

complied with at all times-during this event.

IMMEDIATE CORRECTIVE ACTION:

1. Off-site power was restored to XSW1DB.

2. Relay testing was stopped in the 230 KV switchyard.

3. "B" D/G was secured.

ADDITIONAL CORRECTIVE ACTION:

1. Systems Relaying Department is to provide " Lessons Learned" training to their personnel who may be involved in work in-the switchyard (to be completed by >

June 10, 1990).

2. ' Systems Relaying Department is to develop procedures to detail relay testing in the switchyard that would affect the in-plant system. Switchyard work will also be included into the VCSNS work schedule to ensure proper coordination of .

. activities. These procedures will be reviewed by VCSNS personnel prior to their approval (to be completed prior to RF-6).

PRIOR OCCURRENCES:

None.

NRC FORM 366A C 83)