Information Notice 1988-75, Disabling of Diesel Generator Output Circuit Breakers by Anti-Pump Circuitry

Disabling of Diesel Generator Output Circuit Breakers by Anti-Pump Circuitry

ML031150110
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	09/16/1988
From:	Rossi C E Office of Nuclear Reactor Regulation
To:
References
IN-88-075, NUDOCS 8809120197
Download: ML031150110 (8)

I UNITED STATES NUCLEAR REGULATORY

COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 September

16, 1988 NRC INFORMATION

NOTICE NO. 88-75: DISABLING

OF DIESEL GENERATOR

OUTPUT CIRCUIT BREAKERS BY ANTI-PUMP

CIRCUITRY

Addressees

All holders of operating

licenses or construction

permits for nuclear power reactors.

Purpose

This information

notice is being provided to alert addressees

to potential problems where the capability

to either automatically

or manually close diesel generator

circuit breakers from the control room may be lost. It is expected that recipients

will review the information

for applicability

to their facilities

and consider actions, as appropriate, to avoid similar problems.

However, suggestions

contained

in this information

notice do not constitute

NRC requirements;

therefore, no specific action or written response is required.Description

of Circumstances:

On June 5, 1988, operators

at Browns Ferry Unit 3 were unable to reclose the diesel generator

output breakers to the 4-kV shutdown boards from the control room during a loss-of-power/loss-of-coolant-accident (LOP/LOCA)

test. During the test, the output breakers connected

the diesel generators

to their respec-tive 4-kV shutdown boards after the LOP signal was generated;

however, the breakers tripped and remained open after receiving

the LOCA signal. Operators diagnosed

the output breaker lockout problem using system electrical

configu-ration drawings.

An operator was sent to the 4-kY shutdown board to manually transfer output breaker control power to its alternate

source. This momentarily

removed power, enabling the breaker to close when the power was restored.On October 14, 1987, an operator at Wolf Creek Generating

Station manually tripped the output circuit breaker of the emergency

diesel generator (EDG)from the control room. At the time, the EDG was supplying

a vital bus. When the operators

tried to reenergize

the vital bus from the still-operating

EDG, they found that they could not close the EDG output breaker from the control room. The vital bus was finally reenergized

from the offsite power supply.Through examination

of the breaker control schematics

the licensee later found that the EDG circuit breaker could be closed by cycling the EDG mode switch at the EDG local control station.880920197 IN 88-75 September

16, 1988 Discussion:

The anti-pump

circuit configuration

will protect large breakers from rapid cycling and, under certain circumstances, will prevent breaker closure. At Browns Ferry Unit 3, a unique sequence of events, a LOP signal followed within 6 seconds by a LOCA signal, led to the discovery

of a design deficiency

of this circuit configuration.

Contacts from the undervoltage

relay will seal in the breaker anti-pump

relay until the undervoltage

condition

on the 4-kV boards clears.The circuit is designed such that following

a LOP, the undervoltage

condition must exist for at least 5 seconds and the diesel. must reach rated speed before the diesel generator

output breaker will close on the bus. Once the breaker has closed, the closure spring recharge motor and the breaker anti-pump

relay will be energized.

A fully discharged

closure spring requires 2 seconds for the spring to be fully recharged.

During this 2 second window the anti-pump coil will remain energized

via contacts sensing spring position, and if an undervoltage

condition

exists on the 4-kY bus it will seal in and lock open the breaker.During the Browns Ferry event, the EDG output breaker closed 5 seconds after the LOP signal, the undervoltage

condition

was eliminated, and the undervoltage

relay began its 5 second cycle to reset from the undervoltage

condition.

About 1.5 seconds 1ater. the. LOCA-signaL-retr-ipped-the-breaker-and-created-another--

undervoltage

condition

on the 4-kV bus. At this point, because the undervoltage

relay had not completed

its reset cycle, the undervoltage

relay remained in its undervoltage

state. Therefore, the undervoltage

relay sealed in the still-energized

anti-pump

relay because the undervoltage

condition

occurred before the breaker charging spring was fully charged. Thus, the breaker could not be closed from the control room either manually or automatically

until control power was removed, which deenergized

the anti-pump

relay.The Browns Ferry licensee modified the breaker control logic to prevent the anti-pump relay from sealing in during a LOCA condition

by adding a time-delay

relay in the breaker trip coil circuitry.

