Insulation risk assessment of controlled switching considering pre-strike voltage and line trapped charge

Abstract

In this study, a method is presented for implanting controlled switching taking into account simultaneously the exact values of trapped charge and pre-strike voltage when Circuit Breaker (CB) contacts are approaching each other. This approach is implemented in the EMTP/ATPDraw environment using Transient Analysis of Control Systems routine. By presenting a new approach, the proposed method determines the optimum closing point for CB contacts without imposing any limitation on lineside fluctuations. In order to perform statistical switching, the presented method models the uncertainties of controller circuit, the mechanical circuit of CB, and trapped charge voltage. Unlike the conventional approaches in which the statistical parameters were selected by default, in the presented statistical switching these parameters are estimated based on CB parameters. Furthermore, the presented method is used to calculate the insulation risk caused by controlled switching overvoltage. Simulation results show the accurate and efficient performance of the proposed controlled switching approach in significantly decreasing the risk and the maximum overvoltage created along the line, compared to the conventional CB. So that, insulation risk has decreased to zero and the maximum overvoltage created along the line has decreased to 46%.