Main Breaker tripping constantly, what is the problem?

[zach.bes]

Not sure what you mean by 400A breaker with 300A shunt? (300A trip setting maybe?) Did you do any commissioning tests on the breaker? What type of breaker and trip unit do you have?

Did not run any tests on breaker. But am now. You don't expect a new breaker to be faulty.


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[zog]

Did not run any tests on breaker. But am now. You don't expect a new breaker to be faulty.


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It happens, they are only batch tested at the factory. That's why there are commissioning standards for testing them.

 

[Electric-Light]

are the neutrals on the 12kV side connected together through ground?