Switching overvoltages are the main sources of disturbances in power plants. Switching overvoltages occur during the switching and/or switching of switching devices. This paper provides theoretical background on switching overvoltages, insulation coordination, ATP software package, Gaussian and Weibull distributions. It also describes the procedures for analytical and numerical calculation of voltage probability distributions. The paper presents a statistical analysis of switching overvoltages in the power system, using the Monte Carlo method and numerical simulations of overvoltage conditions using the ATP-EMTP software package. The analysis of the simulation results of different models explains the influence of the number and position of surge arresters on the probability of voltage magnitudes. The obtained results can help in the statistical method of insulation coordination. The data obtained by mathematical and numerical methods are compared. Based on the obtained results, it can be concluded that the Weibull distribution can predict the probabilities of overvoltage magnitudes.