A 1000MVA, 20kV, 60 Hz three phase generator is connected to aninfinite bus through a 1000MVA, 20kV? / 345kVY transformer to a345kV circuit breaker and a 345kV transmission line. The generatorreactances are X``d=0.17, X`d=0.30, and Xd=1.5 per unit on a1000MVA, 20kV base. Generator time constants are T``d=0.05 seconds,T`d=1.0 seconds, and TA=0.10 seconds. The transformer seriesreactance is 0.10 per unit on the transformer ratings as a base.Neglect transformer losses, excitation current, and transformertime constants. The far end of the line is considered to be aninfinite bus operating at 1.0 per unit voltage on the transformerratings as a base. The line reactance is +j0.20 per unit on thesame base as everything else. A three phase short circuit occurs onthe line side of the transformer when the generator operates at noload. Breakers interrupt the fault three cycles after it begins.Determine the subtransient current through the transformer in perunit and the rms asymmetrical fault current that the breakersinterrupt assuming maximum dc offset.