This relay will be energized

by a LOCA signal and its contact in the anti-pump

coil seal-in path will open after a 2-to 5-second delay to prevent anti-pump

coil seal-in and breaker lockout.The Wolf Creek EDG output circuit breaker has automatic

closing logic to close the circuit breaker when the following

five permissives

are satisfied:

(1) Both offsite circuit breakers are open'(2 The EDG mode switch is in the automatic

mode.(3 Lockout relays are deenergized.

(4 A 3-second time delay has elapsed.(5) The EDG has reached operating

speed and voltage.This logic sends a constant close signal to the circuit breaker that keeps the breaker's

internal anti-pump

relay energized

as long as the logic permissives

are satisfied.

The anti-pump

relay prevents the circuit breaker from cycling if attempts are made to hold the breaker closed against a valid trip signal.I',

IN 88-75 September

16, 1988 When the Wolf Creek operator manually tripped the EDG output breaker, the auto-matic closing logic permissives

remained satisfied.

Therefore, the anti-pump relay remained energized, preventing

reclosure

of the circuit breaker. Cycling the EDG mode control switch at the local control station allowed the circuit breaker to reclose by momentarily

interrupting

the automatic

close signal, there-by resetting

the anti-pump

logic. When the mode switch contact was reclosed by returning

the switch to the "auto' position, the circuit breaker's

automatic closing logic closed the breaker.The Wolf Creek licensee modified the EDG breaker control switch located in the control room to enable the operator to reclose the EDG circuit breaker from the control room. This switch was originally

intended only as a means of paralleling

the EDG with the offsite power supply. With the current modification, the switch can be used to reset the anti-pump

logic and allow the automatic

circuit to re-close the breaker. The modification

added a contact that is closed in the "normal" position and open in the "trip" and "pull to lock" positions

of the control switch.When operators

manually trip the EDG circuit breaker from this control switch, the contacts open to interrupt

the close circuit and reset the circuit breaker anti-pump

relay. If the operator wishes to keep the breaker open, he must put the switch in the "pull to lock" position.

Returning

the switch to the "normal" position completes

the automatic

close circuit and the breaker recloses.It should be noted that although the above discussion

has dealt only with EDG output- circuit breakers, anti-pump

circuit problems could also apply to other breakers that use automatic

closing logic, such as load-sequencing

breakers and offsite supply breakers to the emergency

buses.The information

herein is being provided as an early notification

of a potentially

significant

matter that is still under consideration

by the NRC staff. If NRC evaluation

so indicates, specific licensee actions may be requested.

No specific action or written response is required by this information

notice.If you have any questions

about this matter, please contact one of the technical contacts listed below or the Regional Administrator

of the appropriate

regional office.Di rector Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

Contacts:

James Lazevnick, NRR (301) 492-0814 Carl Schulten, NRR (301) 492-1192 Fred Burrows, NRR (301) 492-0783 Attachment:

List of Recently Issued NRC Information

Notices

Att"aant IN 88-75 September

16, 1988 Page I of I LIST OF RECENTLY ISSUED NRC INFORMATION

NOTICES Notice No. Subject Issuance 88-74 Potentially

Inadequate

9/14/88 Perfornance

of ECCS in PWRs During Recirculation

Operation

Following

a LOCA 88-73 Direction-Dependent

Leak 9/8/88 Characteristics

of Containment

Purge Valves 88-72 Inadequacies

in the Design 9/2/88 of dc Motor-Operated

Valves 88-71 Possible Environmental

9/1/88 Effect of the Reentry of COSMOS 1900 and Request for Collection

of Licensee Radioactivity

Measurements

Attributed

to That Event 88-70 Check Valve Inservice

8/29/88 Testing Program Deficiencies

88-69 Movable Contact Finger 8/19/88 Binding in HFA Relays Manufactured

by General Electric (GE)88-48, Licensee Report of Defective

8/24/88 Supplement

I Refurbished

Valves 88-68 Setpoint Testing of Pres- 8/22/88 surizer Safety Valves with Filled Loop Seals Using Hydraulic

