The lightning protection effects of power transmission lines are related to the impulse characteristics of grounding systems of transmission-line towers. The influences of several main factors on impulse grounding properties are systematically analyzed by simulation experiments according to the simulation theory in this study. Soil resistivity was changed in the region between 100 to 5103 /spl Omega//spl middot/m. The influential regularities of different parameters on impulse grounding resistance and impulse coefficient of different grounding devices for transmission lines in high resistivity region are discussed. By analyzing the experimental results, the authors conclude that the structure of grounding systems should be selected according to soil resistivity, geological structure and technical economy analysis. The fitting calculating formulae of impulse coefficients and power frequency grounding resistances of different grounding systems are acquired. The simulation results are in good agreement with those of field experiments in the literature.
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