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Omaha Public Power District -1623 HAMNEY * OMAHA, NE5RASMA $5103 e T E L E PHO N E 63n.4000 AMCA CODF 40J

March 20, 1980

Director of Nuclear Reactor RegulationATTN: Mr. Robert W. Reid, ChiefOperating Reactors Branch No. 4U. S. Nuclear Regulatory ConinissionWashington, D. C. 20555

Reference: Docket No. 50-285

Gentlemen:

The Commission's letter of October 17, 1979, to the Omaha PublicPower District requested information regarding loss of offsite power andthe attendant effects on grid voltage and frequency at the fort CalhounS ta ti on. Provided herewith is the District's response to that request.The attached report includes a description of all loss 'f offsite powerevents that have occurred at Fort Calhoun Station Unit 1.

Sincerely,.*\,

i \; ([ Y 6 . -fW. C. JonesDivision ManagerProduction Operations

WCJ/KJM/BJil/TLP:jnin

Attach,

cc: LeBoeuf, Lamb Leiby & MacRae1333 New Hampshire Avenue, N. W.Washington, D. C. 20036

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s0032 60677

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ATTACHMENT

The network interconnections and the in-plant distribution systemsfor the Fort Calhoun Station Unit No. I are described in detail insection 8 of the FSAR. This response supplements that information.

Attached is a circuit diagram showing the 345 KV (Sub 3451) and 161KV (Sub 1251) substations at the Fort Calhoun Station. Also shown arethe circuits that interconnect these substations with the transmissiongrid. This diagram should be used in place of Figure 8.2-1 of the FSARbecause some additional substations and circuits have been placed intoservice since the FSAR was published.

Circuit outage data was reviewed in order to determine the totalnumber of loss of off-site power events that have occurred since theunit began operation in August,1973. Only forced outages were con-sidered, since the transients induced by such outages will bound thoseinduced by scheduled outages. Outage data was accumulated for circuits3422, 3423, 3424, 2431, and 1588. Since the 161 KV feed to Sub 1251 isradial from Sub 1226, outage data was also accumulated for circuits 1533and 1566 because outages of these circuits could result in surges incircuit 1588.

A review of plant outage reports, control room logs, and stripcharts was conducted in an attempt to correlate plant conditions withthe circuit outage data. Sufficient data to adequately address thequestions regarding voltage and frequency fluctuations does not exist.For example, there are no voltage recorders on the 4160 volt plantbuses. In addition, there is no 161 KV bus voltage recorder, and the345 KV bus voltage recorder was not operational until 1976. Also, thestrip charts for voltage, frequency, and generator output are not re-quired to be retained for the life of the unit and some of them couldnot be located.

The 345 KV and 161 KV voltage levels are not interconnected atSubstation 3451/1251. They can be interconnected at the 4160 volt levelin the plant, but this is not the normal operating condition. Thus, atthe Fort Calhoun Station, disturbances in one transmission system arenot necessarily reflected in the other. In most cases, it is impossibleto draw conclusions from the data that is available.

A worksheet was prepared for each loss of off-site power eve .Each worksheet contains information about the type of event, date andtime of occurrence and circuit restoration, which circuits were in-volved, and the cause of the event. To the extent possible, the effectson the plant buses were evaluated. The completed worksheets are attached.

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Two of the questions regarding losses of all off-site power areanswered below, rather than on the worksheets.

2. If a turbine. trip occurred, how soon after did loss of off-site power occur?

A review of the total loss of off-site power events shows thatthey resulted from conditions external to the plant, ratherthan from turbine trips caused by internal conditions. Inaddition, it should be noted that the turbine generator isequipped with an anticipatory trip on loss of off-site power.

3. -If power was recovered promptly (10 minutes or less), was itdue to automatic or manual actions?

All restorations from loss of off-site power at the Forti Calhoun Station are manual.

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Loss of Off-Site Power Event

Type: Partial (161 KV)

Date/ Time of Occurrence: September 25, 1973/11:57 p.m.

