A 1000-MVA, 20-kV, 60-Hz, three-phase generator is connected through a 1000-MVA, 20-kV, /345-kV, Y transformer to a

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.  

Transcribed Image Text:

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