3 A 3-phase 75MVA 08p.f. (lagging) 11.8kV star-connected alternator having its star point solidly earthed supplies a feeder. The relevant per-unit (p.u.)* impedances, based on the rated phase voltage and phase current of the alternator are as follows: Generator, ZG Feeder, ZF Positive sequence impedance (p.u.) j1.70 j0.10 Negative sequence impedance (p.u.) j0.18 j0.10 Zero sequence impedance (p.u.) j0.12 j0.30 Determine the fault current and the line-to-neutral voltages at the generator terminals for a one-line-to-earth fault occurring at the distant end of the feeder. The generator e.m.f. per phase is of positive sequence only and is equal to the rated voltage per phase. The positive, negative and zero sequence networks are shown in Figs. 4.27(c), (d) and (e). ERS (Vrs)+ + IR+ZG+ = 0 = (Vrs)- + IR-ZG- 0 = (Vrs) + IROZGO b GERS Zo ZF R PERS ERS ZF Y (a)