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

From kanterella
Jump to navigation Jump to search
(Created page by program invented by StriderTol)
 
(Created page by program invented by StriderTol)
 
(4 intermediate revisions by the same user not shown)
Line 3: Line 3:
| issue date = 09/16/1988
| issue date = 09/16/1988
| title = Disabling of Diesel Generator Output Circuit Breakers by Anti-Pump Circuitry
| title = Disabling of Diesel Generator Output Circuit Breakers by Anti-Pump Circuitry
| author name = Rossi C E
| author name = Rossi C
| author affiliation = NRC/NRR
| author affiliation = NRC/NRR
| addressee name =  
| addressee name =  
Line 13: Line 13:
| document type = NRC Information Notice
| document type = NRC Information Notice
| page count = 8
| page count = 8
| revision = 0
}}
}}
{{#Wiki_filter:IUNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555September 16, 1988NRC INFORMATION NOTICE NO. 88-75: DISABLING OF DIESEL GENERATOR OUTPUTCIRCUIT BREAKERS BY ANTI-PUMP CIRCUITRY
{{#Wiki_filter: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==
==Addressees==
:All holders of operating licenses or construction permits for nuclear powerreactors.
:
  All holders of operating licenses or construction permits for nuclear power
 
reactors.


==Purpose==
==Purpose==
:This information notice is being provided to alert addressees to potentialproblems where the capability to either automatically or manually closediesel generator circuit breakers from the control room may be lost. Itis expected that recipients will review the information for applicabilityto their facilities and consider actions, as appropriate, to avoid similarproblems. However, suggestions contained in this information notice do notconstitute NRC requirements; therefore, no specific action or written responseis required.
:
  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==
==Description of Circumstances==
:On June 5, 1988, operators at Browns Ferry Unit 3 were unable to reclose thediesel generator output breakers to the 4-kV shutdown boards from the controlroom during a loss-of-power/loss-of-coolant-accident (LOP/LOCA) test. Duringthe test, the output breakers connected the diesel generators to their respec-tive 4-kV shutdown boards after the LOP signal was generated; however, thebreakers tripped and remained open after receiving the LOCA signal. Operatorsdiagnosed the output breaker lockout problem using system electrical configu-ration drawings. An operator was sent to the 4-kY shutdown board to manuallytransfer output breaker control power to its alternate source. This momentarilyremoved power, enabling the breaker to close when the power was restored.On October 14, 1987, an operator at Wolf Creek Generating Station manuallytripped the output circuit breaker of the emergency diesel generator (EDG)from the control room. At the time, the EDG was supplying a vital bus. Whenthe 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 controlroom. The vital bus was finally reenergized from the offsite power supply.Through examination of the breaker control schematics the licensee laterfound that the EDG circuit breaker could be closed by cycling the EDG modeswitch at the EDG local control station.880920197 IN 88-75September 16, 1988 Discussion:The anti-pump circuit configuration will protect large breakers from rapidcycling and, under certain circumstances, will prevent breaker closure. AtBrowns Ferry Unit 3, a unique sequence of events, a LOP signal followed within6 seconds by a LOCA signal, led to the discovery of a design deficiency of thiscircuit configuration. Contacts from the undervoltage relay will seal in thebreaker anti-pump relay until the undervoltage condition on the 4-kV boardsclears.The circuit is designed such that following a LOP, the undervoltage conditionmust exist for at least 5 seconds and the diesel. must reach rated speed beforethe diesel generator output breaker will close on the bus. Once the breakerhas closed, the closure spring recharge motor and the breaker anti-pump relaywill be energized. A fully discharged closure spring requires 2 seconds forthe spring to be fully recharged. During this 2 second window the anti-pumpcoil will remain energized via contacts sensing spring position, and if anundervoltage condition exists on the 4-kY bus it will seal in and lock openthe breaker.During the Browns Ferry event, the EDG output breaker closed 5 seconds afterthe LOP signal, the undervoltage condition was eliminated, and the undervoltagerelay began its 5 second cycle to reset from the undervoltage condition. About1.5 seconds 1ater. the. LOCA-signaL-retr-ipped-the-breaker-and-created-another--undervoltage condition on the 4-kV bus. At this point, because the undervoltagerelay had not completed its reset cycle, the undervoltage relay remained in itsundervoltage state. Therefore, the undervoltage relay sealed in the still-energized anti-pump relay because the undervoltage condition occurred beforethe breaker charging spring was fully charged. Thus, the breaker could notbe closed from the control room either manually or automatically until controlpower 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 relayin the breaker trip coil circuitry. This relay will be energized by a LOCAsignal and its contact in the anti-pump coil seal-in path will open after a2-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 closethe 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 thebreaker's internal anti-pump relay energized as long as the logic permissivesare satisfied. The anti-pump relay prevents the circuit breaker from cyclingif attempts are made to hold the breaker closed against a valid trip signal.I',
:
IN 88-75September 16, 1988 When the Wolf Creek operator manually tripped the EDG output breaker, the auto-matic closing logic permissives remained satisfied. Therefore, the anti-pumprelay remained energized, preventing reclosure of the circuit breaker. Cyclingthe EDG mode control switch at the local control station allowed the circuitbreaker to reclose by momentarily interrupting the automatic close signal, there-by resetting the anti-pump logic. When the mode switch contact was reclosed byreturning the switch to the "auto' position, the circuit breaker's automaticclosing logic closed the breaker.The Wolf Creek licensee modified the EDG breaker control switch located in thecontrol room to enable the operator to reclose the EDG circuit breaker from thecontrol room. This switch was originally intended only as a means of parallelingthe EDG with the offsite power supply. With the current modification, the switchcan 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 breakeranti-pump relay. If the operator wishes to keep the breaker open, he must putthe 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 EDGoutput- circuit breakers, anti-pump circuit problems could also apply to otherbreakers that use automatic closing logic, such as load-sequencing breakersand offsite supply breakers to the emergency buses.The information herein is being provided as an early notification of a potentiallysignificant matter that is still under consideration by the NRC staff. If NRCevaluation 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 technicalcontacts listed below or the Regional Administrator of the appropriate regionaloffice.Di rectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: James Lazevnick, NRR(301) 492-0814Carl Schulten, NRR(301) 492-1192Fred Burrows, NRR(301) 492-0783
  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
 
