ML20029C122

LER 91-004-00:on 910215,loss of Offsite Power Actuation Occurred During Routine Maint.Caused by Lack of Attention to Work Performance Methods.Training Conducted for Maintenance personnel.W/910315 Ltr

ML20029C122
Person / Time
Site:	South Texas
Issue date:	03/15/1991
From:	Ayala C, Harrison A HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-91-004, LER-91-4, ST-HL-AE-3174, NUDOCS 9103260059
Download: ML20029C122 (5)

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. The Light company I'n llox 1700 Ilouston, 'liu 77001 (713) 228 9211 llouston 1.lghting k I'uwer March 15, 1991 ST llL.AE 3714 File No.: C26 10CFR50.73 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Vashington, DC 20555 South Texas Project Electric Cenerating Station Unit 1 Docket No. STN 50 498 Licencee Event Report 91 004 Regarding a Partial Loss of Offsite Power Actuation Durin Q outine Mainte. Hat.lGI Pursuant to 10CFR50.73, llouston Lighting & Power (Ill4P) submits the attached Licensee Event Report 91 004 regarding a partial loss of offsite power actuation during routine maintenance. This event did not have any adverse impact on the health and safety of the public.

If you should have any questions on this matter, please contact Mr. C. A. Ayala at (512) 972 8628.

([7 4tekh-m sAv . liarrison Manager Nucicar Licensing RAD /sgs Attrehment: LER 91 004 (Unit 1) 1 I LER\91063001.U1 A Subsidiary of Iloustrtl Industrich lOtorporated /

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Regional Administrator, Region IV Rufus S. Scott Nuclear Regulatory Commission Associate General Counsel 611 Ryan Plaza Drive, Suite 1000 llouston Lighting 6 Power Company Arlington, TX 76011 P. O. Box 61867 llouston, TX 77208 Ceorge Dick, Project Manager U.S. Nuclear Regulatory Commission INPO Washington, DC 20555 Records Centor 1100 Circle 75 Parkway J. I. Tapia Atlanta, CA 30339 3064 Senior Resident Inspector c/o U. S. Nuclear Regulatory Dr. Joseph M. llendric Commission 50 Bellport Lane P. O. Box 910 Be11 port, NY 11713 Bay City, TX 77414 D. K. Lacher J. R. Newman, Esquire Bureau of Radiation Control Newman 6 iloitzinger, P.C. Texas Department of llealth 1615 L Street, N.W. 1100 West 49th Street Washington, DC 20036 Austin, TX "

5 3189 D. E. Ward /T. M. Puckett Central Power and Light Company P. O. Box 2121 Corpus Christi, TX 78403 J. C. Lanier/M. B. Lee City of Austin Electric Utility Department P.O. Box 1088 Austin, TX 78767 R. J. Costello/M. T. Hardt City Public Service Board P. O. Box 1771 San Antonio, TX 78296 Revised 01/29/91 L4/NRC/

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Te l 1 l On February 15, 1991, Unit 1 was in its third refueling outage with no fuel in the reactor vessel. At 0259 hours0.003 days <br />0.0719 hours <br />4.282407e-4 weeks <br />9.85495e-5 months <br />, a partial loss of offsite power occurred during maintenance of an overcurrent-protection relay, The supply breaker to 13.8 kV4tandby bus lit tripped which supplies power to the 4.16 kV Engineered __

Safety Features (ESP) bus E10. Standby Diesel-Generator #13 loaded as-required, restoring power to Train C. The cause of this event was determined to be lack of attention to work performance methods. An electrician inadvertently-touched the trip contact on the protective-relay in the process of inserting the contact plug. Corrective actions include training of maintenance personne'. revision of appropriate GE relay celibration procedures and' addition of a training objective on the proper method for installing relay contact plugs.

