Observations on the Adequacy of Transmission Line Coupling Models for Long Overhead Cables

This paper reviews a technique for determining the response of a transmission line (TL) excited by an incident electromagnetic (EM) field. The Telegrapher’s equations are introduced first and a method of solution related to an EM scattering analysis is presented. It is shown that it is important to be consistent in treating the excitation sources on the line. Either the general high-frequency representations of the sources, or the low-frequency approximations may be used, but not a mixture of the two. A comparison of the TL solution with that provided by an integral equation for the same line geometry is then presented. It is apparent that for the particular example chosen for this paper, the TL model fails to provide an accurate solution. As a result, modifications first suggested by Prof. Degaque for treating the ends (or “risers”) of the line as additional transmission lines connected to the main line have been included in the coupling model. This provides results that agree very well with the integral equation solution.