05000313/LER-1980-022-01, /01T-0:on 800624,w/Mayflower 500 Kv Transmission Line Out of Svc & Unit Operating at Full power,500 Kv Mabelvale Line Tripped.Caused by Ground Fault & Overload. Lock-out Relays Were Reset & 500 Kv Bus re-energized

/01T-0:on 800624,w/Mayflower 500 Kv Transmission Line Out of Svc & Unit Operating at Full power,500 Kv Mabelvale Line Tripped.Caused by Ground Fault & Overload. Lock-out Relays Were Reset & 500 Kv Bus re-energized

ML19320C017
Person / Time
Site:	Arkansas Nuclear
Issue date:	07/07/1980
From:	Shively C ARKANSAS POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19320C008	List: 05000313/LER-1980-022, Forwards LER 80-022/01T-0 05000313/LER-1980-022-01, /01T-0:on 800624,w/Mayflower 500 Kv Transmission Line Out of Svc & Unit Operating at Full power,500 Kv Mabelvale Line Tripped.Caused by Ground Fault & Overload. Lock-out Relays Were Reset & 500 Kv Bus re-energized
References
LER-80-022-01T, LER-80-22-1T, NUDOCS 8007150650
Download: ML19320C017 (5)

LER-1980-022, /01T-0:on 800624,w/Mayflower 500 Kv Transmission Line Out of Svc & Unit Operating at Full power,500 Kv Mabelvale Line Tripped.Caused by Ground Fault & Overload. Lock-out Relays Were Reset & 500 Kv Bus re-energized

Event date:
Report date:
3131980022R01 - NRC Website

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Reportable Occurrence Report No. 50-313/80-022/01T 12.

Report Date: 7/7/80 3.

Occurrence Date: 6/24/80

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. Facility: ' Arkansas Nuclear One --Unit 0ne Russellville, Arkansas S.

Identification of Occurrence:

Conditions arising from natural events, that as a result of the event

-(partial loss of offsite power due to transmission line failure) require a unit shut down and operation of safety systems or other protective measures (ES bus voltage restored by automatic action of Emergency Diesel Generators).

Reportable per T.S.

6.

Conditions ' Prior to Occurrence:

Steady-State Power X

Reactor Power 2568 MWth Hot Standby Net Output-780 MWe Cold Shutdown Percent of Full Power 100 %

Refueling Shutdown Load Changes During Routine Power Operation Routine Startup s0peration Routine Shutdown Operation-Other (specify)

Steady state power operation with the Mayflower 500KV line (one of three 500KV lines) out of service.

7.

Description of Occurrence:

. At 1540 hours0.0178 days <br />0.428 hours <br />0.00255 weeks <br />5.8597e-4 months <br />, switchyard circuit breakers tripped apparently due to a ground fault isolating the Mabelvale.500KV line.

The unit's generation, along with Unit.Two's generation, was transferred to the Fort Smith 500 KV line which. tripped open at the Fort Smith end,-as a result of feeder overload. The Mabelvale line became available again, but did not close R

into the ANO switchyard 500KV ring bus because of inability to sync-check.

The Morrilton East-161KV line-tripped on overload, following Unit Two's

. Reactor / Turbine trip, leaving only the 500K7 bus segment feeding the

.autotransformer and the Russellville East 161XV line carrying power generation.

Startup transformer #1 remained energized from the auto-transformer and startup transformer #2 remained tied to the 161KV bus.

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Reportable Occurrence No. 313/80-022/01T

. Description of Occurrences (Continued):

A manual runback of reactor power was initiated following an automatic.

runback of generator output.

The reactor / turbine subsequently tripped,

- and' auxiliary loads transferred to startup transformer #1 which was.already experiencing 'a low output voltage.

The auto transformer bank received lockout relay operation from an apparent-faulted relay, resulting in lockout relay-operation of startup transformer #1 (and Unit Two's startup transformer

1. 3), placing both units without auxiliary bus voltage.

At this point, the switchyard-busses were de-energized except for the Russellvillle East tie to startup? transformer #2 (one source of offsite power), which remained energized.

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Reportable Occurrence Report No. 50-313/80-022/01 T 8.

Designation of Apparent Cause of Occurrence:

Design Procedure.

Manufacture Unusual Service Condition y

Including Environmental

. Installation /-

Construction.-

Component Failure -

X (See Failure Data)

Operator Other (specify)-

Occurrence was caused by a loss of offsite transmission linetand aggravated by the resultant grid degradation.

9.

Analysis of Occurrence:

Coincident with the lock-out relay operation of Esartup transformer #1, both 'Dnergency Diesel Generators auto-started and re-energized ES buses A-3 and A-4.

At about 65 minutes from occurrence initiation, house loads were begun to.be ' sequenced back to Startup transformer #1.

The Reactor Coolant Pumps were sequenced on.

The reactor was fed by natural circulation.for approximately 100 minutes.

The final

- plant conditions was hot standby.

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{J Reportable ~0ccurrence. Report-No. _50-313/80-022/01 T

10. -Corrective Action:

AP&L Transmission line fault was clear 5d.

No plant site corrective action required as all plant systems operated per design.

11.

Failure Data:

Not applicable.

4