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Experimental Investigation on the Impulse-Current Distribution of Grounding Electrodes with Various Structures

When impulse currents are injected into grounding electrodes and dissipate in the earth, the axial current distribution of the grounding electrodes will change with different electrode structures. In order to analyze the distribution law, using Rogowski coil as a current sensor, impulse simulation experiment is designed and performed on the grounding electrodes with various structures. Basing on the principle of dimensional similarity, the experiments are carried out in a 5 m-diameter hemispherical sand pond. The impulse currents of 8/20 mus waveform are fed into a single horizontal grounding electrode, a star-shaped grounding electrode, a cross-shaped grounding electrode and vertical grounding electrode(s). The axial currents in the electrode branch conductors are measured accurately and the current wave curves at the measured points are also presented. The soil ionization around the electrodes has been taken into consideration in our tests. The data and graphs can help to verify and improve analytical models applied in grounding system and lightning protection design.