NRCINFORMATION NOTICES
 
Notice No.    Subject                        Issuance  Issued to
 
88-74          Potentially Inadequate        9/14/88  All holders of OLs
 
Perfornance of ECCSin                    or CPs for Wand
 
PWRs During Recirculation                8&W-designei nuclear
 
Operation Following a LOCA              power reactors.
 
88-73          Direction-Dependent Leak      9/8/88    All holders of 0Ls
 
Characteristics of                      or CPs for nuclear
 
Containment Purge Valves                power reactors.
 
88-72          Inadequacies in the Design    9/2/88  All holders of OLs
 
of dc Motor-Operated Valves            or CPs for nuclear
 
power reactors.
 
88-71          Possible Environmental        9/1/88  All holders of OLs
 
Effect of the Reentry                  or CPs for nuclear
 
of COSMOS  1900 and                    power reactors, fuel
 
Request for Collection                  cycle licensees, of Licensee Radioactivity              and Priority I
 
Measurements Attributed                  material licensees.
 
to That Event
 
88-70          Check Valve Inservice          8/29/88  All holders of OLs
 
Testing Program                          or CPs for nuclear
 
Deficiencies                            power reactors.
 
88-69          Movable Contact Finger        8/19/88  All holders of OLs
 
Binding in HFA Relays                    or CPs for nuclear
 
Manufactured by General                  power reactors.
 
Electric (GE)
                          88-48,        Licensee Report of Defective 8/24/88    All holders of OLs
 
Supplement I  Refurbished Valves                      or CPs for nuclear
 
power reactors.
 
88-68          Setpoint Testing of Pres-      8/22/88  All holders of OLs
 
surizer Safety Valves with              or CPs for nuclear
 
Filled Loop Seals Using                  power reactors.
 
Hydraulic Assist Devices
 
_
                          88P67-      -P-F    Zfiiairy Fiedeaer Pump  8/Z2j88  All holders of OLs
 
Turbine Overspeed Trip                  or CPs for nuclear
 
Failure                                  power reactors.
 
