05000339/LER-1980-018-03, /03L-0:on 800602,loss of C Reserve Station Svc Transformer Occurred Rendering C Normal Station Svc & 2G Intake Structure Buses Inoperable.Caused by Open Breakers. Emergency Buses Energized & Breakers Closed

/03L-0:on 800602,loss of C Reserve Station Svc Transformer Occurred Rendering C Normal Station Svc & 2G Intake Structure Buses Inoperable.Caused by Open Breakers. Emergency Buses Energized & Breakers Closed

ML19326D779
Person / Time
Site:	North Anna
Issue date:	07/01/1980
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19326D775	List: 05000339/LER-1980-018, Forwards LER 80-018/03L-0 05000339/LER-1980-018-03, /03L-0:on 800602,loss of C Reserve Station Svc Transformer Occurred Rendering C Normal Station Svc & 2G Intake Structure Buses Inoperable.Caused by Open Breakers. Emergency Buses Energized & Breakers Closed
References
LER-80-018-03L, LER-80-18-3L, NUDOCS 8007030288
Download: ML19326D779 (2)

LER-1980-018, /03L-0:on 800602,loss of C Reserve Station Svc Transformer Occurred Rendering C Normal Station Svc & 2G Intake Structure Buses Inoperable.Caused by Open Breakers. Emergency Buses Energized & Breakers Closed

Event date:
Report date:
3391980018R03 - NRC Website

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U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT CONTROL BLOCK / / / / / / / (1)

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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OU E DOCKET l' BER EVENT DATE REPORT DATE EVENT DESCRIPTION AND PROL d CONSEQUENCES (10)

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On May 29, 1980, during Mode 3 operation, loss of the "C" Reserve Station

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Service Transformer occurred rendering the "C" normal station service and 2G

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intake structure buses inoperable.

Since emergency diesel generators were

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immediately started to energize necessary emergency buses, the health and

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safety of the general public were not affected.

This event is reportable

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pursuant to T.S. 6.9.1.9.b.

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SYSTEM

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CAUSE COMP.

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SEQUENTIAL OCCURRENCE REPORT REVISION LER/R0 EVENT YEAR REPORT NO.

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ACTION FUTURE EFFECT SHUTDOWN ATTACHMENT NPRD-4 PRIME COMP.

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (27)

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This event occurred because test personnel mistakenly opened t!e unit 1 genera-/

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tor output breakers which tripped and blacked out the 34.5 KV feed to the "C"

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/___RSS Transformer.

The 1H and 2J emergency buses were immediately energized

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oy the starting of their respective diesel generators.

After the generator

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output breakers were reclosed, the diesels were unloaded and secured.

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FACILITY METHOD OF STATUS

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NRC USE ONLY

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d-l Virginia Electric and Power Company North Anna Power Station, Unit #2

Attachment:

Page 1 of 1 Docket No. 50-339 Report No. LER 80-018/03L-0

Description of Event

On May 29, 1980, with the unit in a hot standby conditian, loss of the "C" Reserve Station Service (RSS) Transformer occurred v hich rendered the 4160 volt "C" normal station service buses and 2G intake structure bus inoperable. This event-is contrary to T.S. 3 1.1.1 and reportable pursuant to T.S. 6.9.1.9.b.

Probable Consequences of Occurrence Prior to startup, the reserve station service transformers are used to power auxiliaries and then during startup are used to deliver power to the necessary systems. Once the unit's generator is on line, the transformers feed only the emergency and intake bases.

Because emergency buses, capable of powering the necessary safety related equipment, were immediately energized by starting the appropriate emergency diesel generators upon loss of the "C" RSS Transformer, the consequences of the event were minimal and the health and safety of the general public were not affected. There are no generic implications associated with this occurrence.

Cause of Event

The loss of the "C" Reserve Station Service Transformer occurred because test personnel failed to follow their approved procedure and mistakenly opened the output breakers for the Unit I generator instead of the Unit 2 generator which tripped and blacked out the 34.5 KV feed to the transformer.

Immediate Corrective Action

The 1H and 2J Emergency Diesel Generators were immediately started to energize their respective emergency bus. The "C" Reserve Station Service Transformer and its associated buses were then restored by reclosing the Unit 1 generator output breakers and unloading the diesel generators accordingly.

Scheduled Corrective Action No scheduled corrective action is required.

Actions Taken to Prevent Recurrence The A&C test personnel involved were informed of their mistake and instructed to follow test procedures as written.

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