Document Type : Research Article
In this paper, with the use of adaptive-network-based fuzzy inference systems (ANFIS), closed-form expression for lightning-induced voltage of single-conductor overhead lines terminated with lightning arresters (overvoltage) is presented. The overhead line is stroked directly by lightning stroke. The lightning arresters are also grounded via two kinds of grounding systems namely vertical electrode and horizontal grid. Prior to creating the expression, at first a number of input-output pairs (inputs are resistivity of soil, overhead line height and electrode length while the output is the overvoltage across the arrester) are computed based on the exact models reported in the published literatures for the training process. Once the ANFIS algorithm is converged, the created simple expression can be easily used for efficient computation of overvoltage in soils with constant electrical parameters under arbitrarily-valued inputs which are different from samples selected in the training process. This simple expression can be easily used in dispersive soils and horizontally two-layered soils as well. To this end, the created ANFIS-based expression is integrated with equivalent resistivity approximations which leads to inclusion of the two effects separately and simultaneously in such complex soils. Evidently, this expression can be approximately used for three-conductor overhead lines which is of importance in practical point of view.