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UCENSEE EVENT REPORT (LER) TEXT CONTINUATION m ovio ous =o ow-em eieaan ov n 7aceptyesaut m CK4 mi f MVue t a 60 44 A toutatlR I6i tafet iM ma " tO." QM South Texas, Unit 1 o p to lo lo l4 j9 ) 8 9 l1 O j Oj 4 0 l0 0l2 or 0 l3 sua m .m m. e - .unww unc o mu v on DESCRIPTION OF EVENI:

On February 1$.1991. Unit I was in its third refueling outage with no fuel in the reactor vessel. At 0259 hours0.003 days <br />0.0719 hours <br />4.282407e-4 weeks <br />9.85495e-5 months <br />, a partial loss of offsite power occurred when the supply breaker to 13.8 kV Standby bus lit tripped during routine maintenance of a phase A overcurrent protection relay. Standby bus 111 supplies offsite power to 4.16 kV Engineered Safety Features (EST) bus E10.

Standby Diesel Oenerator (SDC) #13 loaded as required, restoring power to Train C. At 0327 hours0.00378 days <br />0.0908 hours <br />5.406746e-4 weeks <br />1.244235e-4 months <br />, SDC #13 was secured and all safety systems were reset to normal lineup and configuration.

Two utility electricians were performing preventive maintenance activities on an over current protection relay. Following successful testing of the CE IAC 51/ Sill phase A overcurrent protection relay, the relay was reinstalled into its case located in switchgear 111 cubicle 5. The electricians verified that the trip contacts were open and the induction disc was not in the trip position. Upon insertion of the relay contact plug, which placeu the relay in service, the supply breaker to Standby bus 111 (ST 130) tripped. When the ST 130 breaker tripped the electricians removed the contact plug and relay from its case. An inspection of all contacts and the induction disc was performed. No abnormalities were identified with the relay, case or contact plug.

Following notification to the Shift Supervisor, the electricians reinstalled the relay and itu associated contact plug. Standby bus 111 was reenergized at 0313 hours0.00362 days <br />0.0869 hours <br />5.175265e-4 weeks <br />1.190965e-4 months <br /> with no further incident.

CAUSE OF EVENT; The cause of this event was determined to be lack of attention to work performance methods. It was concluded that the electrician inadvertently touched the trip contact on the protective relay with his finger in the process of inserting the contact plug with the heel of his hand which caused the supply breaker to Standby bus lit to trip open as designed.

ANALYSIS OF FVENT:

Actuation of the Standby Diesel Generator #13 is reportable pursuant to 10CFR50.73(a)(2)(iv). The diesel generator started and loaded as required.

The safety systems functioned as designed. At the time of this event Unit I was in a refueling outage with no fuel in the reactor vessel. There were no adverse safety or radiobgical consequences as a result of this event. This event has no significance with regsrd to the potential for accident initiation or adverse impact on mitigation of an accident.

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'saa 00 P. "'a*,7 South Texas, Unit 1 o p lo lo lo l 4l9 l 8 9l1 - 0l q 4 - Op 0l 3 or 0l3 varw . = =ac s ame.,nri CORRECTIVE ACTIONS:

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

1. Training was conducted for appropriate maintenance personnel stressin6 verification during work performance, attention to detail and proper methods for installing CE Relay contact plugs, i

2. The individual involved in this incident was coached concerning the event. ,

3. Procedures governing calibration of the CE-IAC 51A relays and similar CE relays will be enhanced to include independent verification and caution statements where appropriate. Thf, action will be completed by March 15, 1991.

4. An existing objective.in the Basic Relay electrical maintenance training program has been expanded to include the proper method for installing CE Relay Contact plugs and the necessity of taking the appropriate  !

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ADDITIONAL INV0RMATION:

There have been two previous events reported on Unit i regarding inadvertent Engineered Safety Features actuations due to inattention to sork performance methods.

LER 89 013 Unplanned Engineered Safety Features Actuation of Fuel Handling Building ilVAC Due to Personnel Error.

LER 90 004 Inadvertent Engineered Safety Features Actuation Due ,

to Inadequate Control of Procedure Performance.

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