Fault Level

based on the Xd'', Xd' and Xd of the generator

Please can you give the formula of same?

Epressions for SC are;

I" = E/X"d, Where X"d is the apparant reactance of the stator winding just at the instant of SC (during the first few cycles, it causes heavy current to flow)and E is the phase voltage.

I' = E/X'd, Where X'd is the transient reactance which takes into account the armature and leakage reactance.

I' = E/Xd, Where Xd is synchronous reactance (used primarily for relay settings)

If I can modify a bit:

I"k = E"/X"d

I'k = E'/X'd

Ik = E/Xd

Not to ignore the time constants, T"d & T'd

Fault level of alternator (in MVA) =

Capacity(in MVA) of alternator / Sub-transient impedance (Xd") of alternator