Generator Fault Current

[Mike01]

Is there a way to get a rough estimate of fault current produced by a generator, prior to completing a fault study, would it be applicable to say a 2500kva generator will have approx the same fault current as a 2500kva xmfr?

 

[jim dungar]

Is there a way to get a rough estimate of fault current produced by a generator, prior to completing a fault study, would it be applicable to say a 2500kva generator will have approx the same fault current as a 2500kva xmfr?

Contact your generator manufacturer and ask for the subtransient reactance (Xd"). Xd" of a generator is similar to the %Z of a transformer. They should also be able to tell you what the fault output of your generator is (many have protective circuitry that limit them to about 3x FLA after the first few cycles).

From a short circuit stand point, single (not paralleled) generators deliver relatively low fault currents. From an arc flash incident energy point, this low fault current results in extremely long fault clearing times.

 

[ron]

As a guess, you could use an x"d of 15% which would mean that you take the FLA output times (1/.15)
or for a 2500kW gen @ 480V
3763A*6.667 = approx 25kA