Information Notice 1992-51, Misapplication and Inadequate Testing of Molded-Case Circuit Breakers: Difference between revisions

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{{#Wiki_filter:JoS / KUUNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555July 9, 1992NRC INFORMATION NOTICE 92-51: MISAPPLICATION AND INADEQUATE TESTINGOF MOLDED-CASE CIRCUIT BREAKERS
{{#Wiki_filter:JoS / KU UNITED STATES NUCLEAR REGULATORY
 
COMMISSION
 
===OFFICE OF NUCLEAR REACTOR REGULATION===
WASHINGTON, D.C. 20555 July 9, 1992 NRC INFORMATION
 
NOTICE 92-51: MISAPPLICATION
 
AND INADEQUATE
 
TESTING OF MOLDED-CASE
 
CIRCUIT BREAKERS


==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==
TheU.S. Nuclear Regulatory Commission (NRC) is issuing this informationnotice to alert addressees to problems that were recently observed concerningthe application and testing of molded-case circuit breakers (MCCBs). It isexpected that recipients will review the information for applicability totheir facilities and consider actions, as appropriate, to avoid similarproblems. However, suggestions contained in this information notice are notNRC requirements; therefore, no specific action or written response isrequired.
TheU.S. Nuclear Regulatory
 
Commission (NRC) is issuing this information
 
notice to alert addressees
 
to problems that were recently observed concerning
 
the application
 
and testing of molded-case
 
circuit breakers (MCCBs). 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 are not NRC requirements;  
therefore, no specific action or written response is required.Description
 
of Circumstances
 
During research and inspection
 
activities, the NRC staff has found that licensees, when determining
 
the MCCB parameters
 
for motor loads, occasionally
 
underestimate
 
or neglect to consider the inrush transient (starting)
current (ITC) occurring
 
during the first few cycles after a motor is started. Often only the locked rotor current (LRC) is considered
 
in selecting
 
the appropriate- MCCB.If no special starting methodology
 
is used to specifically
 
limit the ITC, the magnitude
 
of the ITC can be as much as approximately
 
three times the LRC.Also, depending
 
on the electrical
 
characteristics
 
of the power supply and the impedance
 
of the motor when started, the ITC can increase to as much as approximately
 
six times the value of the LRC. A current of this magnitude
 
is greater than the maximum instantaneous
 
trip setting for circuit protection
 
recommended
 
by the National Electric Code (NEC). Therefore, the NEC recommended
 
level of protection
 
may be insufficient
 
to prevent an unwanted trip. Proper application
 
of MCCBs depends strongly upon the use of accurate design assumptions.
 
Another application
 
problem involves the use of MCCBs equipped with both thermal overload trip elements and instantaneous
 
magnetic trip elements.
 
A newly purchased
 
replacement
 
Westinghouse
 
===Type HFB3125 ambient compensating===
MCCB tripped when a hydrogen skimmer fan motor at the Catawba Nuclear Station 7 9207020233
\J 1-IN 92-51 July 9, 1992 was started during testing after installation.
 
Duke Power Company personnel did not expect the MCCB to trip since the peak value of the ITC for the fan motor was thought to be well below the instantaneous
 
trip band of that MCCB (NRC Inspection
 
Report 99900404/90-01).
 
A similar Westinghouse
 
MCCB used as a turbine room sump pump breaker tripped in a similar manner at the Donald C. Cook Nuclear Power Plant. (NRC Inspection
 
Report 99900404/90-21).
 
Westinghouse
 
determined
 
that most of its thermal-magnetic
 
MCCBs with the nonadjustable
 
instantaneous
 
magnetic trip function could trip inadvertently.
 
Westinghouse
 
attributed
 
this behavior to interaction
 
between the thermal overload trip function and the instantaneous
 
magnetic trip function under overload conditions.
 
Under nonfault conditions, these functions
 
may interact when the circuit current causes the thermal trip element to deflect until it presses on the MCCB's tripper bar at the same time that the instantaneous
 
magnetic armature is vibrating
 
against the tripper bar. This interaction
 
causes the MCCB to trip.Westinghouse
 
notified nuclear licensees
 
of this problem and recommended
 
that they test these MCCBs in their intended circuits before releasing
 
them for plant operation.
 
Westinghouse
 
also stated this recommendation
 
on certificates
 
of conformance
 
provided with its dedicated
 
MCCBs sold as safety-related
 
items.Potential
 
interactions
 
between thermal overload and instantaneous
 
trip functions
 
can be avoided by using a special class of MCCBs that are designed specifically
 
for motor loads. These MCCBs include only instantaneous
 
magnetic trip functions
 
for protecting
 
against faults or short circuits.
 
The trip setpoints
 
are normally adjustable
 
and more accurate than those in thermal-magnetic MCCBs. These MCCBs, commonly referred to by the Westinghouse
 
term"motor circuit protectors," are intended for use in combination
 
with motor contactors
 
or starters.
 
Thermal overload relays contained
 
in the contactors
 
or starters provide the coordinated
 
protection
 
against overloads
 
and fault currents which are below the magnitude
 
necessary
 
to actuate an instantaneous
 
trip of the MCCB.Instances
 
of premature
 
tripping have occurred with MCCBs manufactured
 
by ITE-Siemens Company. The Carolina Power and Light Company, licensee for the Shearon Harris Nuclear Power Plant, found that some of the 480 volt MCCBs manufactured
 
by ITE-Siemens, and purchased
 
as commercial-grade, tripped prematurely
 
when tested (NRC Inspection
 
Report 99901177/90-01).
 