Date/ Time of Restoration: September 26, 1973/6:45 a.m.

Circuits Involved: 1588: - .

Cause of Event: OCB #111 at Sub 1251 locked open due to storm in area.The breaker was reclosed the following morning from the control room.

Effects on Plant Buses: Fast transfer of buses 1A3 and 1A4 to generatorauxiliary transformers occurred successfully. Unit continued in operation.No effects on generator voltage were apparent. This is the only avail-able chart. Both diesel generators started and ran up to idle speed.They were secured by Operations when it was apparent that they would not

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' Type: -Partial (345 KV)

Date/ Time of Occurrence: September'25, 1973/11:57 p.m.

P ' Date/ Time of Restoration: September 26, 1973/11:59 p.m.

Circuits Involved: 3424I

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Circuit outage caused by storm in area. BreakerCause of Event:reclosed by supervisory control.

Effects on Plant Buses: No effects on generator voltage were apparent.This is the only chart available.

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Date/ Time of Occurrence: December 20, 1973/11:58 a.m.

Date/ Time of Restoration: ' December 20, 1973/8:53 p.m.

Circuits Involved: 3424

Cause of Event: Circuit outage caused by phase to ground fault due todowned shield wire at structure #215.

Effects on Plant Busei: The generator voltage chart showed'a 500 voltdecreasing spike. This is the only chart available. The unit continuedin operation. The event is noted in the control room 109

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Type: Loss of 161 KV integrity at Sub 1226

Date/ Time of Occurrence: May 10, 1974/7:31 p.m.

Date/ Time of Restoration: May 10, 1974/7:31 p.m.


Cause of Event: Momentary outage. Cause unknown.

Effects on Plant Buses: Buses 1A1, lA2, 1A3, and 1A4 were all being fedfrom the house service transformers (161 KV) at the time of the event.All buses successfully fast-transferred to the generator auxiliarytransformers. Buses IA3 and 1A4 were manually transferred to the 161 KVsource at 10:21 p.m. on May 10, 1974. No strip charts are available.Normal unit operation continued.

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Type: Loss of 161 KV integrity at Sub 1226 -



Circuits Involved: -1566


Effects on Plant Buses: "All buses were being fed from the generatorauxiliary transformers at the time of this event. (See previous event.)

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Effects on Plant Buses: Generator voltage - 500 volt decreasing spike.Generator watts - 20 MW spike. (Only charts available.) The unitcontinued in operation. There is no control room log entry for thisevent.

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; Loss of Off-Site Power Event

Type: -Partial (345 KV)

Date/ Time of Occurrence: August 8, 1974/5:05 p.m.I

Date/ Time of Restoration: August 8, 1974/5:05'p.m.



Effects on Plant Buses: Generator watts - 10 MW spike. Generatorvoltage - 200 volt decreasing spike. (Only charts available.) The unit4continued in operation. There is no control room log entry.

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Date/ Time of Occurrence: August 13, 1974/10:41 a.m.

Date/ Time of Restoration: August 13, 1974/11:39 a.m.


Cause of Event: Circuit outage caused by storm in area.

Effects on Plant Buses: Generator watts -20 MW spike. Generatorvoltage - 500 volt decreasing spike. (Only charts available.)

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The unit tripped at 10:49 a.m. from 385 MW due to APD trips on RPS,

channels A and D. The RPS trips were spurious and were caused by the-vio ent e ectr cal storm in the area. The unit returned to service atl l i5:23 a.m. on August 14, 1974.

At the time of the trip, bus 1A2 failed to fast-transfer to the 161 KVsource. A faulty relay was replaced.

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Date/ Time of Occurrence: ~ January-29, 1975/11:11 a.m.

Date/ Time of Restoration: January 29, 1975/11:15 a.m.


Cause of Event: Outage caused by Iowa Public Service personnel workingon metering at the Raun Substation.