OL
 
* Operating License
 
CP* Construction Permit
 
UNITED STATES                                                                                  FIRST CLASS MAIL
 
NUCLEAR REGULATORY COMMISSION                                                                            POSTAGE & FEES PAID
 
USNRC
 
WASHINGTON, D.C. 20555 PERMIT No. 0-57 OFFICIAL BUSINESS
 
PENALTY FOR PRIVATE USE, $300
 
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            Ed *SL:OEAB
 
*Tech      *C:OEAB *D:DEST  *C:OGCB
 
NAME CSchulten BCalure  PBaranowsky  WLanning LShao    CBerlinger    e    l
 
9/(,f 88 DATE 9/7/88    7/28/88 9/7/88        9/7/88  8/24/88  9/8/88
 
IN 88- September , 1988 the
 
contact was reclosed by returning the switch to the "auto" position.
 
circuit breaker's automatic closing logic        closed    the  breaker.
 
in the
 
The Wolf Creek licensee modified the EDG breaker control switch located from
 
control room to enable the operator to      reclose    the  EDG  circuit    breaker
 
of
 
the control room. This switch was originally intended only as a means
 
paralleling the EDG with the offsite      power    supply.    With  the  current
 
allow
 
modification. the switch can be used to reset the anti-pump logic and
 
breaker.      The  modification      added  a
 
the automatic circuit to reclose the                                                    and
 
contact that is closed in the "normal"      position    and  open  in  the  "trip"
                                                        switch.    When  operators    manually  trip
 
"pull to lock" positions of the control                                            to
 
the EDG circuit breaker from this      control    switch.    the  contacts    open
 
interrupt the close circuit and reset the circuit breaker anti-pump                relay.
 
the  breaker    open.  he  must  put  the  switch  in the
 
If the operator wishes to keep
 
"pull to lock" position. Returning the switch to the "normal" position
 
completes the automatic close circuit and the breaker recloses.
 
EDG
 
It should be noted that although the above discussion has dealt only withto other
 
circuit    problem    could  also  apply
 
output circuit breakers. the anti-pump                                            breakers and
 
breakers that use automatic closing logic, such as load-sequencing
 
offsite supply breakers to the emergency buses.
 
a
 
The information herein is being provided as an early notification byof the NRC
 
potentially significant    matter that  is  still    under  consideration
 
be
 
staff. If NRC evaluation so indicates. specific licensee actions may
 
requested.
 
No specific action or written response is required by this informationany of the
 
notice. If you have any questions about this matter, please contact appropriate
 
technical contacts listed below or the Regional Administrator of the
 
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
 
The Wolf Creek licensee modified the EDG breaker control switch located in
 
breaker  from
 
control room to enable the operator to reclose the EDG circuit
 
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 aand
 
contact that is closed in the "normal" position and open in the "trip"          trip
 
"pull to lock" positions of the control switch. When operators manually
 
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.
 
EDG
 
It should be noted that although the above discussion has dealt only with
 
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              the
 
notice. If you have any questions about this matter, please contact either
 
technical contacts listed below or the Regional Administrator      of  the  appropriate
 
regional office.


