Generator/transformer circuit breaker

[genhead]

We have a 415v 2Mva generator connected via a circuit breaker to a 415/6.6kv transformer. The complete unit is trailer-mounted. We intend to use it to temporarily supply some 6.6kv plant. What protection is required on the 6.6kv outgoing supply?

 

[ScottyUK]

Does the generator have its own protection on the LV system? Assuming it does, a minimum of: overcurrent, short-circuit, earth fault.


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Sometimes I only open my mouth to swap feet...

 

[genhead]

Yes ScottyUK, there is overload, short circuit & earth fault protection on the LV side.
Would it be acceptable to fit a protection relay on the HV side, which trips the LV circuit breaker? i.e. no HV circuit breaker.

 

[moreause]

yep that would be like opening a upstream breaker

i just wonder how the generator will do with the transformer inrush...probably will just lower voltage a bit

 

[ScottyUK]

Sorry for my badly worded post. I would expect overcurrent, short-circuit, earth fault on the HV side if it is feeding a switchboard. The LV side should have a more extensive set of functions, mainly intended to protect the generator.


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Sometimes I only open my mouth to swap feet...

 

[dpc]

As long as you are not connected to the grid or another generator, you might get by without a high voltage breaker or fuses. Not necessarily recommended, but on a temporary basis it's probably acceptable. If you are paralleling generators on the high side or connecting to grid, you must have some means of disconnecting the transformer high side from the system.

A ground fault relay on the high side to trip the LV breaker would be a good idea, if the primary winding is to be grounded.