Interaction of lightning-generated electromagnetic fields with overhead and underground cables

In this chapter, we present the general theory describing the interaction of an impinging electromagnetic field with transmission lines, with particular reference to lightning-induced voltages. The chapter presents the field-to-overhead transmission line models that have been proposed to describe the coupling of electromagnetic fields to transmission lines. The derived equations are then extended to deal with the presence of losses and multiple conductors, and expressions for the line parameters, including the ground impedance and admittance are presented. Solution methods in the frequency domain and in the time domain are also presented. In addition, application examples of lightning-induced voltages are presented, with special emphasis on the effect of ground losses. The chapter presents a theoretical framework for modelling the electromagnetic field interaction with a buried cable. Expressions for the line parameters are given and solution methods in the frequency domain and in the time domain are presented. Examples of lightning-induced currents and a comparison with experimental data obtained using triggered lightning are also included.