The licensee had purchased
 
these MCCBs as replacements
 
for some older 600 volt ITE-Siemens
 
MCCBs. The ITE-Siemens
 
Company tested the 480 volt MCCBs and found that these trips were initiated
 
by the MCCBs' instantaneous
 
magnetic trip function, when induction
 
motor loads were started. The manufacturer
 
tested the older 600 volt MCCBs and found no premature
 
trips. Rather, the older 600 volt MCCBs tripped at currents significantly
 
above the levels at which an instantaneous
 
trip should have occurred.
 
i X -X IN 92-51 July 9, 1992 The licensee's
 
testing of the 480 volt MCCBs was judicious.
 
ITE-Siemens
 
stated that the instantaneous
 
trip setpoints
 
of commercial
 
grade MCCBs-with
 
nonadjustable
 
magnetic trips are not normally-verified
 
at the factory.However, ITE-Siemens
 
and possibly other manufacturers
 
of MCCBs will, upon request, verify that the instantaneous
 
magnetic trip points of their commercial
 
grade MCCBs with nonadjustable
 
magnetic trips supplied to nuclear utilities
 
fall within the appropriate
 
design band. Nevertheless, field testing of other MCCBs may be needed to verify that their magnetic trip points occur within the-design
 
band (but not below the band) because other manufacturers
 
may not routinely
 
provide this verification
 
for commercial
 
grade MCCBs. For this type of MCCB, most manufacturers
 
check only that the MCCB will trip instantaneously, without determining
 
the current level at which the trip occurs.Discussion
 
An MCCB can render safety-related
 
equipment
 
inoperable
 
if it trips prematurely.
 
Premature
 
trips can result if the incorrect
 
MCCB is selected (and/or incorrectly
 
adjusted)
as a result of inadequate
 
analysis of the load circuit including
 
dynamic analysis of expected transients
 
when determining
 
ratings, settings and coordination
 
requirements.
 
Premature
 
trips can also-occur with properly applied and set MCCBs that are operating
 
out of tolerance when incorrect
 
bench testing methods and/or inadequate
 
post-installation
 
testing fail to detect the out of tolerance
 
performance.
 
Acceptable
 
testing methods and specifications
 
are provided in some MCCB manufacturers'
technical
 
publications.
 
===Industry and professional===
organizations
 
also provide guidance on MCCB testing methods, including
 
generic acceptance
 
criteria, in documents
 
such as the National Electrical
 
Manufacturers
 
Association (NEMA) Standard AB4-1991, "Guidelines
 
for the Inspection
 
and Preventive
 
Maintenance
 
of Molded Case Circuit Breakers Used in Commercial
 
and Industrial
 
Applications." It should be noted that the application
 
of generic field test tolerances
 
to the instantaneous
 
trip band on manufacturers'
time-current
 
characteristic
 
curves may not always ensure that the MCCBs meet plant-specific
 
breaker coordination, circuit protection
 
or technical
 
specification
 
requirements.
 
Testing of properly applied and set MCCBs in accordance
 
with industry recommended
 
practices
 
should provide reasonable
 
assurance
 
that the MCCBs'instantaneous
 
trip performance
 
is acceptable
 
for safety-related
 
applications.
 
IN 92-51 July 9, 1992 This information
 
notice requires no specific action or written response.
 
If you have any questions


==Description of Circumstances==
about the information
During research and inspection activities, the NRC staff has found thatlicensees, when determining the MCCB parameters for motor loads, occasionallyunderestimate or neglect to consider the inrush transient (starting) current(ITC) occurring during the first few cycles after a motor is started. Oftenonly the locked rotor current (LRC) is considered in selecting the appropriate-MCCB.If no special starting methodology is used to specifically limit the ITC, themagnitude of the ITC can be as much as approximately three times the LRC.Also, depending on the electrical characteristics of the power supply and theimpedance of the motor when started, the ITC can increase to as much asapproximately six times the value of the LRC. A current of this magnitude isgreater than the maximum instantaneous trip setting for circuit protectionrecommended by the National Electric Code (NEC). Therefore, the NECrecommended level of protection may be insufficient to prevent an unwantedtrip. Proper application of MCCBs depends strongly upon the use of accuratedesign assumptions.Another application problem involves the use of MCCBs equipped with boththermal overload trip elements and instantaneous magnetic trip elements. Anewly purchased replacement Westinghouse Type HFB3125 ambient compensatingMCCB tripped when a hydrogen skimmer fan motor at the Catawba Nuclear Station7 9207020233
\J 1-IN 92-51July 9, 1992 was started during testing after installation. Duke Power Company personneldid not expect the MCCB to trip since the peak value of the ITC for the fanmotor was thought to be well below the instantaneous trip band of that MCCB(NRC Inspection Report 99900404/90-01). A similar Westinghouse MCCB usedas a turbine room sump pump breaker tripped in a similar manner at theDonald C. Cook Nuclear Power Plant. (NRC Inspection Report 99900404/90-21).Westinghouse determined that most of its thermal-magnetic MCCBs with thenonadjustable instantaneous magnetic trip function could trip inadvertently.Westinghouse attributed this behavior to interaction between the thermaloverload trip function and the instantaneous magnetic trip function underoverload conditions. Under nonfault conditions, these functions may interactwhen the circuit current causes the thermal trip element to deflect until itpresses on the MCCB's tripper bar at the same time that the instantaneousmagnetic armature is vibrating against the tripper bar. This interactioncauses the MCCB to trip.Westinghouse notified nuclear licensees of this problem and recommended thatthey test these MCCBs in their intended circuits before releasing them forplant operation. Westinghouse also stated this recommendation on certificatesof conformance provided with its dedicated MCCBs sold as safety-related items.Potential interactions between thermal overload and instantaneous tripfunctions can be avoided by using a special class of MCCBs that are designedspecifically for motor loads. These MCCBs include only instantaneous magnetictrip functions for protecting against faults or short circuits. The tripsetpoints are normally adjustable and more accurate than those in thermal-magnetic MCCBs. These MCCBs, commonly referred to by the Westinghouse term"motor circuit protectors," are intended for use in combination with motorcontactors or starters. Thermal overload relays contained in the contactorsor starters provide the coordinated protection against overloads and faultcurrents which are below the magnitude necessary to actuate an instantaneoustrip of the MCCB.Instances of premature tripping have occurred with MCCBs manufactured by ITE-Siemens Company. The Carolina Power and Light Company, licensee for theShearon Harris Nuclear Power Plant, found that some of the 480 volt MCCBsmanufactured by ITE-Siemens, and purchased as commercial-grade, trippedprematurely when tested (NRC Inspection Report 99901177/90-01). The licenseehad purchased these MCCBs as replacements for some older 600 volt ITE-SiemensMCCBs. The ITE-Siemens Company tested the 480 volt MCCBs and found that thesetrips were initiated by the MCCBs' instantaneous magnetic trip function, wheninduction motor loads were started. The manufacturer tested the older 600volt MCCBs and found no premature trips. Rather, the older 600 volt MCCBstripped at currents significantly above the levels at which an instantaneoustrip should have occurred.


