A contribution to the study of ground grids impulse impedande, based on field measurements

This paper presents a study about the impulse impedance of grounding grids based on experimental measurements performed within a testing field developed for this purpose. It considers an extensive number of measurement sets performed in grounding grids with different dimensions and topologies. The main goal is to evaluate an appropriate procedure to be employed during field measurements, as well as to verify the impulse impedance behavior in relation to low frequency ground resistance and ground grid topology. Field test results show a strong correlation among important quantities such as impulse factor, resistance and inductive reactance of an equivalent RL circuit, and the grids topology. These results may contribute to the development of a methodology, which aims to adequately estimate the impulse impedance of grounding grids as a function of the resistance measured at low frequencies and the grid topology.