high side (Y side) is 345 kV. The generator reactances are X = 0.17 pu, X = 0.30 pu, Xa = 1.5 pu,and its time constants are T 0.05 s,T 1.0 s,TA = 1.10 s. The transformer series reactance is 0.1pu; transformer losses and exciting current are neglected. A three-phase short-circuit occurs on the line side of the circuit breaker when the generator is operated at rated terminal voltage and at no-load. The breaker interrupts the fault three cycles after fault inception. Determine (a) the subtransient current through the breaker in per unit and in kA RMS. (b) The RMS asymmetrical fault current the breaker interrupts,assuming maximum de offset. Neglect the effect of the transformer on the time constants.

Fig: 1