i X -XIN 92-51July 9, 1992 The licensee's testing of the 480 volt MCCBs was judicious. ITE-Siemensstated that the instantaneous trip setpoints of commercial grade MCCBs-withnonadjustable magnetic trips are not normally-verified at the factory.However, ITE-Siemens and possibly other manufacturers of MCCBs will, uponrequest, verify that the instantaneous magnetic trip points of theircommercial grade MCCBs with nonadjustable magnetic trips supplied to nuclearutilities fall within the appropriate design band. Nevertheless, fieldtesting of other MCCBs may be needed to verify that their magnetic trip pointsoccur within the-design band (but not below the band) because othermanufacturers may not routinely provide this verification for commercial gradeMCCBs. For this type of MCCB, most manufacturers check only that the MCCBwill trip instantaneously, without determining the current level at which thetrip occurs.DiscussionAn MCCB can render safety-related equipment inoperable if it tripsprematurely. Premature trips can result if the incorrect MCCB is selected(and/or incorrectly adjusted) as a result of inadequate analysis of the loadcircuit including dynamic analysis of expected transients when determiningratings, settings and coordination requirements. Premature trips can also-occur with properly applied and set MCCBs that are operating out of tolerancewhen incorrect bench testing methods and/or inadequate post-installationtesting fail to detect the out of tolerance performance.Acceptable testing methods and specifications are provided in some MCCBmanufacturers' technical publications. Industry and professionalorganizations also provide guidance on MCCB testing methods, including genericacceptance criteria, in documents such as the National ElectricalManufacturers Association (NEMA) Standard AB4-1991, "Guidelines for theInspection and Preventive Maintenance of Molded Case Circuit Breakers Used inCommercial and Industrial Applications." It should be noted that theapplication of generic field test tolerances to the instantaneous trip band onmanufacturers' time-current characteristic curves may not always ensure thatthe MCCBs meet plant-specific breaker coordination, circuit protection ortechnical specification requirements.Testing of properly applied and set MCCBs in accordance with industryrecommended practices should provide reasonable assurance that the MCCBs'instantaneous trip performance is acceptable for safety-related applications.
in this notice, please contact one of the technical


IN 92-51July 9, 1992 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.ssi,D ide orDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical contacts: Satish K. Aggarwal, RES(301) 492-3829Stephen D. Alexander, NRR(301) 504-2995Nick Fields, NRR(301) 504-1173Attachment:List of Recently Issued NRC Information Notices
contacts listed below or the appropriate


.-1<-'AttachmentIN 92-51July 9, 1992 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to92-5092-4992-4892-4792-4692-4592-4492-4392-42Cracking of Valves inthe Condensate ReturnLines of A BWR Emer-gency Condenser SystemRecent Loss or SevereDegradation of ServiceWater SystemsFailure of Exide Batteries
Office of Nuclear Reactor Regulation (NRR) project manager.ssi,D ide or Division of Operational
 
===Events Assessment===
Office of Nuclear Reactor Regulation
 
Technical
 
contacts:
Satish K. Aggarwal, RES (301) 492-3829 Stephen D. Alexander, NRR (301) 504-2995 Nick Fields, NRR (301) 504-1173 Attachment:
List of Recently Issued NRC Information
 
Notices
 
.-1<-'Attachment
 
IN 92-51 July 9, 1992 LIST OF RECENTLY ISSUED NRC INFORMATION
 
NOTICES Information
 
Date of Notice No. Subject Issuance Issued to 92-50 92-49 92-48 92-47 92-46 92-45 92-44 92-43 92-42 Cracking of Valves in the Condensate
 
