Resistance based Mitigation of Very Fast Transient Over Voltages in Gas Insulated Substations

Abstract

this paper presents mitigation technique of Very fast Transient Over Voltages(VFTOs) in Gas Insulated Switch gear based substations. VFTOs in GIS based substations are due to switching operation of disconnector switches, circuit breakers and isolators and so on. If VFTOs are not mitigated it leads to decrease in insulation levels of transformers and other equipment and break down and hence initiation of partial discharge. In this work to reduce these VFTOs, disconnector switches are rearranged by adding additional resistance as mitigating device. Four Substations with different voltage ratings (765KV, 1000KV, 1200KV and 1500KV) are chosen to check effectiveness of resistor as mitigating device in reducing VFTOs. Optimized value of resistor is chosen by examining VFTOs in four substations with different values of resistances. Substation is modelled and results are presented in MATLAB/SIMULINK.

Keywords-Gas Insulated Switch Gear, SF₆ circuit breaker, VFTO, sim power systems