Effects on Plant Buses: Generator MVAR - 15 MVAR spike. (Only chartavailable.) The unit continued in operation. _ The event is noted in thecontrol room log.

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Type: Partial (345'KV)'

Date/ Time of Occurrence: February 28, 1975/8:07 a.m.

Date/ Time of- Restoration: . February 28, 1975/8:07 a.m.

Circuits Involved: :3431

Cause of Event: PCB #4 was cleared for maintenance. PCB #2 tripped andreclosed due to a flashover at the Raun Substation caused by contamin-ation.

' Effects on Plant Buses: The unit was shutdown for refueling at the timeof the event. No plant data is available, and there are no control roomlog entries for this event.

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Date/ Time of 0ccurrence: March 1 1975/2:25 a.m.

Date/ Time of Restoration: March 1, 1975/2:32 a.m.


Cause of Event: With PCB #4 cleared for maintenance, PCB #2 tripped andlocked out due to a flashover at-the Raun Substation caused by contamin-ation.

Effects on Plant Buses: The unit was out of service for refueling atthe time of the event. No plant data is available, and there are nocontrol room log entries for this event.

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Date/ Time of Occurrence: March 1, 1975/3:34 a.m.

Date/ Time of Restoration: March 1, 1975/3:34 a.m.

- Circuits Involved: 3431

Cause of Event: Momentary outage of PCB #2 with PCB #4 cleared for4maintenance. Probable flashover at the Raun Substation due to con-tamination.

Effects on Plant Buses: See notes for event at 2:25 a.m.

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Type: Partial (345 Kt';

Date/ Time of Occurr9c ; 'Drch 1, 1975/4:56 a.m.

Date/ Time of Reste Om f(arch 1,.1975/4:56 a.m.r

Circuits Involveh ?hy,

Cause of Event: /kAentary outage of PCB #2 with PCB #4 cleared formaintenance. Probable flashover at the Raun Substation due to con-tamina tion,

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Effects on Plant Buses: See notes for event at 2:25 a.m.

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Type: Total

.Date/ Time of Occurrence: March 13, 1975/12:29 a.m.

Date/ Time of Restoration: March 13, 1975/11:34 a.m. ~


Cause of Event: With circuit 1588 out of service for maintenance ofthe house service transformers, PCB's #4 and #5 (circuit 3423) tr'. gedidue to faulty actuation of the fault pressure relay on the generatormain transformer. The misoperation was caused by water in a junctionbox.

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Loss of Off-Site Power Event!


Date/TimeLof Occurrence: March 17, 1975/2:32 p.m.

Date/ Time of Restoration: March 17,1975/2:37 p.m..


Cause of Event: PCB #4 tripped and locked out with PCB #2 cleared formaintenance. Caused by telephone company.,

Effects on Plant Buses: .The unit was out of service for refueling atthe time of the event. No plant data is available. The event is notedin the control room log.

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Date/ Time of Occurrence: April 7,1975/10:55 a.m.

Date/ Time of Restoration: April 7,1975/11:07 a.m.

Circuits Irvolved: 3431

Cause of Event: Trip caused by IPS technicians at the Raun Substation.Breakers closed by supervisory control.

- Effects on Plant Buses: The unit was out of service for refueling atthe time of this event. No plant data is available. The event is notedin the control room log.

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Date/ Time of Occurrence: April 22, 1975/10:14 p.m.

Date/ Time of Restoration: April 22, 1975/10:14 p.m.

- Circuits' Involved: 3431- 1

Cause of Event: PCB's #2 and #4 locked open. Cause unknown. Closed by |supervisory control. j

Effects on Plant Buses: The unit was out of service for refueling at~

. the time of this event. No plant data is available. The event is notedin-the control room log.

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- Type: Partial (345 KV)

Date/ Time of.0ccurrence: June 3, 1975/11:42 a.m.

Date/ Time of Restoration: June 3, 1975/11:42 a.m.


