United States Nuclear Regulatory Commission - Protecting People and the Environment


ACCESSION #: 9704010062



                                   ABB

Document Control Desk                                              Page 1

U.S.  Nuclear Regulatory Commission

Washington, DC 20555



March 26, 1997



Subject:  Notification of Potential Defect per 10CFR Part 21

          K-Line Low Voltage AC Circuit Breakers



Notification By: ABB Power T&D Co., Inc.

                 Distribution Systems Division

                 201 Hickman Dr.

                 Sanford, FL 32771



On September 16, 1996, Perry Nuclear Power Plant (Perry, OH), experienced

a false trip of a K600S K-Line Low Voltage Circuit Breaker (Serial Number

934277-031295), with an SS-5 solid state trip device.  At the time of the

trip, the breaker's trip setting was set at 660 amps and the breaker was

reported to be under approximately 50% load conditions.  The breaker was

removed from service and returned to ABB for analysis.



On October 8, 1996, the breaker was inspected at the ABB circuit breaker

manufacturing facility in Florence, SC.  The circuit wiring was checked

per the appropriate wiring diagram.  The phase C current transformer

sensor wires were found to be crossed (i.e.  the blue wire of terminal #2

was fastened to terminal #1 and the yellow wire of terminal #1 was

fastened to terminal #2).  The result was that the polarity of the sensor

was reversed.  Three phase testing at our facility's power laboratory

showed that, with the leads reversed, the breaker consistently tripped

between 350 and 360 amps, well below the 660 amp trip setting of the

breaker's trip unit.  After placing the leads in their correct position,

subsequent testing showed no other false trips.



The cause of this condition was human error in the wiring of this low

voltage circuit breaker during the manufacture of this product in our

Florence, SC facility, in March of 1995.  The inadvertent reversal of

these leads caused an errant, phase-shifted signal to be sent from the

phase C current transformer to the breaker's solid state trip unit.  This

errant signal caused the trip unit to sense an abnormally high current

reading, tripping the breaker.  This problem is only apparent when three

phase current is applied to the circuit breaker.  Production testing,

conducted in accordance with ANSI C37.50-1989, uses three separate single

phase tests to check the trip point of the trip unit.



The following processes to prevent this type of error were in place at

the time of the error.  The wiring diagram, the controlling document for

this process, was correct and available to the assembler.  The

individuals performing this function were trained



                       ABB Power T&D Company Inc.



     Distribution Systems Division   Telephone:   Telefax:

     201 Hickman Drive               407 323-8220 407 322-8934

     Sanford, FL 32771-8201                       (Marketing/Engineering)

                                                  407 322-8938

                                                  (Operations)

                                                  407 328-9264

                                                  (Human Resources)



                                   ABB                             Page 2



regularly on how to properly wire these devices.  The individual leads

were color coded to aid in proper placement.



This is the first and only report of this condition received by us in

over 7,500 commercial grade and safety related breakers produced since

1990.  For this reason ABB has been handling this issue as an isolated

incident related to a personnel error.  Since the first report of this

occurrence, ABB has conducted an industry search to see if this condition

existed elsewhere in the commercial or nuclear industry.  The search,

completed on March 15, 1997, revealed that there are no other known

reports of false trips on new K-Line circuit breakers.  However, through

this search, ABB has found that many K-Line breakers are now being re-

furbished in the nuclear industry.  These refurbishments are being done

by various end users and companies, many of which are not affiliated with

ABB.  If there is human error in the refurbishment process, this

condition could exist on these circuit breakers also.



The following corrective actions has been taken since the time of the

reported error.  The entire Low Voltage Team in Florence, SC was trained

on this incident, wiring procedures, and attention to detail in the

wiring of these current sensors.  This specific condition was added to

the Low Voltage Checklist for final quality inspection to verify prior to

shipment.  Maintenance and Surveillance Bulletin MS 3.1.1.9-2, Low

Voltage Switchgear Equipment, was revised to recommend that the trip unit

be tested and the wiring verified by the end user upon installation of

this equipment.



Although this faulted condition would already be apparent on any breaker

that is loaded greater than 50% of its trip value, ABB is recommending

that all ABB K-Line Low Voltage Circuit Breakers, both new and

refurbished, with solid state trip units, be inspected to verify the

proper wiring of these current transformer sensors.



ABB will notify all customers who purchased this product.



Any questions concerning this notification should be directed to Jon

Rennie 407-323-8220 or Shannon Soupiset 803-665-4144.



Prepared By                        Reviewed By

Jon S. Rennie                      Norbert Hagenhoff

Total Quality Manager              Vice President/General Manager

Distribution Systems Division      Distribution Systems Division



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