Surge Impedances of Concrete Pole and Grounding Lead Wire in Distribution Line by a Scale Model Technique

Power apparatus in overhead distribution lines is set up on a concrete pole, and the impedance of a grounding lead wire can not be ignored. Therefore, it is important to know the surge impedances of the concrete pole and the grounding lead wire in the distribution lines for accurate lightning surge analyses. A scale model technique is very convenient to carry out an experimental study. Thus, the surge impedances are measured by an experiment on a reduced scale-model. Measured results lead to the following conclusions.(1) The surge impedance of the concrete pole alone and the grounding lead wire alone are 244 and 477 ohms, respectively.(2) The surge characteristic of the concrete pole is equivalent to that of a metallic pipe.(3) The surge impedance of the grounding lead wire to be along the concrete pole is significantly reduced as the location of the grounding lead wire becomes closer to the concrete pole.Moreover, this paper describes the reduction effect of a distribution surge arrester voltage by using the concrete pole as a grounding lead wire.