Study of Overvoltages at the Extinguishing Coil Disconnection from Medium Voltage Networks in Stabilized Earthing Regime

Considering that in medium voltage networks with neutral treated by the extinguishing coil there are real difficulties of selective triggering of the line with single-phase defect, the paper presents a study of overvoltages that occur at single-phase faults in medium voltage networks with neutral treated with extinguishing coil, followed by the triggering of the extinguishing coil immediately after the stabilization of the grounding regime. The study is performed by simulating in the Simulink computer program a medium voltage network fed radially from a 110/20 kV transformer station. If the results of the study lead to the conclusion that overvoltages are not dangerous for installations, then for permanent grounding the deliberate disconnection of the extinguishing coil, and thus the transformation of the net neutral treatment from the neutral treated by the extinguishing beret into isolated neutral, will ensure selective triggering of the defective line.