Segment location for single-phase-to-ground fault in neutral non-effectively grounded system based on distributed electric-field measurement

摘要

Based on the analysis of the electric-field information distributing along the transmission lines, this paper proposes a new segment location scheme for single-phase-to-ground fault (SPG) in the neutral non-effectively grounded system. Through theoretical derivation, an optimum measuring position can be found at which the electric-field component has the proportional relation with zero-sequence voltage on the corresponding mapping location of transmission line. Then it can actualize the non-contacted and distributed zero-sequence voltages measurement with the remarkable advantages of safety and convenience. In view of there being the transient changes of the electric field at the moment of failure, as well as there being great difference between the electric-field measured at the upstream and downstream segments adjacent to the grounded point, the transient electricfield waveforms of different measuring points along the lines are obtained and the similarity degrees of waveforms from each adjacent measuring points are quantified based on Dynamic Time Warping (DTW) algorithm. DTW algorithm can highlight and quantify the above-mentioned differences and weaken the requirement of synchronous measurement at multiple points. Several simulation cases are designed with different fault conditions and the analysis results are compared to verify the effectiveness and sensitivity of the proposed method.