Cause of Event: PCB's #2 and #4 locked open. . Caused by operation atthe Raun Substation. Closed by supervisory control.

Effects on Plant Buses: Generator voltage - very slight discontinuity.Generator MVAR - gradual decrease of 10 MVAR between 11:40 a.m. and 1:15p.m. The unit continued in operation. There is no control room logen try.

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1 Type: -Partial (345 KV)

Date/ Time of Occurrence: June 3, 1975/1:53 p.m.

Date/ Time of Restoration: June 3, 1975/5:20 p.m.


Cause of Event: PCB's #2 and #4-locked open. Caused by operation atthe Raun Substation. Closed by supervisory control after investigation.

Effects on Plant Buses: Generator voltage - no noticeable effect. Theunit continued in operation. The event is noted in the control roomlog.

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Type: Partial (345 KV)'

Date/ Time of Occurrence: November 9, 1975/10:18 a.m.

Date/ Time of Restoration: November 9, 1975/10:26 a.m.


Cause of Event: Cause unknown. PCB #5 closed by supervisory control at10:26 a.m. PCB #6 closed by supervisory control at 3:40 p.m.

Effects on Plant Buses: Generator MW - no effect. Generator MVAR - noeffect. The unit continued in operation. The event is noted in thecontrol room log.

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Loss of Off-Site Power Event.

Type: - Partial (345 KV)

Date/ Time of Occurrence: December 9, 1975/12:01 p.m.

Date/ Time of Restoration: December 9, 1975/12:09 p.m.


Cause of Event: Cause of outage unknown. Breakers closed successfully.

Effects on Plant Buses: Generator NW - 10 MW decreasing spikes whenbreakers tripped and reclosed. Generator MVAR - 5 MVAR decreasing stepchange when breakers tripped. Stayed at that value when breakers werereclosed. The unit continued in operation. The event is noted in thecontrol room log.

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Date/ Time of Occurrence: December 27, 1975/11:56 a.m.

Date/ Time of Restoration: December 27, 1975/12:01 p.m.


Cause of Event: PCB's #2 and #4 locked out following the loss of a unitat IPS George Neal Station.

Effects on Plant Buses: Generator MW - +15 MW spike at time of trip.Generator MVAR - several spikes, but none at the exact time of the trip.Generator volts - no effect. The unit continued in operation. There isno control room log entry.

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Type: Loss of 161 KV integrity at jub 1226

Date/ Time of Occurrence: January 7, 1976/11:59 a.m.

Date/ Time of Restoration: anuary 7, 1976/12:06 p.m.


Cause of Event: Circuit 1533 tripped at Sub 1209 by an electricianworking in the panel.

Effects on Fiant Buses: Generator MW - +10 MW spikes when the breakerstripped and reclosed. The unit continued in normal operation. There isno control room log entry.

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Type: Total


Date/ Time of Restoration: February 21, 1976/3:28 a.m.

Circuits Involved: 1588 and 3423

Cause of Event: Circuit 1588 tripped due to a phase-to-phase fault,

caused by a storm in the area. Fast transfer of buses 1A3 and 1A4failed, and the unit tripped on low RCS flow.

Effects on Plant Buses: All AC power, except instrument buses, waslost. Both diesel generators started automatically and were loaded byOperations. The 345 KV voltage chart shows a 45 KV negative spike atthe time of the trip. This is the only data available.

A faulty Agastat relay in the fast transfer circuit was replaced.

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Date/ Time of Occurrence: March 29, 1976/10:43 p.m.

Date/ Time of Restcration: March 30, 1976/3:23 a.m.


Cause of Event: Failure of bushing on OCB #4 at Sub 1226 with OCB #6already open due to a previous flashover. Fast transfer of buses 1A3,and 1A4 was completed, and no unit outage occurred.

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Effects on Plant Buses: Diesel generator 1 started automatically. D2did not, so it was started by Operations to prove its operability. The161 KV system was returned to service with the fast transfer schemedisabled until further tests were completed.

