A 1000-MVA, 20-kV, 60-Hz, three-phase generator is connected through a 1000-MVA, 20-kV, /345-kV, Y transformer to a 345-kV circuit breaker and a 345-kV transmission line.

A 1000-MVA, 20-kV, 60-Hz, three-phase generator is connected through a 1000-MVA, 20-kV,

  

 Δ/345-kV, Y transformer to a 345-kV circuit breaker and a 345-kV transmission line. The generator reactance's are   

per unit, and its time constants are

 The transformer series reactance is 0.10 per unit; 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 the rated terminal voltage and at no-load. The breaker interrupts the fault three cycles after fault inception. Determine (a) the sub-transient current through the breaker in per-unit and in kA RMS and (b) the terms asymmetrical fault current the breaker interrupts, assuming maximum de offset. Neglect the effect of the transformer on the time constants.  

X", = 0.17, X, = 0.30, and X = 1.5