(Solved): 4. The system shown below, reactances of a generator rated 100 MVA, 20 kV, are Xd"=X1=X ...

4. The system shown below, reactances of a generator rated 100 MVA, 20 $$\mathrm{kV}$$, are $${\mathrm{X}}_{\mathrm{d}}"={\mathrm{X}}_1={\mathrm{X}}_2=25\%$$ and $${\mathrm{X}}_0=5\%$$, the generator is connected to a $$??Y$$ transformer rated $$100\mathrm{MVA},20??230\mathrm{Y}\mathrm{kV}$$, with a reactance of $$10\%$$. The neutral of the transformer is solidly grounded. The terminal voltage of the generator is $$20\mathrm{kV}$$ when a single line-to-ground fault occurs on the open-circuited, high-voltage side (230 kV bus) of the transformer. Draw per unit equivalent circuit for the positive, negative and zero sequence equivalent circuits and connect them according to the fault description, then find the initial symmetrical RMS current in all phases of the generator in ampere. $$(10+20=30)$$