===Attachment:===
Charles E. Rossi. Director
List of Recently Issued NRC Information Notices Att"aantIN 88-75September 16, 1988Page I of ILIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESNotice No. Subject Issuance88-74 Potentially Inadequate 9/14/88Perfornance of ECCS inPWRs During RecirculationOperation Following a LOCA88-73 Direction-Dependent Leak 9/8/88Characteristics ofContainment Purge Valves88-72 Inadequacies in the Design 9/2/88of dc Motor-Operated Valves88-71 Possible Environmental 9/1/88Effect of the Reentryof COSMOS 1900 andRequest for Collectionof Licensee RadioactivityMeasurements Attributedto That Event88-70 Check Valve Inservice 8/29/88Testing ProgramDeficiencies88-69 Movable Contact Finger 8/19/88Binding in HFA RelaysManufactured by GeneralElectric (GE)88-48, Licensee Report of Defective 8/24/88Supplement I Refurbished Valves88-68 Setpoint Testing of Pres- 8/22/88surizer Safety Valves withFilled Loop Seals UsingHydraulic Assist Devices88P67- -P-F Zfiiairy Fiedeaer Pump 8/Z2j88Turbine Overspeed TripFailureOL
* Operating LicenseCP
* Construction PermitIssued toAll holders of OLsor CPs for W and8&W-designei nuclearpower reactors.All holders of 0Lsor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors, fuelcycle licensees,and Priority Imaterial licensees.All holders of OLsor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors._UNITED STATESNUCLEAR REGULATORY COMMISSIONWASHINGTON, D.C. 20555OFFICIAL BUSINESSPENALTY FOR PRIVATE USE, $300FIRST CLASS MAILPOSTAGE & FEES PAIDUSNRCPERMIT No. 0-57 IN 88-75September 16, 1988 When the Wolf Creek operator manually tripped the EDG output breaker, the auto-matic closing logic permissives remained satisfied. Therefore, the anti-pumprelay remained energized, preventing reclosure of the circuit breaker. Cyclingthe EDG mode control switch at the local control station allowed the circuitbreaker to reclose by momentarily interrupting the automatic close signal, there-by resetting the anti-pump logic. When the mode switch contact was reclosed byreturning the switch to the "auto" position, the circuit breaker's automaticclosing logic closed the breaker.The Wolf Creek licensee modified the EDG breaker control switch located in thecontrol room to enable the operator to reclose the EDG circuit breaker from thecontrol room. This switch was originally intended only as a means of parallelingthe EDG with the offsite power supply. With the current modification, the switchcan 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 breakeranti-pump relay. If the operator wishes to keep the breaker open, he must putthe 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 EDGoutput circuit breakers, anti-pump circuit problems could also apply to otherbreakers that use automatic closing logic, such as load-sequencing breakersand offsite supply breakers to the emergency buses.The information herein is being provided as an early notification of a potentiallysignificant matter that is still under consideration by the NRC staff. If NRCevaluation 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 technicalcontacts listed below or the Regional Administrator of the appropriate regionaloffice.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: James Lazevnick, NRR(301) 492-0814Carl Schulten, NRR(301) 492-1192Fred Burrows, NRR(301) 492-0783


===Attachment:===
Division of Operational Events Assessment
List of Recently Issued NRC Information Notices*SEE PREVIOUS PAGE FOR CONCURRENCEOFC *OEAB *Tech Ed *SL:OEAB *C:OEAB *D:DEST *C:OGCBNAME CSchulten BCalure PBaranowsky WLanning LShao CBerlinger e lDATE 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. thecircuit breaker's automatic closing logic closed the breaker.The Wolf Creek licensee modified the EDG breaker control switch located in thecontrol room to enable the operator to reclose the EDG circuit breaker fromthe control room. This switch was originally intended only as a means ofparalleling the EDG with the offsite power supply. With the currentmodification. the switch can be used to reset the anti-pump logic and allowthe automatic circuit to reclose the breaker. The modification added acontact that is closed in the "normal" position and open in the "trip" and"pull to lock" positions of the control switch. When operators manually tripthe EDG circuit breaker from this control switch. the contacts open tointerrupt 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" positioncompletes the automatic close circuit and the breaker recloses.It should be noted that although the above discussion has dealt only with EDGoutput circuit breakers. the anti-pump circuit problem could also apply to otherbreakers that use automatic closing logic, such as load-sequencing breakers andoffsite supply breakers to the emergency buses.The information herein is being provided as an early notification of apotentially significant matter that is still under consideration by the NRCstaff. If NRC evaluation so indicates. specific licensee actions may berequested.No specific action or written response is required by this informationnotice. If you have any questions about this matter, please contact any of thetechnical contacts listed below or the Regional Administrator of the appropriateregional office.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: James Lazevnick. NRR(301) 492-0814Carl Schulten. NRR(301) 492-1192Fred Burrows. NRR(301) 492-0783-e --- --:D: -NAME :CSchu Mn are :P aranowsky :WLan n :LShao :CBeri nger :ERossiDATE q 88 /8 :1/88 /88 :18188 /88OFFICIAL RECORD COPY IN 88-August .1988 contact was reclosed by returning the switch to the "auto" position. thecircuit breaker's automatic closing logic closed the breaker.The Wolf Creek licensee modified the EDG breaker control switch located in thecontrol room to enable the operator to reclose the EDG circuit breaker fromthe control room. This switch was originally intended only as a means ofparalleling the EDG with the offsite power supply. With the currentmodification. the switch can be used to reset the anti-pumping logic and allowthe automatic circuit to reclose the breaker. The modification added acontact that is closed in the "normal" position and open in the "trip" and"pull to lock" positions of the control switch. When operators manually tripthe EDG circuit breaker from this control switch, the contacts open tointerrupt 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" positioncompletes the automatic close circuit and the breaker recloses.It should be noted that although the above discussion has dealt only with EDGoutput circuit breakers, the same problem could also apply to other breakersthat use automatic closing logic, such as load-sequencing breakers and offsitesupply breakers to the emergency buses.The information herein is being provided as an early notification of apotentially significant matter that is still under consideration by the NRCstaff. If NRC evaluation so indicates. specific licensee actions may berequested.No specific action or written responses is required by this informationnotice. If you have any questions about this matter, please contact either thetechnical contacts listed below or the Regional Administrator of the appropriateregional office.Charles E. Rossi. DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor Regulation
 
