Investigation of Impulse Discharges in Two-Layer Wet and Dry Soil Sample

Soil ionization phenomena in dry soils are considered the main cause of the observed nonlinear behavior under impulse voltages, the very high resistivity of the dry soil falling dramatically at the instant of breakdown. In this study, a two-layer columnar test sample composed of a glass bubble material was used to investigate the associated ionization and breakdown processes. Three voltage dividers were utilized to measure the applied lightning voltage and intermediate voltages at two probes located at fixed heights in the sample. A current transformer was used to measure the current flowing through the sample. When the voltage is high enough and after a certain delay time, current flow from the active electrode was detected by the current transformer, but the measured applied voltage did…