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The unit was out of service at the time of the event for incore detectorreplacement, and no plant data is available.

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Date/ Time of Occurrence: May 28, 1976/8:37 a.m.

Date/ Time of Restoration: May 28, 1976/8:48 a.m. (partial)

Circuits Involved: 3422, 3423, and 3424

Cause of Event: PCB's #5 and #6 were opened to isolate circuit 3424.PCB #2 tripped due to the loss of bus potential to the line relays.This"resulted in a transient due to partial load rejection. The reactortripped on high pressurizer pressure, tripping the turbine and PCB #4.The generator disconnect was opened, and PCB #2 was closed at 8:48 a.m.and PCB #4 was closed at 9:45 a.m.

Effects on Plant Buses: 345 KV voltage - +15 KV spike followed by unittrip. Generator MVAR - +50 MVAR spike followed by unit trip. Buses 1A1and 1A2 fast transferred to the house service transformers (161 KV).Both diesel generators started and came up to idle speed automatically.They were secured at 10:01 a.m. The unit returned to service at 9:52p.m. on May 28, 1976.

As a result of this incident, the line relays for circuit 3422 werereset from 537 to 717 MVA and the potential circuit was modified.

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Type: ' Partial (161 KV)




Cause of Event: Momentary kick out of circuit 1588 caused by flashoverof R phase lightning arrestor at Sub 1226 due to bird contamination.

Effects on Plant Buses: Generator MW - +10 MW spike. Generator MVAR -+20 MVAR spike. Operation then continued at 10 MVAR lagging instead of0. Buses 1A3 and 1A4 fast transferred to the generator auxiliarytransformers, and the unit continued in operation. Diesel generator #1started ar.d came up to idle speed. D2 did not start automatically, so

; it was started by Operations to prove that it was operable. The systemwas returned to normal at 8:37 p.m.

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Date/ Time of Occurrence: February 23, 1977/6:03 p.m.



Cause of Event: Circuit outage caused by cross-arm failure at structure#87 (192rd Street and Highway 92). Disconnects SW and 6E were openedand PCB's #5 and #6 closed at 9:08 p.m. on February 23, 1977. Systemreturned to normal at 8:38 a.m. on February 24, 1977.

Effects on Plant Buses: Generator MW - +15, -10 MW spike at time of- trip. Normal unit operation continued. The event is noted in the

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Date/ Time of Occurrence: April 17,1977/8:33 p.m.

Date/ Time of Restoration: April 17,1977/8:33 p.m.


Cause of Event: Momentary outage caused by lightning.

Effects on Plant Buses: Generator MVAR +20 MVAR spike. Normal unitoperation continued. The event is noted in the control room log.

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. Type: Partial (345 KV)

Date/ Time of Occurrence: June 28, 1977/12:09 a.m.1

Date/ Time of Restoration: June 28, 1977/12:14 a.m.


Cause of Event: Circuit outage caused by storm in area.

Effects on Plant Buses: Generator MW - +10 to 20 MW spikes when breakerstripped and reclosed. Generator MVAR - +15 MVAR spike when breakerstripped; +15 MVAR spike when breakers reclosed. Normal unit operationcontinued. The event is noted in the control room log.

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Type: Total

Date/ Time of Occ'urrence: August 2" 1977/10:53 a.m.

Date/ Time of Restoration: August 22, 1977/10:53 a.m. for circuit 1588/12:43 p.m. for circuit 3423on backfeed

Circuits' Involved: 1588 and 3423

Cause of Event: Circuit 1588 tripped and reclosed due to faulty relaysat Substation 1226. Fast transfer of buses 1A3 and 1A4 failed, and theunit tripped due to low RCS flow.

Effects on Plant Buses: Generator MW - unit trip from 465 MW. Gener-ator MVAR - inconclusive. 345 KV voltage - inconclusive. The dieselgenerators started automatically and were loaded by Operations. They.were shutdown at 12:39 p.m. The unit returned to service at 11:30 a.m.