Return Lines of A BWR Emer-gency Condenser
 
System Recent Loss or Severe Degradation
 
of Service Water Systems Failure of Exide Batteries


==Intent==
==Intent==
ional Bypassingof Automatic Actuationof Plant ProtectiveFeaturesThermo-Lag Fire BarrierMaterial Special ReviewTeam Final Report Findings,Current Fire EnduranceTests, and Ampacity Cal-culation ErrorsIncorrect Relay Used inEmergency Diesel GeneratorOutput Breaker ControlCircuitryProblems with Westing-house DS-206 and DSL-206Type Circuit BreakersDefective Molded Phen-olic Armature CarriersFound on Elmwood Con-tactorsFraudulent Bolts inSeismically DesignedWalls07/02/9207/02/9207/02/9206/29/9206/23/9206/22/9206/18/9206/09/9206/01/92All holdersfor BWRs.of OLs or CPsAll holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.OL = Operating LicenseCP = Construction Permit
ional
 
Bypassing of Automatic
 
===Actuation of Plant Protective===
Features Thermo-Lag
 
Fire Barrier Material Special Review Team Final Report Findings, Current Fire Endurance Tests, and Ampacity Cal-culation Errors Incorrect
 
Relay Used in Emergency
 
Diesel Generator Output Breaker Control Circuitry Problems with Westing-house DS-206 and DSL-206 Type Circuit Breakers Defective
 
Molded Phen-olic Armature Carriers Found on Elmwood Con-tactors Fraudulent
 
Bolts in Seismically
 
Designed Walls 07/02/92 07/02/92 07/02/92 06/29/92 06/23/92 06/22/92 06/18/92 06/09/92 06/01/92 All holders for BWRs.of OLs or CPs 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.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.OL = Operating
 
License CP = Construction
 
Permit
 
IN 92-51 July 9, 1992 This information
 
notice requires no specific action or written response.
 
If you have any questions
 
about the information
 
in this notice, please contact one of the technical
 
contacts listed below or the appropriate
 
Office of Nuclear Reactor Regulation (NRR) project manager.Original Signed by Charles E. Rossi Charles E. Rossi, Director Division of Operational
 
===Events Assessment===
Office of Nuclear Reactor Regulation
 
Technical
 
contacts: Satish K. Aggarwal, RES (301) 492-3829 Stephen D. Alexander, NRR (301) 504-2995 Nick Fields, NRR (301) 504-1173 Attachment:
List of Recently Issued NRC Information
 
Notices Brian K. Grimes, Director, Division of Reactor Inspection
 
and Safeguards
 
and Ashok C. Thadani, Director, Division of Systems Technology
 
concurred
 
in a previous version of this information
 
notice. Notice was significantly
 
revised to remove "regulatory
 
guide" portions of original draft after above concurrences
 
were obtained.
 
I determined
 
it was unnecessary
 
to have re-concurrence
 
at the Division Director level. C. E. Rossi*SEE PREVIOUS CONCURRENCE
 
OEAB:DOEA:NRR
 
NFields*05/21/92 EMEB:DE:RES
 
SKAggarwal*
06/08/92 SELB:NRR ASGill*06/29/92 SC/OEAB:DOEA:NRR
 
DFischer*05/22/92 C/EMEB:DE:RES
 
MVagins*06/08/92 C/OGCB:DOEA:NRR
 
CHBerlinger*
06/10/92 RPB:ADM TechEd*05/22/92 D/DE:RES LCShao*06/08/92 7W ssi C/OEAB:DOEA:NRR
 
AChaffee*06/04/92 RVIB:NRR SAlexander*
06/30/92 Document Name: 92-51.IN
 
IN 92-XX June xx, 1992 This information
 
notice requires no specific action or written response.
 
If you have any questions
 
about the information
 
in this notice, please contact one of the technical
 
contacts listed below or the appropriate
 
Office of Nuclear Reactor Regulation (NRR) project manager.Charles E. Rossi, Director Division of Operational
 
===Events Assessment===
Office of Nuclear Reactor Regulation
 
Technical
 
contacts: Satish K. Aggarwal, RES (301) 492-3829 Stephen D. Alexander, NRR (301) 504-2995 Nick Fields, NRR (301) 504-1173 Attachment:
List of Recently Issued NRC Information
 
Notices Brian K. Grimes, Director, Division of Reactor Inspection
 
and Safeguards
 
and Ashok C. Thadani, Director, Division of Systems Technology
 
concurred
 
in a previous version of this information
 
notice. Notice was significantly
 
revised to remove "regulatory
 
guide" portions of original draft after above %y concurrences
 
were obtained.
 
C. E. Ros i;2r B a*SE PREVIOUS CONCURe RN-*SEE PREVIOUS CONCURRENCE
 
OEAB:DOEA:NRR
 
NFields*05/21/92 EMEB:DE:RES
 
SKAggarwal*
06/08/92 SC/OEAB:DOEA:NRR
 
DFischer*05/22/92 C/EMEB:DE:RES
 
MVagins*06/08/92 RPB:ADM TechEd*05/22/92 D/DE:RES LCShao*06/08/92 C/OEAB:DOEA:NRR
 
AChaffee*06/04/92 RVIB:NRRA SAlexander
 
06 / 0/92 SELB:NRR ASGill*06/29/92 C/OGCB:DOEA:NRR
 
CHBerlinger*
06/10/92 D/DOEA:NRR
 
CERossi/ /92 Document Name: C:\CIRBRK (ATB)
I I IN 92-XX May xx, 1992 This information
 
notice requires no specific action or written response.
 
