Answer to Question #158943 in Electrical Engineering for Mina malik

Question

The synchronous generator in Figure 7.3 is operating at rated MVA, 0.95 pf. lagging and at 5% above rated voltage when a bolted three-phase short cir- cuit occurs at bus 1. Calculate the per-unit values of (a) subtransient fault current; (b) subtransient generator and motor currents, neglecting prefault current; and (c) subtransient generator and motor currents including prefault current. FIGURE 7.3 2 Single-line diagram ofa (G synchronous generator feeding a synchronous 100 MVA 138 kVY/13.8 kV Δ X = 0.10 100 MVA 100 MVA 100 MVA 13.8 kV X"0.20 motor 13.8 kV 13.8 kV A/138 kVY X"0.15 X0.10

Answer 1

A) $If = \frac{Eg}{xeg}$

$= \frac{1}{0.375}$

= 2.66

B) Im = 69.79 A

c) 161 A