EMTP analysis of the lightning performance of a HV transmission line

An accurate analysis of the lightning performance of a HV transmission line using the EMTP program is presented. By means of simulation using a digital model developed within the ATP-EMTP program with its MODELS-feature, the performance of a 110 kV unshielded overhead line under the influence of a direct lightning stroke is analysed. The simulation includes an adequate model of the transmission line, while also taking account of other factors such as the frequency dependence of the line parameters, models of wooden-porcelain insulation, wooden, and metallic towers and grounding systems including their impulse resistance characteristics. An impulse corona model (described elsewhere) is used, which, together with an adequate presentation of the flashover mechanism appropriate to air/porcelain insulation, allows one not only to predict the crest value of the overvoltages throughout the line, but also to assess accurately the real impact on the line fittings and substation equipment of the lightning surge travelling over the line. All the models are thoroughly verified by an extensive comparison of the simulated results with experiments by previous authors. Practical recommendations based on the simulations are made for an improvement in the lightning performance of a typical 110 kV transmission line.