Applications of time-domain numerical electromagnetic code to lightning surge analysis

Recently, applications of 3-D numerical electromagnetic analysis have been increasing either for lightning electromagnetic impulse (LEMP) studies or lightning surge analyses on transmission and distribution lines. This paper is mainly concerned with the use of time- and frequency-domain codes for electromagnetic analysis of lightning surges. The thin-wire in time-domain (TWTD) code and numerical electromagnetic code (NEC-2) in the frequency domain based on the method of moments are chosen for comparative studies. The accuracy of TWTD code in the analysis of lightning surge characteristics of a double-circuit transmission tower is first investigated by comparing the computed results with the measured results on a reduced-scale tower model, computed results by NEC-2 on a full-scale tower model, and those computed by electromagnetic transients program. In the latter part of the paper, a switch model is combined with the TWTD code, and its applicability in analyzing the lightning surge characteristics of a transmission tower equipped with a surge arrester or in analyzing lightning-induced voltage on an overhead line is demonstrated.