Medium Voltage Circuit Breaker Questions.

[living2learn]

Q1) I have come accross a medium voltage circuit breaker that originally was installed as a feeder breaker to a building. It is being upgraded right now to provide a feed from a generator. The relays are being swapped out and etc. Can this breaker which has labels stating "line" "load" be swapped?

Q2) Is there anything preventing a different installation from "double lugging" a medium voltage circuit breaker. It has a seperate relay for each set of conductors.

Thanks,

 

[cranky108]

A1) In general yes they can be swapped. However, there are a few out there that are specific for one reason or another. So investigate.

A2) I don't understand the question.

 

[ScottyUK]

Check the breaker is suitable for generator duty. Generators usually cause a very high X/R ratio and there is a long delay until the first current zero crossing, which usually means that the breaker can't interrupt a fault until the zero crossing. Most distribution breakers can't deal with this. Sometimes manufacturers of distribution breakers will deliberately delay the breaker opening command until the breaking conditions are favourable to avoid prolonged arcing on the contacts.

Proper generator breakers are available, but they are big and expensive. You might reflect on the reasons why they are big and expensive.


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