CALCULATING LIGHTNING-INDUCED OVERVOLTAGES IN POWER-LINES - A COMPARISON OF 2 COUPLING MODELS

A comparison is made between two coupling models frequently used to es timate the lightning-induced overvoltages in power lines. The first mo del was introduced by Rusck [1] and the second model by Agrawal, Price , and Gurbaxani [2]. In the nomenclature adopted in this paper, the fi rst model is referred to as the ''Rusck model'' and the second as the ''Wave Antenna Model.'' The transmission line equations of the Rusck m odel can be written in such a way that the forcing term in the equatio ns is the horizontal electric field. The results show that the Rusck m odel is incomplete. It takes into account the portion of the horizonta l electric field generated by the gradient of the scalar potential but neglects the contribution from the vector potential. This defect in t he Rusck model makes it source-dependent. That is, the Rusck model can give accurate results only when the spatial location of the source th at generates the electromagnetic field is such that the contribution o f the vector potential to the horizontal field is either zero or can b e neglected. Under such circumstances the Rusck model and the Wave Ant enna Model are described by the same transmission line equations, and the results predicted by the two models are identical.