Office of Nuclear Reactor Regulation


===Technical Contact:===
===Technical Contact:===
James Lazevnick. NRR(301) 492-0814Carl Schulten. NRR(301) 492-1192Fred Burrows. NRR(301) 492-0783OFC _: T EOGCB :D:DOEAt "4i> -:-8{tjA---:-4og-yF---:---4----------------- :-----------NAME :CSchulten :B& lure :PB pnowsky :WLanni:LS :CBerlinger :ERossiDATE 1&/ : //88 F./ A1/88 1.V1.88 4f8 8 8DAT O F:I g/ECORD : / /88COPYOFFICIAL RECORD COPY NRC INFO NOTICE 88-XX. DIESEL GENERATOR CIRCUIT BREAKERS FAIL TO AUTOMATICALLYCLOSEOFC :OEAB :Te h Ed :SL:OEAB :C:OEAb :L:SELB :C:OGCB :D:DUEANAME :CSchulten lure :PBaranowsky :WLanning :FRosa :CBerlinger :ERosslDATE : / 88 /88 : I /88 / /88 : / /88 : / /88OFFICIAL RECORD COPY}}
 
===James Lazevnick. NRR===
                                (301) 492-0814 Carl Schulten. NRR
 
(301) 492-1192 Fred Burrows. NRR
 
(301) 492-0783 T       EOGCB                                                           :D:DOEA
 
OFC  _:
                            t  -:-8{tjA---:-4og-yF---:---4-----------------:-----------
                                "4i>
                                                                                            :ERossi
 
NAME :CSchulten   :B& lure       :PB   pnowsky :WLanni:LS                 :CBerlinger
 
:   //88         F./ A1/88       .1.V8 8    4f8               8/88COPY        8 DATE1&/O F:I                                 1                g/ECORD : /
DAT
 
OFFICIAL RECORD COPY
 
TO AUTOMATICALLY
 
NRC INFO NOTICE 88-XX. DIESEL GENERATOR CIRCUIT BREAKERS FAIL
 
CLOSE
 
:SL:OEAB     :C:OEAb     :L:SELB     :C:OGCB     :D:DUEA
 
OFC  :OEAB        :Te h Ed
 
lure     :PBaranowsky :WLanning   :FRosa       :CBerlinger :ERossl
 
NAME :CSchulten
 
/88   : I   /88       / /88   : /   /88   : /   /88 DATE :    / 88 OFFICIAL RECORD COPY}}


{{Information notice-Nav}}
{{Information notice-Nav}}

Latest revision as of 03:52, 24 November 2019

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
Office of Nuclear Reactor Regulation
To:
References
IN-88-075, NUDOCS 8809120197
Download: ML031150110 (8)
v • d • e


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

NRCINFORMATION NOTICES

Notice No. Subject Issuance Issued to

88-74 Potentially Inadequate 9/14/88 All holders of OLs

Perfornance of ECCSin or CPs for Wand

PWRs During Recirculation 8&W-designei nuclear

Operation Following a LOCA power reactors.

88-73 Direction-Dependent Leak 9/8/88 All holders of 0Ls

Characteristics of or CPs for nuclear

Containment Purge Valves power reactors.

88-72 Inadequacies in the Design 9/2/88 All holders of OLs

of dc Motor-Operated Valves or CPs for nuclear

power reactors.

88-71 Possible Environmental 9/1/88 All holders of OLs

Effect of the Reentry or CPs for nuclear

of COSMOS 1900 and power reactors, fuel

Request for Collection cycle licensees, of Licensee Radioactivity and Priority I

Measurements Attributed material licensees.

to That Event

88-70 Check Valve Inservice 8/29/88 All holders of OLs

Testing Program or CPs for nuclear

Deficiencies power reactors.

