Vacuum Interrupter Testing

Hello everybody, I have a question that has me stumped and looking for an answer. For example 15kv vacuum breaker but the customer is only using 6.9kv on that breaker. Do you still test that breaker to NETA standards? Or do you test it at a lower voltage since they are using only 6.9 kv? Still new in the field just trying to find some answers? No one at my work is giving me a start answer

Thank you

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Hi Eric,

It depends on the application, but If it was me I would test it to the rating of the CB.

  1. It will cover you if at some stage in the future the main incoming voltage changes to let’s say 11kV or any voltage up to the rating of the CB.

Since the incoming supply voltage for your case is 6.9kV, testing the CB to the rated voltage will cover you in all bases.

Hope this helps,


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Per NETA the apparatus should be tested per rated voltage per manufacturer specs.

Also, 6.9kV seems like an odd voltage to be using, and my first question is if that is phase to ground voltage (where line-to-line would be 12kV) or actually line-to-line voltage. Either way the breaker is tested per manufacturer specs and manufacturer manuals don’t give various ratings for breakers based on operating voltages, they give specific overpotential values for the rated voltage of the breaker. NETA references manufacturer specs prior to relying on the tables found in NETA.