If you have any questions
 
about the information
 
in this notice, please contact one of the technical
 
contacts listed below or the appropriate
 
Office of Nuclear Reactor Regulation (NRR) project manager.Charles E. Rossi, Director Division of Operational
 
===Events Assessment===
Office of Nuclear Reactor Regulation
 
Technical
 
contacts: Satish K. Aggarwal, RES (301) 492-3829 Stephen D. Alexander, NRR (301) 504-2995--Am itpa 1 -G-i-l1 NR (301t=043-i
 
Nick Fields, NRR (301) 504-1173 Attachment:
List of Recently Issued NRC Information
 
Notices Brian K. Grimes, Director, Division of Reactor Inspection
 
and Safeguards
 
and Ashok C. Thadani, Director, Division of Systems Technology
 
concurred
 
in a previousversion
 
of this informa ion no t iV >4 A/ ' N. r.t*Sv i!EE P RE VIOU SC NC OCUR'RE NC W -.)4 OEAB:DOEA:NRR
 
NFields*05/21/92 EMEB:DE:RES
 
SKAggarwal
 
&/ g /92 C/OGBJ NRR CHBe inger G/ Io192 SC/OEAB:DOEA:NRR
 
DFischer*05/22)si C/4A:RES MVagins C, /of/i92 D/DOEA:NRR
 
CERossi/ /92 RVIB :NRR SAlexander
 
06/ /92 C,- A B r-t" -RPB:ADM C/OEAB:DOEA:NRR
 
Tech Ed* Jt);,,4*Chaffee
 
05/2219 /9 / C/q/92 SELB: NR- ,, ASGill 06l97/92 Document Name: C:\CIRBRK (ATB)
I r -.'K-'IN 92-XX May xx, 1992 This information
 
notice requires no specific action or written response.
 
If you have any questions
 
about the information
 
in this notice, please contact one of the technical
 
contacts listed below or the appropriate
 
Office of Nuclear Reactor Regulation (NRR) project manager.Charles E. Rossi, Director Division of Operational
 
===Events Assessment===
Office of Nuclear Reactor Regulation
 
Technical
 
contacts: Satish K. Aggarwal, RES (301) 492-3829 Stephen D. Alexander, NRR (301) 504-2995 N raS.m l G1J4INRK Nick Fields, NRR (301) 504-1173 Attachment:
List of Recently Issued NRC Information
 
Notices Document Name: OEAB:DOEA:.
 
RR NFieldsfJ Y5/h4/92 EMEB:DE:RES
 
SKAggarwal
 
/ /92 D/DST:NRR ACThadani/ /92 C:\CIRBRK (ATB)SCREAB:DOEA:NRR
 
DFischer 5 /7-i/92 C/EMEB:DE:RES
 
MVagins/ /92 C/OGCB:DOEA:NRR
 
CHBerlinger
 
/ /92 RPB:ADM TechEd/ /92 D/DE:RES LCShao/ /92 GV fo JC C/OEAB:DOEA:NRR
 
AChaffee G/ 5/92 D/DRIS:NRR


IN 92-51July 9, 1992 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Original Signed byCharles E. RossiCharles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical contacts:Satish K. Aggarwal, RES(301) 492-3829Stephen D. Alexander, NRR(301) 504-2995Nick Fields, NRR(301) 504-1173Attachment:List of Recently Issued NRC Information NoticesBrian K. Grimes, Director, Division of Reactor Inspection and Safeguardsand Ashok C. Thadani, Director, Division of Systems Technology concurred in aprevious version of this information notice. Notice was significantly revisedto remove "regulatory guide" portions of original draft after aboveconcurrences were obtained. I determined it was unnecessary to have re-concurrence at the Division Director level. C. E. Rossi*SEE PREVIOUS CONCURRENCEOEAB:DOEA:NRRNFields*05/21/92EMEB:DE:RESSKAggarwal*06/08/92SELB:NRRASGill*06/29/92SC/OEAB:DOEA:NRRDFischer*05/22/92C/EMEB:DE:RESMVagins*06/08/92C/OGCB:DOEA:NRRCHBerlinger*06/10/92RPB:ADMTechEd*05/22/92D/DE:RESLCShao*06/08/927W ssiC/OEAB:DOEA:NRRAChaffee*06/04/92RVIB:NRRSAlexander*06/30/92Document Name: 92-51.IN
BKGrimes/ /92 D/DOEA:NRR


