Thank you Dr. P Sarajcev.

3 phase fault is the severe fault at the generator system as it involves no negative reactance

3L-G fault is most severe

Symmetrical fault is most severe

LLLG (line to line to line and ground)is the most severe fault for generators and will damaged maximum to generator with same current(fault) level of other types of faults.

L-L and L-G

L-G is most severe when the generator is solidly grounded only i.e. the grounding resistance is zero, other wise the equation for L-G will contain 3Rg ( grounding resistance) and three phase fault will be larger

symmetrical faults are most severe faults that may occur in Power systems. same stands true for generators

Symmetrical fault is the most sever fault

Three-line fault is the most sever fault.