In this paper, an efficient hybrid method is proposed for transient analysis of an overhead line equipped with a grounded arrester. The proposed method adopts a nonlinear equivalent circuit consisting of linear and nonlinear parts respectively associated with the overhead line and the arrester. In the first part of the paper, an intelligent model based on qualitative concepts in electromagnetics is proposed for derivation of the linear part. With the use of this qualitative model, the behavior of the linear part is first extracted as simple and unchanged membership functions, and effects of parameters of the problem, that is, the height of the overhead line and the electrical parameters of the ground, are then extracted as simple curves so that the linear part based on the qualitative model is efficiently computed in the frequency domain. The qualitative model, in contrast with the conventional numerical methods, is very efficient, and in comparison with the approximate ones, is broad band. In the second part of the paper, with the aid of an efficient optimization algorithm, called intelligent water drop algorithm (IWD), the lightning overvoltage across the arrester is efficiently computed.
