Case Study of the Lightning Performance of a 230 kV Transmission Line

This paper presents a statistical lightning performance study conducted for a North American 230 kV transmission line in order to investigate a shielding failure flashover that caused equipment damages. The study is performed in IEEE Flash program by using actual design and field-measured data. The investigation results are presented in terms of estimated total flashover (back-flash and shielding failure flash) rates and corresponding critical currents. The total flashover rates for the entire transmission line are also computed from the lightning performance results of individual tower structures and connected conductors. Moreover, a sensitivity analysis is furnished in order to assess the influence of tower footing resistance on the results. The obtained results indicate that the probability of occurrence of a shielding failure on the line is low. However, the utility should install lightning arrester at least at the substation entrances in order to mitigate the likelihood of future equipment damage.