A simplified method for calculating the impedance of vertical grounding electrodes buried in a horizontally stratified multilayer ground

The reliability and availability of the electric power transmission system is severely affected by lightning. In Brazil, roughly 65% of the overhead transmission lines outages are due to lightning. The grounding impedance of transmission line towers plays an important role in the lightning performance of the lines. In this context, this paper proposes an alternative and simple methodology to calculate the transient voltage response of a grounding vertical electrode buried in a multilayer horizontally stratified ground. The grounding electrode is modeled as a transmission line and the proposed approach deals with single wire grounding electrodes. Comparisons with other methodology are presented and an application example is used to demonstrate the proposed methodology usefulness. The simulation results indicate some advantages of deep vertical electrodes when compared to horizontal conductors for the conditions of a second layer with lower resistivity values than the first layer. This is expected when dealing with low frequencies phenomena and the simulations results extends this conclusion to a high frequency range (500 kHz).