Effective length study of grounding electrod reached by lightning based on Transmission Line modelling Method

This paper presents a study about the effective length of a horizontal grounding electrode used to dissipate electrical current to the earth proceeding from a lightning surge. The work discusses the influence of the soil parameters in the scattering process considering fasts and slow wave shapes. Initially an introduction about the problem is made, with a brief description about the effective length concepts. An algorithm based on the Transmission Line Modeling Method in one dimension (TLM-1D), taking into account the soil ionization phenomenon, was developed in order to evaluate the transitory behavior of the grounding. The simulation results show that a significant part of the electrode is not effectively used for scattering the surge current to the soil and that the effective length of the conductor is dependent mainly on the soil resistivity and the wave shape.