Question

The synchronous generator in Figure 7.3 is operating at rated MVA, 0.95 p.f.

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.

Answer 1

a) $If = \frac{Vf}{2KK}$

= i0.08Pu

b) $Ig = -j7 Pu$

c) $Im = - j0.08 Pu$