Assist Devices 88P67- -P-F Zfiiairy Fiedeaer Pump 8/Z2j88 Turbine Overspeed

Trip Failure OL

• Operating

License CP

• Construction

Permit Issued to All holders of OLs or CPs for W and 8&W-designei

nuclear power reactors.All holders of 0Ls or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors, fuel cycle licensees, and Priority I material licensees.

All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors._UNITED STATES NUCLEAR REGULATORY

COMMISSION

WASHINGTON, D.C. 20555 OFFICIAL BUSINESS PENALTY FOR PRIVATE USE, $300 FIRST CLASS MAIL POSTAGE & FEES PAID USNRC PERMIT No. 0-57 IN 88-75 September

16, 1988 When the Wolf Creek operator manually tripped the EDG output breaker, the auto-matic closing logic permissives

remained satisfied.

Therefore, the anti-pump relay remained energized, preventing

reclosure

of the circuit breaker. Cycling the EDG mode control switch at the local control station allowed the circuit breaker to reclose by momentarily

interrupting

the automatic

close signal, there-by resetting

the anti-pump

logic. When the mode switch contact was reclosed by returning

the switch to the "auto" position, the circuit breaker's

automatic closing logic closed the breaker.The Wolf Creek licensee modified the EDG breaker control switch located in the control room to enable the operator to reclose the EDG circuit breaker from the control room. This switch was originally

intended only as a means of paralleling

the EDG with the offsite power supply. With the current modification, the switch can be used to reset the anti-pump

logic and allow the automatic

circuit to re-close the breaker. The modification

added a contact that is closed in the "normal" position and open in the "trip" and "pull to lock" positions

of the control switch.When operators

manually trip the EDG circuit breaker from this control switch, the contacts open to interrupt

the close circuit and reset the circuit breaker anti-pump

relay. If the operator wishes to keep the breaker open, he must put the switch in the "pull to lock" position.

Returning

the switch to the "normal" position completes

the automatic

close circuit and the breaker recloses.It should be noted that although the above discussion

has dealt only with EDG output circuit breakers, anti-pump

circuit problems could also apply to other breakers that use automatic

closing logic, such as load-sequencing

breakers and offsite supply breakers to the emergency

buses.The information

herein is being provided as an early notification

of a potentially

significant

matter that is still under consideration

by the NRC staff. If NRC evaluation

so indicates, specific licensee actions may be requested.

No specific action or written response is required by this information

notice.If you have any questions

about this matter, please contact one of the technical contacts listed below or the Regional Administrator

of the appropriate

regional office.Charles E. Rossi, Director Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

Contacts:

James Lazevnick, NRR (301) 492-0814 Carl Schulten, NRR (301) 492-1192 Fred Burrows, NRR (301) 492-0783 Attachment:

List of Recently Issued NRC Information

Notices*SEE PREVIOUS PAGE FOR CONCURRENCE

OFC *OEAB *Tech Ed *SL:OEAB *C:OEAB *D:DEST *C:OGCB NAME CSchulten

BCalure PBaranowsky

WLanning LShao CBerlinger

e l DATE 9/7/88 7/28/88 9/7/88 9/7/88 8/24/88 9/8/88 9/(,f 88 IN 88-September , 1988 contact was reclosed by returning

the switch to the "auto" position.

the circuit breaker's

automatic

closing logic closed the breaker.The Wolf Creek licensee modified the EDG breaker control switch located in the control room to enable the operator to reclose the EDG circuit breaker from the control room. This switch was originally

intended only as a means of paralleling

the EDG with the offsite power supply. With the current modification.

the switch can be used to reset the anti-pump

logic and allow the automatic

circuit to reclose the breaker. The modification

added a contact that is closed in the "normal" position and open in the "trip" and"pull to lock" positions

of the control switch. When operators

manually trip the EDG circuit breaker from this control switch. the contacts open to interrupt

the close circuit and reset the circuit breaker anti-pump

relay.If the operator wishes to keep the breaker open. he must put the switch in the"pull to lock" position.

