Joslyn breaker

[ppaya]

12kV cable feeds furnace transformer (delta primary) via load break switch and Joslyn vacuum bottle breaker.
We just had another failure of the vacuum bottle. Operator thought all three phases were open (one was not due to failed bottle) and when he closed breaker there was big explosion. One of arrestors on the primary of the transformer blew up.
I am trying to find best manufacturer for 10,000 operations of the switch and breaker per year. I hope to get as much "life" out of them as possible.
Is vacuum best medium for this application?
What load-break switch do you recommend?

 

[matwong]

What is your specification of the breaker ? Does the present one comply with it ?
I don't really understand when you say that one phase of the breaker is not 'openned' and closing of the other 2 phases caused explosion ?? Isn't that is more hazardous when one of the phases is live when it supposes to be dead ?