Fault location analysis of ungrounded distribution system based on residual voltage distribution

This paper proposes a new method for determining the location of single-phase-to-ground faults of ungrounded distribution systems based on residual voltage distribution. The possible faulted line segment and fault location are determined by comparing the phase angles of faulted phase voltages against a faulted phase reference angle, and the faulted phase voltages are determined as the difference between the fault caused residual voltage of all phases and the shunt caused residual voltage of un-faulted phases. The method determines the fault location solely based on the voltages and currents measured during the fault, and associated series impedance and shunt impedances of line segments. It does not require any measurements or information for the load demands and prefault conditions. Numerical examples are given to demonstrate the effectiveness of the proposed method.