IN 92-XXJune xx, 1992 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical contacts:Satish K. Aggarwal, RES(301) 492-3829Stephen D. Alexander, NRR(301) 504-2995Nick Fields, NRR(301) 504-1173Attachment:List of Recently Issued NRC Information NoticesBrian K. Grimes, Director, Division of Reactor Inspection and Safeguardsand Ashok C. Thadani, Director, Division of Systems Technology concurred in aprevious version of this information notice. Notice was significantly revisedto remove "regulatory guide" portions of original draft after above %yconcurrences were obtained. C. E. Ros i;2r B a*SE PREVIOUS CONCURe RN-*SEE PREVIOUS CONCURRENCEOEAB:DOEA:NRRNFields*05/21/92EMEB:DE:RESSKAggarwal*06/08/92SC/OEAB:DOEA:NRRDFischer*05/22/92C/EMEB:DE:RESMVagins*06/08/92RPB:ADMTechEd*05/22/92D/DE:RESLCShao*06/08/92C/OEAB:DOEA:NRRAChaffee*06/04/92RVIB:NRRASAlexander06 / 0/92SELB:NRRASGill*06/29/92C/OGCB:DOEA:NRRCHBerlinger*06/10/92D/DOEA:NRRCERossi/ /92Document Name: C:\CIRBRK(ATB)
CERossi/ /92}}
I IIN 92-XXMay xx, 1992 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical contacts:Satish K. Aggarwal, RES(301) 492-3829Stephen D. Alexander, NRR(301) 504-2995--Am itpa 1 -G-i-l1 NR(301t=043-iNick Fields, NRR(301) 504-1173Attachment: List of Recently Issued NRC Information NoticesBrian K. Grimes, Director, Division of Reactor Inspection and Safeguardsand Ashok C. Thadani, Director, Division of Systems Technology concurred in apreviousversion of this informa ion no t iV >4A/ ' N. r.t*Sv i!EE P RE VIOU SC NC OCUR'RE NC W -.)4OEAB:DOEA:NRRNFields*05/21/92EMEB:DE:RESSKAggarwal&/ g /92C/OGBJ NRRCHBe ingerG/ Io192SC/OEAB:DOEA:NRRDFischer*05/22)siC/4A:RESMVaginsC, /of/i92D/DOEA:NRRCERossi/ /92RVIB :NRRSAlexander06/ /92C,- A B r-t" -RPB:ADM C/OEAB:DOEA:NRRTech Ed* Jt);,,4*Chaffee05/2219 /9 / C/q/92SELB: NR- ,,ASGill06l97/92Document Name:C:\CIRBRK (ATB)
I r -.'K-'IN 92-XXMay xx, 1992 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical contacts:Satish K. Aggarwal, RES(301) 492-3829Stephen D. Alexander, NRR(301) 504-2995N raS.m l G1J4INRKNick Fields, NRR(301) 504-1173Attachment: List of Recently Issued NRC Information NoticesDocument Name:OEAB:DOEA:. RRNFieldsfJY5/h4/92EMEB:DE:RESSKAggarwal/ /92D/DST:NRRACThadani/ /92C:\CIRBRK (ATB)SCREAB:DOEA:NRRDFischer5 /7-i/92C/EMEB:DE:RESMVagins/ /92C/OGCB:DOEA:NRRCHBerlinger/ /92RPB:ADMTechEd/ /92D/DE:RESLCShao/ /92GV fo JCC/OEAB:DOEA:NRRAChaffeeG/ 5/92D/DRIS:NRRBKGrimes/ /92D/DOEA:NRRCERossi/ /92  
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Revision as of 13:09, 31 August 2018

Misapplication and Inadequate Testing of Molded-Case Circuit Breakers
ML031200137
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, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant  Entergy icon.png
Issue date: 07/09/1992
From: Rossi C E
Office of Nuclear Reactor Regulation
To:
References
-nr IN-92-051, NUDOCS 9207020233
Download: ML031200137 (9)
v • d • e


JoS / KU UNITED STATES NUCLEAR REGULATORY

COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 July 9, 1992 NRC INFORMATION

NOTICE 92-51: MISAPPLICATION

AND INADEQUATE

TESTING OF MOLDED-CASE

CIRCUIT BREAKERS

Addressees

All holders of operating

licenses or construction

permits for nuclear power reactors.

Purpose

TheU.S. Nuclear Regulatory

Commission (NRC) is issuing this information

notice to alert addressees

to problems that were recently observed concerning

the application

and testing of molded-case

circuit breakers (MCCBs). 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 are not NRC requirements;

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

of Circumstances

During research and inspection

activities, the NRC staff has found that licensees, when determining

the MCCB parameters

for motor loads, occasionally

underestimate

or neglect to consider the inrush transient (starting)

current (ITC) occurring

during the first few cycles after a motor is started. Often only the locked rotor current (LRC) is considered

in selecting

the appropriate- MCCB.If no special starting methodology

is used to specifically

limit the ITC, the magnitude

of the ITC can be as much as approximately

three times the LRC.Also, depending

on the electrical

characteristics

of the power supply and the impedance

of the motor when started, the ITC can increase to as much as approximately

six times the value of the LRC. A current of this magnitude

is greater than the maximum instantaneous

trip setting for circuit protection

recommended

by the National Electric Code (NEC). Therefore, the NEC recommended

level of protection

may be insufficient

to prevent an unwanted trip. Proper application

of MCCBs depends strongly upon the use of accurate design assumptions.

Another application

problem involves the use of MCCBs equipped with both thermal overload trip elements and instantaneous

magnetic trip elements.

A newly purchased

replacement

Westinghouse

Type HFB3125 ambient compensating

MCCB tripped when a hydrogen skimmer fan motor at the Catawba Nuclear Station 7 9207020233

\J 1-IN 92-51 July 9, 1992 was started during testing after installation.

Duke Power Company personnel did not expect the MCCB to trip since the peak value of the ITC for the fan motor was thought to be well below the instantaneous

trip band of that MCCB (NRC Inspection

Report 99900404/90-01).

A similar Westinghouse

MCCB used as a turbine room sump pump breaker tripped in a similar manner at the Donald C. Cook Nuclear Power Plant. (NRC Inspection

Report 99900404/90-21).

Westinghouse

determined

that most of its thermal-magnetic

MCCBs with the nonadjustable

instantaneous

magnetic trip function could trip inadvertently.

Westinghouse

attributed

this behavior to interaction

between the thermal overload trip function and the instantaneous

magnetic trip function under overload conditions.

Under nonfault conditions, these functions

may interact when the circuit current causes the thermal trip element to deflect until it presses on the MCCB's tripper bar at the same time that the instantaneous

magnetic armature is vibrating

against the tripper bar. This interaction

causes the MCCB to trip.Westinghouse

notified nuclear licensees

of this problem and recommended

that they test these MCCBs in their intended circuits before releasing

them for plant operation.

