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

$20-$kV D$/345-$kV Y transformer to a $345-$kV circuit breaker and a $345-$kV transmission

line. The generator reactances are X

$00$

d

$0$:$17,$ X

$0$

d

$0$:$30,$ and X

$1$:$5$ per unit, and

its time constants are T

$00$

d

$0$:$05,$ T

$0$

d

$1$:$0,$ and T

A

d

$0$:$10$ s$.$ The transformer series

reactance is $0\mathrm{.}10$ 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 rated terminal voltage and at no$-$load. The breaker interrupts the

fault $3$ cycles after fault inception. Determine $($a$)$ the subtransient current through

the breaker in per$-$unit and in kA rms; and $($b$)$ the rms asymmetrical fault current the

breaker interrupts, assuming maximum dc o$$set$.$ Neglect the e$$ect of the transformer

on the time constants.