A Method of Faulty Line Selection for the Flexible Grounding System Based on the Parallel Resistance Identification

Abstract

Aiming at the difficulty in selecting the fault lines when the high resistance grounding system of a distribution network, a method of faulty line selection for flexible grounding system based on parallel resistance identification is proposed. The relationship between each line's zero-sequence current and the bus's zero-sequence voltage are analyzed in detail after the parallel resistance was put into use, based on which an equivalent model with parallel resistance is established for each feeder. The characteristic differences between the faulty and sound feeders are reflected by deriving the parallel resistance parameters fitted to each feeder with the method of least squares. Faulty line selection criteria are formed by the feature that the fitted value of parallel resistance for which the faulty line is close to actual value and the sound line is much greater than the actual value. Simulation results of the MATLAB show that this method is suitable for the ground faults with a transition resistance less than 3000 ohms. It has rather high reliability under the different faulty conditions.