Generator reactances

SCR (short circuit ratio) = Excitation current at rated voltage in OC condition/ Excitation current at rated                                                      voltage in sc condition

                                     = 1/ direct axis

Generator reactants (per unit)

 

	Typical Range	Effective time	Condition
X’’d	0.09-0.22	0 to 6 cycles	Maximum instantaneous current & current at time  circuit breaker usually open
X’d	0.13-0.20	6 cycles to 2 sec	Current at short time delay of CBs
Xd	1.0-2.5	After 2 sec	Steady state current without excitation support
X0	0.06-0.15		L-G fault current
X2	0.10-0.22		L-L fault current