Estimating locations of single-phase-to-ground faults of ungrounded distribution systems

This paper proposes a new method for determining single-phase-to-ground fault locations of ungrounded distribution systems based on the measurements collected from the feeder breakers and intelligent switches during the fault. The method first narrows down the possible faulted area into a specific feeder section based on the reactive power factors of residual powers determined for the breakers and switches. Then the power consumption of each individual load in the faulted section is determined based on measurements at the boundaries of the section, and load profiles for each individual load. The possible faulted line segment is determined using a forward sweep scheme to test a sign change of faulted phase voltages on terminal buses of line segments, and the possible fault point is determined by finding a location along the faulted segment having a zero voltage on the faulted phase. Numerical examples are given to demonstrate the effectiveness of proposed method.