UNSYMMETRICAL FAULT CALCULATIONS – PART – 27 – DOUBLE LINE-TO-GROUND FAULT - PROBLEM

Two generators A and B are of rating 50 MVA, 11kV, three-phase and 50 Hz are connected in parallel and supply a substation feeder.

Generator A and B positive, negative and zero sequence impedances are Z1= j0.6 ohms, Z2 = j0.4 ohms, Z0 = 0.2 ohms and neutral impedance Zn = j0.1 ohms.

Feeder positive, negative and zero sequence impedances are

Z1 = Z2 = (0.4 + j0.7) ohms, Z0 = (0.7 + j3.0) ohms.
If fault involves in Y and B phases, calculate the fault current.