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on August 23, 1977.

A defective relay target reset device was replaced at Substation 1226.o

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Loss of-Off-Site Power Event


Date/ Time of Occurrence: September 2, 1977/12:32 a.m.r

Date/ Time of Restoration: September 2, 1977/12:32 a.m.



Effects on Plant Buses: 345 KV voltage - several spikes at approxi-mately 12:30 a.m. The largest was -35 KV. Generator MW - severalspikes ranging from +5 to +20 MW. Generator MVAR - several spikes.The largest was +15 MVAR. Normal unit operation continued. There is nocontrol room log entry.>

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Type: Loss of'161 KV integrity at Sub 1226

; Date/ Time of Occurrence: September 8, 1977/8:36 p.m.

1 - Date/ Time of Restoration: September 8, 1977/8:36 p.m.

Circuits Invol' ed: 1533v

Cassa of Event: Momentary outage due to lightning in the area.

Effs.ts on Plant Buses: Generator MW - +5 MW spike. Generator MVAR -inco clusive. No ink on chart. Normal unit operation continued. Thereis no control room log entry.

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Date/ Time of Occurrence: February 7, 1978/7:59 a.m..

Date/ Time of Restoration: Februa ry_ 7, 1978/7:59 a.m.


Cause of Event: Momentary outage caused by flashover of circuit 1534LAt MOD at Sub 1209.

Effects on Plant Buses: Generator MW - no effect. Generator MVAR - noeffect. Normal unit operation continued. There is no control room logentry.

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Date/ Time of Occurrence: February 10, 1978/11:23 p.m..

Date/ Time of Restoration: February 11, 1978/1:49 a.m.,

Circuits Involved: PCB #6, Sub 3451| ,

Cause of Event: Breaker tripped due to low gas pressure.

Effects on Plant Buses: No data is available. The event is not notedin the control room log.

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Type: ' Partial (345 KV)





Effects on Plant Buses: .The unit was out of service at the time of thisevent. 345 KV voltage - 62 KV spike. There is no control room logentry.

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Type: ' Partial (345 KV)-

: ' Date/ Time of Occurrence: June 22, 1978/2:16 p.m.

Date/ Time of Restoration: June 22, 1978/2:16 p.m.I

Circuits Involved: PCB #5, Sub 3451


Effects on Plant Buses: 345 KV voltage - +8 KV spike. Normal unitoperation continued. The event is noted in the control room log.

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Date/ Time of Occurrence: October 19, 1978/11:28 a.m.

Date/ Time of Restoration: October 19, 1978/11:28 a.m.


Cause of Event: Momentary outage due to lightning arrestor failure oncircuit 1534 at Sub 1234.

J Effects on Plant Buses: Unit out of service for refueling. No plantdata is available. There is no control room log entry.

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Date/ Time of Occurrence: November 20, 1978/10:54 a.m.

Date/ Time of Restoratio n: November 20, 1978/10:54 a.m.



Effects on Plant Buses: Unit out of service for refueling. No plantdata is available. There is no control room log entry.

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Date/ Time of Occurrence: September 8, 1979/11:24 p.m.

Date/ Time of Restoration: September 9, 1979/9:39 p.m.-

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Cause of Event: Outage was caused by a line to ground fault due to a,downed shield wire between structures #126 and #127. The ring bus wasrestored at 1:32 a.m. on September 9,1979, after opening a disconnect.The circuit was restored at 9:39 p.m. on September 9, 1979.*

Effects on Plant Buses: 345 KV voltage - 23 KV spike. GeneratorMVAR - +30 MVAR spike. Unit operation continued at 110 MVAR lagging.It had been 90 MVAR prior.to the event.

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bh Et L- · 2019. 11. 16. · Cause unknown. Effects on Plant Buses: Buses 1A1, lA2, 1A3, and 1A4...

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