Development of a computer program for the analysis of alternatives of insulation coordination in high-voltage substations

A computer program developed in Matlab® to compute the insulation coordination taking into account different proposed improvements is presented. The program considers special considerations of earth fault, the load rejection constants, selection of surge arresters, proper calculation of the Shielding Failure Flashover Rate (SFFOR) and Back Flashover Rate (BFR). The goal of applying this improvements in the insulation coordination scheme is to update the application procedure guide granted by IEC 60071-2, looking for better results according to the local and modern issues. The improvements will increase the safety margins of the protected installations, with the aim of obtaining better results in the operation of the electrical network. Four aspects were analysed on this study: the location of the ground wire respect to the phases, the values of constants for short-circuit and load-rejection for the Chilean electrical system, the distance between surge arresters and devices, and the influence of soil resistivity in the overvoltage values.