ML19259C048
| ML19259C048 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 06/06/1979 |
| From: | Brown S VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-PT21-79-133-000 NUDOCS 7906120262 | |
| Download: ML19259C048 (2) | |
Text
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VIRGINI A ELECTRIC AND POWER COMP ANY, RICNMOND, VIRGINI A 23261 June 6, 1979 Mr. James P. O'Reilly, Director Serial No. 455 Office of Inspection & Enforcement PSE&C/WLT:mac: wang U. S. Nuclear Regulatory Conmission Region II Docket No. 50-339 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303
Dear Mr. O'Reilly:
On June 1,1979, a report was made under the provisions of 10CFR50.55(e) concerning an electrical fault which occurred on a Class 1E 480 volt motor control center supplied by Klockner-Moeller Corporation.
A.
Name and address of reporting individual:
Mr. E. A. Baum, Executive Manager Licensing and Quality Assurance 1irginia Electric and Power Company P. O. Box 26666 Richmond, Virginia 23261 B.
Facility, activity, and/or component affected:
North Anna Power Station, Unit 2 Motor Control Center 2-EP-MC-11 (Bus 2J1-1)
C.
Name of firm constructing the facility or supplying the component, activity or service:
Stone & Webster Engineering Corporation 2284 204 P. O. Boy. 2325 Boston, Massachusetts 02107 D.
Description of defect, deficiency, or failure to comply:
On May 16, 1979, an electrical fault occurred on Class 1E 480 volt motor control center 2-EP-MC-11.
Inspection of the motor control center by the supplier's representative, revealed a loose cormection.
on a wire which feeds the control transformer in a cubicle which contained a non-reversing starter.
Klockner-Moeller's representative postulated that the loose connection caused the contactor to chatter, thus producing excessive ionized air.
The ionized air collected in the motor control center cubicle until the air gap betwen 480 volt phases broke down. The air gap break down allowed an arc to generate which produced more ionized air.
The fault thus spread into the vertical and horizontal buses until the 480 volt load center breaker tripped.
Damage to the motor control center was found to include the breaker and starter in the cubicle with the loose connection, the vertical bus in the section where the fault initiated and numerous insulators throughout the motor control center.
7 90612 0 M N O