The Behavior of Earthing Impedance and StepPotential For Surge Currents

For an effective earthing system, the resistance/impedance of the earthing system should be held at the lowest possible level. In this study, a surge generator, which can inject a 2-kV signal of 1.2/50 μs waveform or 1 kA impulse current waveform of 8/20 μs, was constructed to investigate the impedance of single rod earthing system. The resistivity of the soil at the selected location varies from 300 Ωm - 1700 Ωm. By using the fall of the potential method, it was observed that the impedance of single rod system varies from 900 Ω at 1 m to 70 Ω with the distance of 2-5 m. The earthing resistance of the same system was found to be 285 Ω, which is higher than the impedance.