Returning

the switch to the "normal" position completes

the automatic

close circuit and the breaker recloses.It should be noted that although the above discussion

has dealt only with EDG output circuit breakers.

the anti-pump

circuit problem could also apply to other breakers that use automatic

closing logic, such as load-sequencing

breakers and offsite supply breakers to the emergency

buses.The information

herein is being provided as an early notification

of a potentially

significant

matter that is still under consideration

by the NRC staff. If NRC evaluation

so indicates.

specific licensee actions may be requested.

No specific action or written response is required by this information

notice. If you have any questions

about this matter, please contact any of the technical

contacts listed below or the Regional Administrator

of the appropriate

regional office.Charles E. Rossi, Director Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

Contacts:

James Lazevnick.

NRR (301) 492-0814 Carl Schulten.

NRR (301) 492-1192 Fred Burrows. NRR (301) 492-0783-e --- --:D: -NAME :CSchu Mn are :P aranowsky

WLan n :LShao :CBeri nger :ERossi DATE q 88 /8 :1/88 /88 :18188 /88 OFFICIAL RECORD COPY

IN 88-August .1988 contact was reclosed by returning

the switch to the "auto" position.

the circuit breaker's

automatic

closing logic closed the breaker.The Wolf Creek licensee modified the EDG breaker control switch located in the control room to enable the operator to reclose the EDG circuit breaker from the control room. This switch was originally

intended only as a means of paralleling

the EDG with the offsite power supply. With the current modification.

the switch can be used to reset the anti-pumping

logic and allow the automatic

circuit to reclose the breaker. The modification

added a contact that is closed in the "normal" position and open in the "trip" and"pull to lock" positions

of the control switch. When operators

manually trip the EDG circuit breaker from this control switch, the contacts open to interrupt

the close circuit and reset the circuit breaker anti-pumping

relay.If the operator wishes to keep the breaker open. he must put the switch in the"pull to lock" position.

Returning

the switch to the "normal" position completes

the automatic

close circuit and the breaker recloses.It should be noted that although the above discussion

has dealt only with EDG output circuit breakers, the same problem could also apply to other breakers that use automatic

closing logic, such as load-sequencing

breakers and offsite supply breakers to the emergency

buses.The information

herein is being provided as an early notification

of a potentially

significant

matter that is still under consideration

by the NRC staff. If NRC evaluation

so indicates.

specific licensee actions may be requested.

No specific action or written responses

is required by this information

notice. If you have any questions

about this matter, please contact either the technical

contacts listed below or the Regional Administrator

of the appropriate

regional office.Charles E. Rossi. Director Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

Contact: James Lazevnick.

NRR (301) 492-0814 Carl Schulten.

NRR (301) 492-1192 Fred Burrows. NRR (301) 492-0783 OFC _: T EOGCB :D:DOEA t "4i> -:-8{tjA---:-4og-yF---:---4-----------------

-----------

NAME :CSchulten

B& lure :PB pnowsky :WLanni:LS

CBerlinger

ERossi DATE 1&/ : //88 F./ A1/88 1.V 1.8 8 4f8 8 8 DAT O F:I g/ECORD : / /88COPY OFFICIAL RECORD COPY

NRC INFO NOTICE 88-XX. DIESEL GENERATOR

CIRCUIT BREAKERS FAIL TO AUTOMATICALLY

CLOSE OFC :OEAB :Te h Ed :SL:OEAB :C:OEAb :L:SELB :C:OGCB :D:DUEA NAME :CSchulten

lure :PBaranowsky

WLanning

FRosa :CBerlinger

ERossl DATE : / 88 /88 : I /88 / /88 : / /88 : / /88 OFFICIAL RECORD COPY