GE Power Vac Failure

[pwrengrds]

5kV GE Power Vac 1200 amp breakers are being used for motor starters to start a 1061 amp motor. They have been in service since 1980. We have had two failure in the past couple of months involving the line side stabs failing during motor starts. The stabs are vaporized, the breaker ejected from the cell, and the 3000 amp main clears the fault.

Has anyone else seen this type of fault?

Is it due to the stabs that are worn out or the breakers?

Any advice on stopping this fault from happening would be appreciated.

 

[mlhspike]

I have seen similar faults before and I would look into the grease you are putting on the fingers of the breaker during service, it might of changed since 1980 and the old grease is still on the stabs. Some of the greases don't mix well and you might have this building up over time resulting in poor contact. We label the breakers we rebuild with the type of grease we use to prevent mix and match of greases, you might try this for your cubicle stab to breaker connections.

 

[unclebob]

Looks like it had very loose finger clusters. Or something went wrong when racking it in. It's hard to measure the connection resistance of those hidden connections. You need a 100 A ducter and some space in the rear to access the bars and measure the resistance from behind, on the 3 phases. Not something we usually do tough. I wouldn't put grease on the stabs or fingers especially in dirty environment and if maintenance is done regularly. You always put too much of it.

 

[Zogzog]

There were some documented issues with the 3000A stabs failing but nothing I have heard about 1200A stabs.

Motor starter duty is tough on breakers, what type of maintenence plan do you have in place? (How often, to what extent. etc..)

 

[waross]

As dramatic as the picture may be, it does not provide a lot of information. Can you post a picture of the actual damage to the stabs?

Bill
--------------------
"Why not the best?"
Jimmy Carter