Fundamentals of Coupling of Lightning Fields to Overhead Lines

Lightning can induce unwanted currents and voltages on overhead lines that can have a significant impact on power quality and calculating the overvoltages is essential to designing and optimizing lightning protection to minimize nefarious effects. Three complete coupling models that are based on the transmission line approximation have been proposed in the literature. The models have different forcing sources, different equivalent circuit models, and were presented at about 15-year intervals. Despite their differences, the three models have been shown to be fully equivalent. In this lecture, we derive the equivalent circuit and equations for one of the models using an intuitive approach, we compare the resulting model to the version derived from Maxwell's equations, and we give the differential equations and equivalent dritributed circuits for all three models.