ML19332E839

Special Rept:On 891103,test Declared Valid Failure When Standby Diesel Generator 22 Attained Output Frequency of 58 Hertz.Caused by Oxidation of Relay 4EX3 in Governor Control Circuit.Contacts Cleaned & Burnished

ML19332E839
Person / Time
Site:	South Texas
Issue date:	12/04/1989
From:	Chewning R HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ST-HL-AE-3307, NUDOCS 8912130051
Download: ML19332E839 (4)

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WThe Light p;7v company P.O. Box 1700 liouston, Texas 77001 (713) 228 9211 Houston Lighting A: Power _.. :- - - - - - - - - - - -

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p December 4, 1989 ST-HL AE-3307 File No.: G02 l

U.-S. Nuclear Regulatory Commission Attention: Document Control' Desk

- Washington, DC 20555 South Texas Project Electric Generating Station Unit 2 Docket No. STN 50 499 Special Report Regarding A Diesel Generator Valid Failure On November 3. 1989 L

Pursuant to the South Texas Project Electric Generating Station

' Technical Specifications 4.8.1.1.3 and 6.9.2, Houston Lighting & Power submits the attached Special Report regarding a diesel generator valid failure which occurred on~ November 3, 1989.

If you should have any questions on this matter, please contact

.Mr. C. A. Ayala at (512) 972-8628.

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. W. Chewning Vice President Nuclear Operations

- RWC/BFR/n1

Attachment:

Special Report Regarding a Diesel Generator Valid Failure on November 3, 1989 y

8912130051 891204 '

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/P Regional Administrator,' Region IV Rufus S. Scott

/ Nuclear Regulatory Commission Associate General Counsel 611 Ryan Plaza Drive, suite 1000 Houston Lighting & Power Company Arlington, TX .76011 P. O. Box 1700 Houston, TX 77001 George Dick, Project Manager U.S. Nuclear Regulatory Commission INPO Washington, DC 20555. Records Center 1100 Circle 75 Parkway J. I..Tapia . Atlanta, CA ' 30339 3064 Senior Resident Inspector-c/o U. S. Nuclear Regulatory Dr. Joseph M. Hendrie Commission

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50 Be11 port Lane P. O. Box 910 Be11 port, NY 11713

-Bay City TX- 77414 D. K. Lacker J. R. Newman, Esquire Bureau of Radiation Control Newman & Holtzinger, P.C. Texas Department of Health 1615 L Street, N.W. 1100 West 49th Street Washington, DC 20036 Austin, TX 78704 R. L. Range /R. P. Verret Central Power & Light Company P; 0. Box 2121

-Corpus Christi, TX- 78403 J .C. Lanier Director of Generati'on.

City'of Austin Electric Utility 721 Barton Springs Road' Austin, TX 78704'

. R. J. ' Costello/M T. Hardt

. City'Public Service Board-

.P. O. Box 1771 San Antonio, TX 78296 Revised 11/15/89 L4/NRC/

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Attachment J

> ST-HL-AE-3307 Page 1 of 2 South Texas Project Electric Generating Station Unit 2 Docket No. STN 50 499 Special Report Regarding A Diesel Generator Valid Failure On November 3. 1989 Descrintion of Event:

On November 3, 1989 at 1231 hours0.0142 days <br />0.342 hours <br />0.00204 weeks <br />4.683955e-4 months <br />, Standby Diesel Generator (SDG) 22 was started to satisfy Technical Specification surveillance requirements. The generator attained an output frequency of 58 Hertz which was outside the acceptable range of 58.8 to 61.2 Hertz. The SDG was secured and the test was _

declared a valid failure.

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Troubleshootin6 was performed to determine the cause of the failure.

The problem was traced to oxidation of the contacts of relay 4EX3 in the governor control circuit. The relay places the governor in the isochronous  !

mode for independent operation of the SDG during an emergency. Small changes I in contact resistance can affect engine governor operation.

i on May 23, 1989, a non valid failure of Unit 1 SDG 13 occurred when l oxidation of a different set of contacts of a 4EX3 relay caused a loss of l engine speed control in the non emergency mode. As a result of that event, preventative maintenance activities were developed to clean and burnish the contacts on relay 4EX3 during the eighteen month SDG inspections. This activity has been completed on SDG's 11 and 13.

'Cause of Event:

i' The cause of this event was oxidized contacts on relay 4EX3.

Corrective Action:

The following corrective actions are being taken as a result of this event:

1. The contacts on relay 4EX3 on SDG 22 were cleaned and burnished on .

November 3, 1989. SDG 22 was successfully tested and returned to l service at 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br />.

2. In addition to the preventive maintenance activities already scheduled, the contacts on relay 4EX3 on SDG's 12, 21 and 23 will be cleaned and burnished during the next train outages which are currently scheduled to be completed by February 17, 1990. l

3. An evaluation will be performed of the 4EX3 relays to determine if a suitable replacement exists which is less prone to contact resistance changes. This evaluation will be completed by January 30, 1990.

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-Additional Information:

Per the criteria of Regulatory Guide 1,108, the failure described in . ,

this' report has been classified as a valid failure. This is the first valid failure of SDG 22; therefore, the test. interval-remains at 31-days. There

.J have been a total'of 18 valid tests of SDG 22 performed prior to this-failure- ,

.since' completion of the diesel generator reliability-demonstration, 1

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