It has been well known for many years that grounding resistance has a current-dependent characteristic due to soil ionization. Moreover reinforced concrete poles should be treated as a kind of grounding electrode against lightning strokes. However, these characteristics were seldom taken into account for lightning-protection designs. If these characteristics are represented in EMTP models for lightning protection designs, the rationalization of the lightning protection designs for distribution lines is expected. In order to clarify transient behaviors of a system of a grounding electrode and a concrete pole, experiments were conducted with full-scale grounding systems. In this study, the paper described a composite model of a reinforced concrete pole and a grounding electrode for distribution lines and compared the calculated waveforms with measured waveforms of the experiments. The results show that it is necessary to take a current-dependent characteristic into account and treat concrete poles as a kind of grounding electrode.
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