ST-HL-AE-4713, Special Rept on:940203,standby Diesel Generator 11 Failed to Obtain Normal Voltage & Frequency.Caused by Relay Contact Failure.Investigation of Event Still Ongoing.Results of Investigation Will Be Documented in Special Rept

Special Rept on:940203,standby Diesel Generator 11 Failed to Obtain Normal Voltage & Frequency.Caused by Relay Contact Failure.Investigation of Event Still Ongoing.Results of Investigation Will Be Documented in Special Rept

ML20064F797
Person / Time
Site:	South Texas
Issue date:	03/07/1994
From:	Cloniger T HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ST-HL-AE-4713, NUDOCS 9403150443
Download: ML20064F797 (4)

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March 07 ,1994 ST-lil AE-4713 File No.: G02 10CFR50 i U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 l South Texas Project  ;

Unit 1 Docket No. STN 50-498 l Special Report Regarding l Standby Diesel Generator #11 Valid Failure l

Pursuant to the South Texas Project Electric Generating Station (STPEGS) Technical Specifications 4.8.1.1.3 and 6.9.2,11ouston Lighting & Power submits th attached Special Report regarding a Standby Diesel Generator (SDG) #11 valid failure which occurred on February 3,1994. l If you should have any questions on this matter, please contact Mr. S.M. IIcad at  ;

(512) 972-7136 or myself at (512) 972-8787.

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Special Report Regarding Standby Diesel Generator #11 Valid Failun-1d0060 s _m-,

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Ilouston Lighting & Power Company South.rexas Project Electric Generating Station ST-IIL- AE-4713 File No: G02 '

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Regional Administrator, Region IV G.E. Vaughn/f.M. Puckett U.S. Nuclear Regulatory Cothmission Central Power and Light Company 611 Ryan Plaza Drive, Suite 400 P.O. Box 2121 -

Arlington, TX 76011 Corpus Christi, TX 78403 Lawrence E. Kokajko Project Manager Rufus S. Scott U.S. Nuclear Regulatory Commb,3 ion Associate General Counsel Washington, DC 20555 121115 Houston Lighting & Power Company P.O. Box 61867 David P. Loveless Houston, TX 77208 Senior Resident inspector c/o U.S. Nuclear Regulatory Commission INPO P.O. Box 910 Records Center Bay City, TX 77414 700 Galleria Parkway Atlanta, GA 30339-5957 J.R. Newman, Esquire Newman & Holtzinger, P.C., STE 100 Dr. Joseph M. Hendrie 1615 L Street, N.W. 50 Bellport Lane Washington, DC 20036 Bellport, NY l1713 K.J. Fiedler/M.T. Ilardt D.K. Lacker City Public Service Board Bureau of Radiation Control P.O. Box 1771 Texas Department of Health San Antonio, Tx 78296 1100 West 49th Street Austin, TX 78756-3189 J.C. Lanier/M.B. Lee City of Austin Electric Utility Departnent 721 Barton Springs Road Austin, TX 78767 r

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Unit 1 Docket No. STN 50-498 Special Report Regarding Standby Diesel Generator #11 Valid Failure DESCRWTION OF EVENT On February 3,1994 at 0204 hours0.00236 days <br />0.0567 hours <br />3.373016e-4 weeks <br />7.7622e-5 months <br />, Unit I was in Mode 4, while perforrning surveillance test OPSP03-DG-0001, " Standby Diesel Generator 11(21) Operability Test". Standby Diesel Generator 1I (SDG 11) failed to obtain normal voltage and frequency during an emergency-mode start. The engine came up to rated speed, however, there was no indication of generator voltage output in the control room or locally. The engine was subsequently secured. The diesel start was classified as a valid failure, and Standby L)iesel Generator 11 was declared inoperable.

Static troubleshooting checks were performed on the voltage regulator and exciter Held Cash circuits. The troubleshooting efforts identiDed faulty contacts on the VR1 (voltage release) relay that supply power to the field flash relay, The normally-closed contacts were found intermittently open, discolored, and badly pitted.

All other inspected components of the voltage regulator and exciter field flash circuits were found satisfactory. The VRI, VR2,14FFXI, and 14FFX2 relays were replaced. On completion of the specified maintenance, the diesel generator was test started, both in the test mode, and in the emergency mode, in both starts, Standby Diesel Generator. ll operated as designed, coming up to speed and voltage well within the required 10 seconds. No anomalies were noted in the operation of the Geld Dash circuit, or the voltage regulator. A satisfactory 4%

hour surveillance test was subsequently performed. Standby Diesel Generator 11 was placed on increased surveillance frequency with three additional surveillances conducted satisfactorily, llowever, on March 1,1994, during a subsequent performance of an increased frequency surveillance Standby Diesel Generator 11, again failed to attain voltage and frequency.

Additional investigations are now in progress.

CAUSE OF EVENT The cause of this event was initially believed to be simple relay contact failure of the -

VR1 and VR2 relays (Potter Brumfield model KUP14D15110vde). Because of the March I, .

1994 event, this cause is being further reevaluated. The cause of both events will be provided in the Special Report for the March 1,1994 event. i m e mom.a

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a IIouston I.ighting & Power Company Soutl* Texas Project Electric Generating Station Attachment ST-IIL-AE-4713 Page: 2 of 2 ANALYSIS OF EVENT The problem reported during testing of the 14FFX1 and 14FFX2 relays was determined  !

to be caused by the setup used during the initial field testing. The relays were first connected to the test power supply and meters by temporary leads using end-clips which can give poor connections and inaccurate results. Later testing of the subject relays, while installed in a test base with power supply and testing leads securely fastened, proved the' relays were indeed operating as designed, with no indications of failure. Further satisfactory test results from a .

sample of other like relays further confirmed that the initial test indications were misleading.

An analysis of both events will be provided in the Special Report to be submitted for the March 1,1994 event.

CORRECTIVE ACTIONS

1. Due to an apparently similar failure for Standby Diesel Generator 11 on March 1,1994, the investigation of this event is ongoing. Results of the investigation will be documented in the Special Report which will be submitted for the March 1,1994 event. Corrective actions will be provided for both events.

ADDITIONAL INFORMATION The failed component is VR1, a Potter Brumfield model number KUP-14D15110vde 3-pole double-throw relay.

At the time of this event, there was one valid failure in the past twenty (20) valid tests and four valid failures in the last one hundred (100) tests for Standby Diesel Generator #11. Due to the exceedance of both trigger values, the testing frequency has been accelerated to weekly.

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