fault level

[murdock]

anyone know the calculation to work out what the fault level (short circuit current) is 5 metres away from a 40 kva 400 volt 3 phase generator if i am using a 16 mm x 4 core ecc cable.

known...
40 kva
400 volts
58 amps
generator impedance unknown

i dont want the answer i want the formula and what the impedance of the 40 kva generator.

[AndyD]

Are you going to work it out from test readings or from manufacturers published figures?