ML20141E119

Forwards Draft NRC in, Potential of Incorrectly Wired or Assembled Abb K-Line Metal-Clad Low-Voltage Circuit Breakers. Proprietary Abb K-Line Power Shield Wiring Diagram (Drawing 709551,Rev 16) Encl.Diagram Withheld

ML20141E119
Person / Time
Site:	Perry
Issue date:	06/27/1997
From:	Chaffee A NRC (Affiliation Not Assigned)
To:	Rennie J AFFILIATION NOT ASSIGNED
Shared Package
ML19317C471	List: ML20141E119
References
NUDOCS 9706300231
Download: ML20141E119 (4)

Text

._ . __ _ . . _ . -._. _-. - _.__ _ _.. _ _. _ -..-.._.._ _ _._ _ . _ _ . _ - _

, if, e June 27, 1997 l

l Mr. Jon S. Re, nit

! Total Quality Managar '

Distribution Systems Division ABB Power T&T Company, Incorporated 201 hickman Drive Sanford, FL 32771

SUBJECT:

REQUEST FOR A TECHNICAL REVIEW OF A DRAFT INFORMATION NOTICE REGARDING INCORRECTLY WIRED CURRENT SENSORS IN ABB K-LINE CIRCUIT BREAKERS

Dear Mr. Rennie:

l The U.S. Nuclear Regulatory Commission (NRC) is planning to issue an information notice on the miswiring of the current sensors in ABB K-line circuit breakers. We ask that you review the enclosed draft of that information notice to ensure the technical information is accurate. Your cooperation in this matter is appreciated. Please return any comments you may ,

l have as soon as aossible. A copy of this request and your response will be '

' placed in the Pu)lic Document Room for review by the public. Your response l should be mailed to: l l U.S. Nuclear Regulatory Commission ATTN: David Skeen. NRR/PECB Mail Stop: 0-11-E4 l Washington. DC 20555-0001 Please address any rpestions you may have on this matter to David Skeen of my  !

staff. Mr. Skeen may be reached by phone (301) 415-1174 or e-mail at  !

DLS@NRC. GOV. If no comments are received by close of business on July 11,  ;

1997, we will assume the technical information in the notice is correct. '

Sincerely, l Original signed by Edward F. Goodwinl for Alfred ~ E. Chaffee, Chief Events Assessment and Generic Communications Branch Division of Reactor Program Management 300000 Office of Nuclear Reactor Regulation cc: J.J. Connoly

Enclosure:

Draft Information Notice 7

DISTRIBUTION:

SCentraloFiles DRPM R/F PDR PECB R/F MMSlosson AEChaffee DLSkeen i Filename: G:\DLS\ABB-CT.LTR DFo3  ;

0FFICE PECB:NRRn cSf/)PECB;fMR C/PECB:NRR _

OECB D$ keen U O k D fn [ AChaffee @ f Dth'llb f DATE 06/2 7/97 ' 06h /97 06/297 l JFFICIAL RECORD COPY 9706300231 970627 PDR ORG NRRA PDR

lJ'"

DRAFJJ UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, D.C. 20555-0001 June xx, 1997 NRC INFORMATION NOTICE 97-XX: POTENTIAL FOR INCORRECTLY WIRED OR ASSEMBLED ABB K-LINE METAL-CLAD LOW-VOLTAGE CIRCUIT BREAKERS Addressees All holders of operating licenses or construction permits for nuclear power reactors.

Purcose The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert addressees that the potential exists for ASEA Brown Boveri (ABB) K-Line metal-clad low-voltage circuit breakers to be incorrectly wired or assembled, and these errors may not have been identified due to ineffective verification of the operation of the solid state trip device, and ineffective verification of the secondary wiring. As a result, loss of multiple safety functions may occur. It is expected that recipients will review the information for applicability to their facilities and consider actions, as i 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.

Descriotion of Circumstances On September 16. 1996, while operating at full power, an ABB type K600S 480-Vac circuit breaker prematurely tripped on overcurrent at Centerior Energy Company's Perry Nuclear Power Plant (Perry) and de-energized a safety-related motor control center (MCC). The circuit breaker's SS-5 solid state trip device (Power Shield), sensed an overcurrent condition esen though actual MCC current at the time of the trip was well below the Power Shield's expected trip set point. Subsequent inspection of the circuit breaker determined that phase C current transformer (CT) sensor wires were reversed, resulting in the polarity of the sensor being reversed. Three-phase testing of the breaker at ABB's circuit breaker manufacturing facility test laboratory in Florence SC, showed that the breaker consistently tripped between 350-360 amps, much below the Power Shield's expected overcurrent trip set point of 660 amns.

