An Empirical Formula for the Surge Impedance of a Grounding Conductor along a Reinforced Concrete Pole in a Distribution Line

The contribution of the surge characteristic of a grounding vertical conductor to an induced voltage across an insulator becomes prominent if the lightning current has a steep front. The present paper derives an empirical formula of a vertical grounding conductor including the effect of a reinforced concrete pole close to the vertical grounding conductor based on a measure d result on a reduced-scale model. This empirical formula is expressed in the form of a logarithmical function considering a deviation of the self-surge impedance of the grounding conductor along the reinforced concrete pole from that of a single grounding conductor. The developed formula agrees well with measured results.