Wave Propagation Speed and Equivalent Impedance of Dielectric-Coated Conductor Representing Lightning Return-Stroke Channel

In electromagnetic models of lightning return stroke, dielectric coating of channel-representing conductor is used to adjust the current wave propagation speed. In this letter, we examine dependences of both the speed and channel equivalent impedance on the electric permittivity and magnetic permeability of such coating. With increasing the permeability, the propagation speed of current wave decreases and the equivalent impedance increases significantly. In contrast, these parameters are not much influenced by the increase of permittivity. The reason for the difference has been explained in terms of the transmission-line theory.