An Experimental Study of Surge Characteristics of a Distribution Line Using a Reduced-Scale Model

Abstract

Lightning-related overvoltages on 6.6-kV overhead distribution lines can roughly be classified into the two types: overvoltages induced by a nearby lightning stroke and overvoltages due to a direct lightning stroke to the distribution line. Protection measures against the former, which is commonly called lightning-induced overvoltages, have been taken and can be considered as completed. Regarding the latter, recent experimental studies have revealed that protection against a direct lightning hit is possible by applying appropriate countermeasures. Studies of such countermeasures are now carried out by digital simulations using the EMTP (Electro-Magnetic Transients Program), and thus components of a distribution line must be modeled appropriately in the EMTP for accurate simulations.This paper presents surge characteristics of a distribution line obtained by experiments using a reduced-scale distribution line model. The reduced-scale model includes a reinforced concrete pole, a ground wire, phase wires, a grounding lead conductor installed along the pole, and a lightning channel. Unlike preceding studies, the surge impedance of a reinforced concrete pole is measured considering the effects of a ground wire and phase wires. Voltages at various positions of the distribution line model have been measured with varying the wavefront time of the injected current simulating a lightning stroke and also varying the grounding resistance of the pole, and their effects are examined.