UNSYMMETRICAL FAULT CALCULATIONS – PART – 12 PART – 12 – SINGLE LINE TO GROUND FAULT

In a balanced three phase system negative and zero sequence currents are zero.

In a three phase, four wire system the magnitude sequence current is one-third of the current in the neutral.

The neutral is not earthed the zero sequence impedance is infinity, hence the fault current is zero.

The most common type of three phase fault is the single line to ground fault (70%).

ASSUMPTIONS

1. The impedance of the fault is zero.

2. Load currents are neglected.

3. The generated e.m.f. the system is of positive sequence only.