An analysis on the frequency-dependent grounding impedance and current distribution of the counterpoise in two layered soil structure

초록

The grounding sustem performance against high frequency fault current is defined by the grounding impedance. A number of studies have reported that grounding system performance is reduced due to the increase of the grounding impedance with the increase of the fault current frequency. As seen in this paper, the frequency-dependent grounding impedance of the couterpoise installed in a two-layerd soil section depends on the length of the grounding electrode; the current injection point is measured and analyzed based on the rate of the current dispersed on the counterpoise. As a result, most of the ground currnet aboce the frequency of 100kHz are dispersed into the soil near the current injection point and the hgh frequency grounding impedacne of long counterpoise is transformed into that of a short counterpoise. The high frequency grounding impedance measured at the low soil-resistivity end of the counterpoise buried in the two-layer soil structure is mcuh lower than that found at the high soil resistivity end.