Short Circuit Calculation

I doubt there is a simple or clear-cut calculation for this; it may depend more on specific manufacturers' data.

IEC60909

http://users.ntua.gr/stpapath/Paper_2.52.pdf

http://www2.schneider-electric.com/documents/technical-publications/en/shared/electrical-engineering/electrical-know-how/low-voltage-minus-1kv/ect158.pdf

Note pages 9 and 10.

More precisely, IEC-60909 part-0 and part4. Part-0 given steps of calculation and formula and part-4 gives working examples. It is not possible to give all exact details here. Indicative general formula I can suggest you for transformer secondary of 2000kVA, 415V with %z of 6.25% the short circuit current formula will be VA/ 1.732xzxV dat gives answer of 44.5kA about. But, yes this is indicative just for quick feel of our SC level not exact. But, as a curiosity this can fulfil your need, I hope. Please note, though above example given is related to transformer you may do it on parallel lines for generator provided you know generator "initial sub-trasient reactance X" and voltage and MVA", this data given by manufacturer on name plate. Z=kx(R+jX") for generator. k is correction factor of generator for generator impedance. R =0.05 of X"up to 100MVA machines. This data is for your quick feel and help, however please refer relevant IEC -60909 parts for details. generally Generator X" can be considered about 12-14%. now you can calculate further.