Chapter 7, Problem 7.14P

Equipment ratings for the five-bus power system shown in Figure 7.15 are as follows:

Generator G1:     50 MVA, 12kV,  $X"=0.2$ per unit

Generator G2: 100 MVA, 15 kV, $X"=0.2$ per unit

Transformer T1: 50 MVA, 10 kV $\text{Y}/138\text{kV}\text{Y,}$ $X=0.10$ per unit

Transformer T2: 100 MVA, 15 kV $\Delta /138\text{kV}\text{Y,}X=0.10$ per unit

Each 138-kV line: $X_1=40\Omega$

A three-phase short circuit occurs at bus 5, where the prefault voltage is 15 kV. Prefault load current is neglected. (a) Draw the positive-sequence reactance diagram in unit on a 100-MVA, 15-kV base in the zone of generator G2. Determine (b) the Thévenin equivalent at the fault, (c) the subtransient fault current in per unit and in kA rms, and (d) contributions to the fault from generator G2 and from transformer T2.