Westinghouse

also stated this recommendation

on certificates

of conformance

provided with its dedicated

MCCBs sold as safety-related

items.Potential

interactions

between thermal overload and instantaneous

trip functions

can be avoided by using a special class of MCCBs that are designed specifically

for motor loads. These MCCBs include only instantaneous

magnetic trip functions

for protecting

against faults or short circuits.

The trip setpoints

are normally adjustable

and more accurate than those in thermal-magnetic MCCBs. These MCCBs, commonly referred to by the Westinghouse

term"motor circuit protectors," are intended for use in combination

with motor contactors

or starters.

Thermal overload relays contained

in the contactors

or starters provide the coordinated

protection

against overloads

and fault currents which are below the magnitude

necessary

to actuate an instantaneous

trip of the MCCB.Instances

of premature

tripping have occurred with MCCBs manufactured

by ITE-Siemens Company. The Carolina Power and Light Company, licensee for the Shearon Harris Nuclear Power Plant, found that some of the 480 volt MCCBs manufactured

by ITE-Siemens, and purchased

as commercial-grade, tripped prematurely

when tested (NRC Inspection

Report 99901177/90-01).

The licensee had purchased

these MCCBs as replacements

for some older 600 volt ITE-Siemens

MCCBs. The ITE-Siemens

Company tested the 480 volt MCCBs and found that these trips were initiated

by the MCCBs' instantaneous

magnetic trip function, when induction

motor loads were started. The manufacturer

tested the older 600 volt MCCBs and found no premature

trips. Rather, the older 600 volt MCCBs tripped at currents significantly

above the levels at which an instantaneous

trip should have occurred.

i X -X IN 92-51 July 9, 1992 The licensee's

testing of the 480 volt MCCBs was judicious.

ITE-Siemens

stated that the instantaneous

trip setpoints

of commercial

grade MCCBs-with

nonadjustable

magnetic trips are not normally-verified

at the factory.However, ITE-Siemens

and possibly other manufacturers

of MCCBs will, upon request, verify that the instantaneous

magnetic trip points of their commercial

grade MCCBs with nonadjustable

magnetic trips supplied to nuclear utilities

fall within the appropriate

design band. Nevertheless, field testing of other MCCBs may be needed to verify that their magnetic trip points occur within the-design

band (but not below the band) because other manufacturers

may not routinely

provide this verification

for commercial

grade MCCBs. For this type of MCCB, most manufacturers

check only that the MCCB will trip instantaneously, without determining

the current level at which the trip occurs.Discussion

An MCCB can render safety-related

equipment

inoperable

if it trips prematurely.

Premature

trips can result if the incorrect

MCCB is selected (and/or incorrectly

adjusted)

as a result of inadequate

analysis of the load circuit including

dynamic analysis of expected transients

when determining

ratings, settings and coordination

requirements.

Premature

trips can also-occur with properly applied and set MCCBs that are operating

out of tolerance when incorrect

bench testing methods and/or inadequate

post-installation

testing fail to detect the out of tolerance

performance.

Acceptable

testing methods and specifications

are provided in some MCCB manufacturers'

technical

publications.

Industry and professional

organizations

also provide guidance on MCCB testing methods, including

generic acceptance

criteria, in documents

such as the National Electrical

Manufacturers

Association (NEMA) Standard AB4-1991, "Guidelines

for the Inspection

and Preventive

Maintenance

of Molded Case Circuit Breakers Used in Commercial

and Industrial

Applications." It should be noted that the application

of generic field test tolerances

to the instantaneous

trip band on manufacturers'

time-current

characteristic

curves may not always ensure that the MCCBs meet plant-specific

breaker coordination, circuit protection

or technical

specification

requirements.

Testing of properly applied and set MCCBs in accordance

with industry recommended

practices

should provide reasonable

assurance

that the MCCBs'instantaneous

trip performance

is acceptable

for safety-related

applications.

IN 92-51 July 9, 1992 This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact one of the technical

contacts listed below or the appropriate

Office of Nuclear Reactor Regulation (NRR) project manager.ssi,D ide or Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

contacts:

Satish K. Aggarwal, RES (301) 492-3829 Stephen D. Alexander, NRR (301) 504-2995 Nick Fields, NRR (301) 504-1173 Attachment:

List of Recently Issued NRC Information

Notices

.-1<-'Attachment

IN 92-51 July 9, 1992 LIST OF RECENTLY ISSUED NRC INFORMATION

NOTICES Information

Date of Notice No. Subject Issuance Issued to 92-50 92-49 92-48 92-47 92-46 92-45 92-44 92-43 92-42 Cracking of Valves in the Condensate

Return Lines of A BWR Emer-gency Condenser

System Recent Loss or Severe Degradation

of Service Water Systems Failure of Exide Batteries

Intent

ional

Bypassing of Automatic

Actuation of Plant Protective

Features Thermo-Lag

Fire Barrier Material Special Review Team Final Report Findings, Current Fire Endurance Tests, and Ampacity Cal-culation Errors Incorrect

Relay Used in Emergency

Diesel Generator Output Breaker Control Circuitry Problems with Westing-house DS-206 and DSL-206 Type Circuit Breakers Defective

Molded Phen-olic Armature Carriers Found on Elmwood Con-tactors Fraudulent

Bolts in Seismically

Designed Walls 07/02/92 07/02/92 07/02/92 06/29/92 06/23/92 06/22/92 06/18/92 06/09/92 06/01/92 All holders for BWRs.of OLs or CPs 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.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.OL = Operating

License CP = Construction

Permit

IN 92-51 July 9, 1992 This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact one of the technical

contacts listed below or the appropriate

Office of Nuclear Reactor Regulation (NRR) project manager.Original Signed by Charles E. Rossi Charles E. Rossi, Director Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

contacts: Satish K. Aggarwal, RES (301) 492-3829 Stephen D. Alexander, NRR (301) 504-2995 Nick Fields, NRR (301) 504-1173 Attachment:

List of Recently Issued NRC Information

Notices Brian K. Grimes, Director, Division of Reactor Inspection

and Safeguards

and Ashok C. Thadani, Director, Division of Systems Technology

concurred

in a previous version of this information

notice. Notice was significantly

revised to remove "regulatory

guide" portions of original draft after above concurrences

were obtained.

