ST-HL-AE-3532, Special Rept:On 900711,nonvalid Failure of Standby Diesel Generator 13 Occurred.Caused by Loose Connections on Terminal Points on Test Mode Trip Circuitry.Connections Tightened

Special Rept:On 900711,nonvalid Failure of Standby Diesel Generator 13 Occurred.Caused by Loose Connections on Terminal Points on Test Mode Trip Circuitry.Connections Tightened

ML20058P323
Person / Time
Site:	South Texas
Issue date:	08/10/1990
From:	Kinsey W HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ST-HL-AE-3532, NUDOCS 9008160204
Download: ML20058P323 (4)

Text

., _ .__ _ . . . __.

o The Light -

c o mp a nySouth Texas Project Electric Generating P. O. Station Box 289 Wadsworth, Texas 77483

. Houston 1,lghting & Power August 10s 1990 ST HL AE 3532 File No.: G02 '

10CFR50.36(c)(5)

U. S. Nuclear RegLlatory Commis. ion Attention: Document Control Desk Washington, DC 20555 South Texas Project Electric Generating Station Unit 1 Docket No. STN 50 498 -

Special Report Regarding A Nonvalid Failure of #13 Standby Diesel Generator on July 11. 1990 Pursuant to the South Texas Project Electric Generating Station Company Technical Specifications 4.8.1.1.3 and 6.9.2, Houston Lighting & Power (HiAP) submits the attached Special Report regarding a diesel generator nonvalid failure which occurred on July 11, 1990.

If you should have any questions on this matter, please contact Mr. F- M. Head at (512) 972-7136 or myself at (512) 972 7800.

Warren H. Kinsey, J  !

Vice President 1 l

Nuclear Generation SMH/n1 l

Attachment:

Special Report Regarding i A Nonvalid Failure of #13 Standby Diesel Generator on July 11, 1990 l

9008160204 900010 PDR ADOCK 05000498 g PNV 1

l C 001..0 >

A1/SPR-SDG2.S01 A Subsidiary of Houston Industries incorporated

August 10, 1990 Houston Lighting & Power Compan' ST HL AE 3532 South Texas Project Electric Generating Station File No.: C26 Page 2 F

r ec: ,

Regional Administrator. Region IV Rufus S. Scott Nuclear Regulatory Commission Associate General Counsel 611 Ryra Plaza Drive, Suite 1000 Houston Lighting & Power Company Arlington, TX 76011 P. O. Box 61867 Houston, TX 77208 Cearge 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 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 D. E. Ward /R. P. Verret Central Power & Light Company P. O. Box 2121 Corpus Christi, TX 78403 J. C. Lanier '

Director of Generation 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 12/15/89 ,

l' L4/NRC/

l s .  !

i

.. i i

Attachment i ST-HL-AE-3532 l

• • Page 1 of 2 ,

i

?

South Texas Project Electric' GenJrating Station  ;

Unit 1 i Docket No. STN 50 498 i

. Special Report [

Regarding A Nonvalid Failure of #13 i Standbv Diesel Generstor on July 11. 1990. ,

i DESCRIPTION OF EVENT: l On July 11, 1990 Unit 1 was.in Mode 1 at 100 percent power. At >

approximately 1334 hours0.0154 days <br />0.371 hours <br />0.00221 weeks <br />5.07587e-4 months <br />, #13 Standby Diesel Generator-(SDG) was started in ,

the emergency mode for a surveillance test. After release from the emerge'acy ,

mode, the diesel ran for 36 minutes at which time it tripped. No remote or

! local alarms were received except for,a green light on the local panel which-

• indicated a tripped condition. This trip was categorized as a Nonvalid l failure and is similar to three other nonvalid failures reported previously to >

the NRG on July 12, 1990 (ST-HL AE 3504). -

As in the previous trips, investigation centered on the 86S relay, which deenergizes when a non emergency trip occurs. The 86S relay was inspected and t a terminal conraction found to be loose was tightened. At 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br />, a surveillance test was conducted and completed satisfactorily. However, during  :

the cooldown cycle the diesel again tripped with symptoms similar to those of '

previous trips. Troubleshooting, which included two additional starts of the ,

SDG, continued with no conclusive results. Since the SDG had successfully completed the surveillance test, it was declared operable.

On August 1, during additional troubleshooting, two terminal lugs found loose were tightened. Contacts for eight test mode trip relays are in the circuit between these two points. It was postulated that these loose connections could have caused the unexplained trips encountered by SDG #13.

Three additional testa were run on SDG #13 following identification of the loose connections with each being successfully completed. These tests support the conclusion that the loose _ connections were the cause of the spurious trips on SDG #13.

i CAUSE OF EVENT:

The trip of SDG #13 on July 11, 1990 as well as trips that occurred June 12 and 13, are believed to have been caused by-loose connections c.

terminal points in the test mode trip circuitry.

t A1/SPR SDG2.S01 9

e~,

t

, - p.

. l Attachment  !

ST HL AE 3532

Page 2 of 2

• i ANALYSIS OF EVENT:  :

l The first start on July 11 is classified as a ncnvalid failure since the loose connections are located in the test mode trip circuitry and as such

~

l could not prevent SDC #13 for starting or loading in the emergency mode. The second start is considered a-valid test while the third and fourth starts are  ;

considered non tests since the SDG was started for troubleshooting purposes.

l 1.

CORRECTIVE ACTION:

The loose connections which are believed to have been responsible for the SDG #13 failure have been tightened. HL&P will investigate whether  ;

thermography can be successfully used on SDG control circuitry to detect loose leads. If the results of.this investigation prove positive, thermography will be incorporated into the SDG preventive maintenance program. The investigation will be completed by September 7,' 1990.

ADDITIONAL INFORMATION:

As indicated above, the three nonvalid failures of SDG #13 that occurred I

on June 12 and 13,1990 are believed to have also been caused by the loose connections in the test mode trip circuitry. ,

t Per STPEGS Technical Specification 3.8.1.1, there have been no valid failures in the last 20 valid tests of SDG #13 and the number of ve'.id '

failures in the last 100 valid tests is less than-four (4), therefore, the testing frequency for SDG #13 remains at once per 31-days.

1 1

i i

B i

A1/SPR-SDG2.S01

.-