A 1000-MVA 20-kV, 60-Hz three-phase generator is connected through a 1000-MVA 20-kV ?/138-kV Y transformer to a 138-kV circuit breaker and a 138-kV transmission line. The generator reactances are ??=0.15, ? =0.45 and =1.8 pu. The transformer series reactance is 0.1 pu; transformer losses and exciting current are neglected. A 3-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. Determine the substransient current through the breaker in pu and in kA rms ignoring any dc offset.

Question

A. The base current on the high voltage side of the transformer is:

Answer 1