A 200 MVA, 20 kV, 60 Hz, three-phase synchronous generator is connected through a 200 MVA, 20/138 kV, A-Y transformer to a 1 38 kV transmission line. The generator reactances to the machine's own base are; xs-1.40 The initial transient dc component in this machine averages 50 percent of the initial symmetrical ac component. The transformer's series reactance is 0.10 pu, and the resistance of both the generator and the transformer may be ignored. Assume that a symmetrical three-phase fault occurs on the 138 kV transmission line near to the point where it is the transformer. 1. What is the ac component of current in this generator the instant after the fault occurs? 2. What is the total current (ac plus dc) flowing in the generator right after the fault occurs?

A 200 MVA, 20 kV, 60 Hz, three-phase
synchronous generator is connected through
a 200 MVA, 20/138 kV, A-Y transformer to a
1 38 kV transmission line. The generator
reactances to the machine's own base
are; xs-1.40
The initial transient dc component in this
machine averages 50 percent of the initial
symmetrical ac component. The
transformer's series reactance is 0.10 pu,
and the resistance of both the generator and
the transformer may be ignored. Assume
that a symmetrical three-phase fault occurs
on the 138 kV transmission line near to the
point where it is the transformer.
1. What is the ac component of current in
this generator the instant after the
fault occurs?
2. What is the total current (ac plus dc)
flowing in the generator right after the
fault occurs?
3. What is the transient fault current If in
this fault?
4. What is the steady-state fault current If
in this fault?