Investigation of soil as a lossy dielectric

The authors present results of measurements and laboratory tests performed with several soil samples to investigate their dielectric and conduction characteristics in the predominant range of frequencies for transient phenomena in electric power systems. The effects of such factors as humidity and frequency variation on these characteristics are considered, and an analysis of the obtained data is presented. At constant frequency, an increase of humidity results in an increase of permittivity and a decrease of resistivity and affects the value of loss tangent. When frequency is increased, the permittivity and resistivity decrease significantly. The loss tangent presents a maximum at intermediate frequency values. It is remarkable that at higher frequencies this parameter shows values not much different from those at lower frequencies