88-69 Movable Contact Finger 8/19/88 All holders of OLs

Binding in HFA Relays or CPs for nuclear

Manufactured by General power reactors.

Electric (GE)

88-48, Licensee Report of Defective 8/24/88 All holders of OLs

Supplement I Refurbished Valves or CPs for nuclear

power reactors.

88-68 Setpoint Testing of Pres- 8/22/88 All holders of OLs

surizer Safety Valves with or CPs for nuclear

Filled Loop Seals Using power reactors.

Hydraulic Assist Devices

_

88P67- -P-F Zfiiairy Fiedeaer Pump 8/Z2j88 All holders of OLs

Turbine Overspeed Trip or CPs for nuclear

Failure power reactors.

OL

  • Operating License

CP* Construction Permit

UNITED STATES FIRST CLASS MAIL

NUCLEAR REGULATORY COMMISSION POSTAGE & FEES PAID

USNRC

WASHINGTON, D.C. 20555 PERMIT No. 0-57 OFFICIAL BUSINESS

PENALTY FOR PRIVATE USE, $300

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 Ed *SL:OEAB

  • Tech *C:OEAB *D:DEST *C:OGCB

NAME CSchulten BCalure PBaranowsky WLanning LShao CBerlinger e l

9/(,f 88 DATE 9/7/88 7/28/88 9/7/88 9/7/88 8/24/88 9/8/88

IN 88- September , 1988 the

contact was reclosed by returning the switch to the "auto" position.

circuit breaker's automatic closing logic closed the breaker.

in the

The Wolf Creek licensee modified the EDG breaker control switch located from

control room to enable the operator to reclose the EDG circuit breaker

of

the control room. This switch was originally intended only as a means

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

allow

modification. the switch can be used to reset the anti-pump logic and

breaker. The modification added a

the automatic circuit to reclose the and

contact that is closed in the "normal" position and open in the "trip"

switch. When operators manually trip

"pull to lock" positions of the control to

the EDG circuit breaker from this control switch. the contacts open

interrupt the close circuit and reset the circuit breaker anti-pump relay.

the breaker open. he must put the switch in the

If the operator wishes to keep

"pull to lock" position. Returning the switch to the "normal" position

completes the automatic close circuit and the breaker recloses.

EDG

It should be noted that although the above discussion has dealt only withto other

circuit problem could also apply

output circuit breakers. the anti-pump breakers and

breakers that use automatic closing logic, such as load-sequencing

offsite supply breakers to the emergency buses.

a

The information herein is being provided as an early notification byof the NRC

potentially significant matter that is still under consideration

be

staff. If NRC evaluation so indicates. specific licensee actions may

requested.

No specific action or written response is required by this informationany of the

notice. If you have any questions about this matter, please contact appropriate

technical contacts listed below or the Regional Administrator of the

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

The Wolf Creek licensee modified the EDG breaker control switch located in

breaker from

control room to enable the operator to reclose the EDG circuit

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 aand

contact that is closed in the "normal" position and open in the "trip" trip

"pull to lock" positions of the control switch. When operators manually

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.

EDG

It should be noted that although the above discussion has dealt only with

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 the

notice. If you have any questions about this matter, please contact either

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 T EOGCB :D:DOEA

OFC _:

t -:-8{tjA---:-4og-yF---:---4-----------------:-----------

"4i>

ERossi

NAME :CSchulten :B& lure :PB pnowsky :WLanni:LS :CBerlinger

//88 F./ A1/88 .1.V8 8 4f8 8/88COPY 8 DATE1&/O F:I 1 g/ECORD : /

DAT

OFFICIAL RECORD COPY

TO AUTOMATICALLY

NRC INFO NOTICE 88-XX. DIESEL GENERATOR CIRCUIT BREAKERS FAIL

CLOSE

SL:OEAB :C:OEAb :L:SELB :C:OGCB :D:DUEA

OFC :OEAB :Te h Ed

lure :PBaranowsky :WLanning :FRosa :CBerlinger :ERossl

NAME :CSchulten

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


Retrieved from "https://kanterella.com/w/index.php?title=Information_Notice_1988-75,_Disabling_of_Diesel_Generator_Output_Circuit_Breakers_by_Anti-Pump_Circuitry&oldid=2200754"