ML20137F322

Part 21 Rept Re Perry Nuclear Power Plant Experiencing False Trip of K600S K-Line Low Voltage Circuit Breaker w/SS-5 Solid State Trip Device.Breaker Removed from Svc & Returned to Abb for Analysis

ML20137F322
Person / Time
Site:	Perry
Issue date:	03/26/1997
From:	Hagenhoff N, Rennie J ASEA BROWN BOVERI, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-PT21-97 NUDOCS 9704010062
Download: ML20137F322 (2)

Text

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. Page1 Document Control Desk 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 i

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), l with an SS-5 solid state trip device. At the time of the trip, the breaker's trip setting was i 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.

G 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 9704010062 970326 ' f n

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201 Hickrnan Drive 407 323-8220 407 322-8934 (Marketing /Engineenng)

Sanked. FL 32771-8201 407 322 8938 (Operations) 407 328-9264 (Hurnan Resources)

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. 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 l l if this condition existed elsewhere in the commercial or nuclear industry. The search, l i

completed on March 15,1997, revealed that there are n_g other known reports of false trips on new K-Line circuit breakers. However, througn 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. j

, 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 i

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 j grior to shipment. Maintenance and Surveillance Bulletin MS 3.1.1.9-2, Low Voltage  ;

Switchgcar Equipment, was revised to recommend that the trip unit be tested and the .

wiring verified by the end user upon installation of this equipment. I

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i 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.

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Any questions conceming this notification should be directed to Jon Rennie 407-323-8220 or Shannon Soupiset 803-665-4144.

/W /@o P epar rd By Reviewed By j J Rennie Norbert Hagenhoff

Total Quality Manager Vice President / General Manager Distribution Systems Division Distribution Systems Division i

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