I determined

it was unnecessary

to have re-concurrence

at the Division Director level. C. E. Rossi*SEE PREVIOUS CONCURRENCE

OEAB:DOEA:NRR

NFields*05/21/92 EMEB:DE:RES

SKAggarwal*

06/08/92 SELB:NRR ASGill*06/29/92 SC/OEAB:DOEA:NRR

DFischer*05/22/92 C/EMEB:DE:RES

MVagins*06/08/92 C/OGCB:DOEA:NRR

CHBerlinger*

06/10/92 RPB:ADM TechEd*05/22/92 D/DE:RES LCShao*06/08/92 7W ssi C/OEAB:DOEA:NRR

AChaffee*06/04/92 RVIB:NRR SAlexander*

06/30/92 Document Name: 92-51.IN

IN 92-XX June xx, 1992 This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact one of the technical

contacts listed below or the appropriate

Office of Nuclear Reactor Regulation (NRR) project manager.Charles E. Rossi, Director Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

contacts: Satish K. Aggarwal, RES (301) 492-3829 Stephen D. Alexander, NRR (301) 504-2995 Nick Fields, NRR (301) 504-1173 Attachment:

List of Recently Issued NRC Information

Notices Brian K. Grimes, Director, Division of Reactor Inspection

and Safeguards

and Ashok C. Thadani, Director, Division of Systems Technology

concurred

in a previous version of this information

notice. Notice was significantly

revised to remove "regulatory

guide" portions of original draft after above %y concurrences

were obtained.

C. E. Ros i;2r B a*SE PREVIOUS CONCURe RN-*SEE PREVIOUS CONCURRENCE

OEAB:DOEA:NRR

NFields*05/21/92 EMEB:DE:RES

SKAggarwal*

06/08/92 SC/OEAB:DOEA:NRR

DFischer*05/22/92 C/EMEB:DE:RES

MVagins*06/08/92 RPB:ADM TechEd*05/22/92 D/DE:RES LCShao*06/08/92 C/OEAB:DOEA:NRR

AChaffee*06/04/92 RVIB:NRRA SAlexander

06 / 0/92 SELB:NRR ASGill*06/29/92 C/OGCB:DOEA:NRR

CHBerlinger*

06/10/92 D/DOEA:NRR

CERossi/ /92 Document Name: C:\CIRBRK (ATB)

I I IN 92-XX May xx, 1992 This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact one of the technical

contacts listed below or the appropriate

Office of Nuclear Reactor Regulation (NRR) project manager.Charles E. Rossi, Director Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

contacts: Satish K. Aggarwal, RES (301) 492-3829 Stephen D. Alexander, NRR (301) 504-2995--Am itpa 1 -G-i-l1 NR (301t=043-i

Nick Fields, NRR (301) 504-1173 Attachment:

List of Recently Issued NRC Information

Notices Brian K. Grimes, Director, Division of Reactor Inspection

and Safeguards

and Ashok C. Thadani, Director, Division of Systems Technology

concurred

in a previousversion

of this informa ion no t iV >4 A/ ' N. r.t*Sv i!EE P RE VIOU SC NC OCUR'RE NC W -.)4 OEAB:DOEA:NRR

NFields*05/21/92 EMEB:DE:RES

SKAggarwal

&/ g /92 C/OGBJ NRR CHBe inger G/ Io192 SC/OEAB:DOEA:NRR

DFischer*05/22)si C/4A:RES MVagins C, /of/i92 D/DOEA:NRR

CERossi/ /92 RVIB :NRR SAlexander

06/ /92 C,- A B r-t" -RPB:ADM C/OEAB:DOEA:NRR

Tech Ed* Jt);,,4*Chaffee

05/2219 /9 / C/q/92 SELB: NR- ,, ASGill 06l97/92 Document Name: C:\CIRBRK (ATB)

I r -.'K-'IN 92-XX May xx, 1992 This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact one of the technical

contacts listed below or the appropriate

Office of Nuclear Reactor Regulation (NRR) project manager.Charles E. Rossi, Director Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

contacts: Satish K. Aggarwal, RES (301) 492-3829 Stephen D. Alexander, NRR (301) 504-2995 N raS.m l G1J4INRK Nick Fields, NRR (301) 504-1173 Attachment:

List of Recently Issued NRC Information

Notices Document Name: OEAB:DOEA:.

RR NFieldsfJ Y5/h4/92 EMEB:DE:RES

SKAggarwal

/ /92 D/DST:NRR ACThadani/ /92 C:\CIRBRK (ATB)SCREAB:DOEA:NRR

DFischer 5 /7-i/92 C/EMEB:DE:RES

MVagins/ /92 C/OGCB:DOEA:NRR

CHBerlinger

/ /92 RPB:ADM TechEd/ /92 D/DE:RES LCShao/ /92 GV fo JC C/OEAB:DOEA:NRR

AChaffee G/ 5/92 D/DRIS:NRR

BKGrimes/ /92 D/DOEA:NRR

CERossi/ /92


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