Power System Analysis

A dead earth fault occurs on one conductor of a 3-phase cable supplied by a 5000 kVA, 3-phase generator with earthed neutral. The sequence impedances of the alternator are given by Z1=(0.4+j4)ohm; Z2=(0.3+j0.6)ohm and Z0=(0+j0.45)ohm per phase. The sequence impedance of the line up to the point of fault are (0.2+j0.3)ohm, (0.2+j0.3)ohm, (0.2+j0.3)ohm and (3+j1)ohm. Find the fault current and the sequence components of the fault current. Also find the line to earth voltages on the in faulted lines. The generator line voltage is 6.6kV.

A generator supplies 1.0 p.u. power to an infinite bus as shown in the figure. The terminal voltage and infinite bus voltage are 1.0 p.u.All the reactances are on a common base. Determine steady state stability limit:

1. When both lines are in.
2. When one line is switched off.