MV Circuit Breaker Failure Mode

[brupp]

In justifying the purchase of a spare 13.8 kV breaker for a 15kV metal-clad lineup I was asked a question about the failure modes of a medium voltage breaker. Our breakers are vacuum interrupter type. I've heard of catastrophic breaker failures happening, but the ones I'm most interested in are failures that would require repair or replacement of the circuit breaker without replacing the entire switchgear lineup or the building, as may be the case with a catastrophic failure.

Logically I would think that the charging and operating mechanisms would be likely failure points, as well as the vacuum bottles. I suppose auxiliary switches, limit switches, and solenoids could fail but that probably wouldn't require replacement of the breaker.

Can anyone suggest statistical or other information that would support or oppose arguments for buying a spare breaker versus buying replacement parts?

 

[busbar]

It's possible that NETA [netaworld.org] may have some data that supports their product—switchgear maintenance. I believe currently some of their published articles are available online without membership.

 

[PWR]

How many breakers do you have? What manufacturer/model? What is the environment in which they are operated? Are the mains and ties the same ampacity? What is the age? How often are/have they been serviced? Who performs the service? What is the cost of downtime if a spare has to be brought in and where would it come from?

As an engineer that works at a company that services circuit breakers (and stocks a number of mv air and vacuum units) those would be some of the questions I would ask before advising whether a spare unit is justified.

 

[jbartos]

Suggestion to the original posting:
The manufacturer tech support is in the better position to provide any reliability information regarding MV switchgear and its components or replacement parts. E.g. visit

http://www.schneider-electric.ca/

http://www/en/products/switchgear/html/clad.htm

http://www.schneider-electric.ca/

http://www/en/products/switchgear/F6055BR9801EP.pdf

http://www.powerconcorp.com/docs/PC-260 - VL Switchgear.pdf

(check a set of replacement parts on the picture)

http://gess.ge.com/pdf/gea-400wav32.pdf

etc. for more info

 

[alehman]

In my experience common failures in commissioning of new breakers include cell position contacts, aux switches, motors, secondary contacts. Bent cell rails are common. Mechanical linkages sometimes fail but those are commonly manufacturing defects (e.g. missing cotter pins).