$7\mathrm{.}10$ Recalculate the subtransient current through the breaker in Problem $7\mathrm{.}6$ if the genera$-$

tor is initially delivering rated MVA at $0\mathrm{.}80$ p$.$f$.$ lagging and at rated terminal voltage

$7\mathrm{.}6$ 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 Xd $1$:$5$ per unit, and

its time constants are T$00$

d $0$:$05,$ T$0$

d $1$:$0,$ and TA $0$:$10$ 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 gener$-$

ator 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