Method of equal probability overvoltages for calculating risk of failure of power transmission lines

The author presents a generalised numerical method for calculating the risk of failure of power transmission lines due to switching overvoltages. The method incorporates the influence of overvoltage profile and differences in breakdown properties of insulation along the line on the risk of failure, irrespective of their probability distribution laws. The risk is calculated for several overvoltage probability distribution laws and line insulation levels. The influence of the overvoltage distribution along the line, i.e. overvoltage profile, on the risk of failure is considered for overvoltages obtained by calculations, as well as for overvoltages obtained by measurements on a specific transmission line. If the breakdown properties of insulation are given as a function of the wave front duration, it is possible by this method to incorporate into the calculations the influence of the wave front duration along the line on the risk of failure