Laboratory investigation of impulse characteristics of transmission tower grounding devices

Reducing grounding resistance of a transmission tower grounding device is an important method to improve performance of transmission lines against lightning. Principles of impulse characteristics of grounding devices were discussed. Impulse experiments using grounding device models were systematically performed to analyze the influence of different factors on the impulse characteristics of grounding devices. During the experiments, soil resistivity was changed in the range of 100 to 5103 (omega).m. Effects of different parameters on impulse grounding resistance and impulse coefficients of different transmission tower grounding devices were discussed. Formulae to calculate impulse coefficients and power frequency grounding resistance of different grounding devices were obtained.