Measurement and analysis of impulse grounding impedance of tower grounding device subjected to artificial lightning M‐component

The impulse grounding impedance of tower grounding device is one of the important factors in the lightning protection evaluation of transmission line. The impulse characteristic test of the actual tower grounding device under lightning was rarely carried out due to the limitation of the test conditions. With the help of Guangzhou Field Experiment Site for Lightning Research and Testing, the artificial lightning characteristic test of the true tower grounding device was carried out. This paper presented partial observation experimental results and related analysis of the impulse grounding impedance of tower grounding device subjected to artificial lightning M‐component. A calculation model of the tower grounding device subjected to lightning M‐component was established. The changes of the surface soil resistivity under the action of rainwater were taken into account in the calculation. The test data and calculation results of the tower grounding device under the impact of the artificial lightning M‐component had achieved good agreement. The non‐linear ionization of the soil around the tower grounding device can be ignored, and the real impulse grounding impedance was very close to the DC grounding resistance or power frequency grounding impedance, when the tower grounding device in the experiment was subjected to lightning current M‐component. The purpose of this paper is to measure and analysis the impulse grounding impedance of grounding grid subjected to artificial lightning M‐component. After comprehensively considering the effect of rainwater on the reduction of surface soil resistivity, the measured results of the ground potential rise waveform of the grounding grid in this experiment were well restored. The real impulse grounding impedance of the tower grounding device were very close to the DC grounding resistance or power frequency grounding impedance due to low amplitude and very small steepness of lightning current M‐component. The experiment concluded that the nonlinear ionization of the surrounding soil can be ignored, when the grounding grid in the test was under the action of the lightning current M‐component.