Numerical electromagnetic field analysis of tower surge response

Tower surge responses are computed by the numerical electromagnetic code. The code used in this paper is not the one based on the circuit theory such as the Electro-Magnetic Transients Program (EMTP), but the one that solves the electric field equations directly by the moment method. The accuracy of this method is shown to be satisfactory by comparison with experimental results that were carried out on an actual UHV tower as well as reduced-scale models. And then by using this method, the influences of tower elements such as slant elements, horizontal elements and crossarms on the tower surge characteristics are investigated. In addition, the surge impedance of a full-sized tower hit directly by a lightning stroke is discussed.