Discussion Other ABB K-Line low voltage circuit breakers equipped with solid state trip units have also tripped unexpectedly after being placed into service, due to l incorrectly wired or installed cts. The unexpected trips were due to the polarity sensitivity of ABB's 3-phase solid state trip units. Incorrectly wired or installed cts have a 180 degree phase shift in their output currents which may cause the trip units to actuate at a primary current level l signi ficantly below the expected level . Because single-phase primary current GnO a~ ew

[ IN 97-XX k July XX. 1997 Page 2 of 3 calibration or testing does not detect phase shift or CT secondary output current. Other testing or inspections are necessary to verify proper operation of ABB's solid state trip units and verification of the secondary wiring should also be consistently and effectively implemented.

The K600S breaker that tripped due to reversed CT wires at Perry was a new breaker manufactured at ABB Power Transmission & Distribution (T&D) Company.

Incorporated Distribution Systems Division (ABB Power T&D). facility in Florence. S.C. On March 26, 1997. ABB Power T&D informed the NRC of a Dotential defect in the K-line circuit breakers equipped with the " Power Snield" solid state trip device. The' report indicated that the trip device could trip below the trip setting if the circuit breaker's overcurrent sensing cts are incorrectly connected to the Power Shield trip device. Although the circuit breaker which tri) ped prematurely at Perry was a new circuit breaker.

K6005 breakers that have )een refurbished by ABB Service Incorporated facilities have also been found to contain similar CT or wiring problems.

Therefore, the wiring defect identified at Perry could potentially be found in refurbished. as well as new circuit breakers.

A ty)ical ABB K-Line metal-clad low voltage circuit breaker has six cts. three of w1ich are referred to as phase sensors, and are used to detect fault currents (see attached wiring diagram). The remaining three cts are referred to as power sensors. and are used to develop a trip reference signal within the trip unit. Two cts are installed on each phase of the circuit breaker; one phase sensor and one power sensor. The leads from all six cts are terminated on three terminal blocks attached to the lower molding of the circuit breaker. These three terminal blocks are connected to the trip unit by a multiconductor cable. Ty]ical wiring and assembly errors that have been discovered in new and refurbisled ABB K-line circuit breakers include:

o CT leads terminated on the wrong terminals of the lower terminal blocks; e Multiconductor cable conductors terminated on the wrong terminals of the  ;

lower terminal blocks or on the wrong terminals of the Power Shield Trip Unit:

e cts installed upside down, but correctly terminated on the lower terminal blocks (same effect as reversing the leads).

Additionally. ABB Power T&D has found that the potential of miswiring can occur during different operations. For example, when the wires on terminals

6. 7. and 8 of the Power Shield trip unit are lifted to perform continuity checks of the phase sensors, or the wires on terminals 11, 12. 13. and 14 are lifted to conduct calibration tests. the wires can be relanded incorrectly. '

Circuit breaker wiring or assembly errors can be introduced by the original equipment manufacturer, companies performing circuit breaker refurbishment services or utilities during testing. Incorrectly wired or assembled circuit breakers might be presently in service or stored in a warehouse for service at a later date. Because single phase calibration testing, similar to that performed at the ABB manufacturing facility. does not adequately verify the overcurrent trip set points of some circuit breakers equipped with three phase k

H' l

i DRAFT, IN 97-XX July XX. 1997 Page 3 of 3 l

l solid state trip units. the potential exists for incorrectly wired or l- assembled circuit breakers to pass calibration testing, but trip during a l

design basis accident resulting in a loss of safety functions.  ;

i ABB Power T&D informed its customers of record of the potential defect. -

However, because some licensees may have purchased breakers through a third l party supplier, or may have had breakers refurbished by a third party contractor, this notice is being issued to ensure that all potentially affected licensees receive the information.

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact i one of the technical contacts listed below or the appropriate Office of l Nuclear Reactor Regulation (NRR) project manager.

Marylee H. Slosson Acting Director Division of Reactor Program Management Office of Nuclear Reactor Regulation ,

Technical contacts: Donald Kosloff. R-III J.J. Petrosino. NRR

! 216-259-3610 301-415-2979 E-mail: dck@nrc. gov E-mail: jjpl@nrc. gov

!. Virgil Beaston, NRR David Skeen. NRR M l

301-415-5774 E-mail: vlb@nrc. gov 301-415-1174 E-mail: dis @nrc. gov

\,3 %

l  !

l

Attachment:

ABB K-Line Power Shield Wiring Diagram - Drawing 709551. Rev 16 I

i i

l

_ _ _