Lightning induced voltage on an aerial wire above two-layer ground

This paper presents a time-domain method for the calculation of induced voltages on an aerial wire above a soil represented by two horizontal layers. Each layer is assumed to be homogeneous, isotropic, and having its own electrical parameters: resistivity, permittivity and permeability. The horizontal electric field at the surface of the top layer is calculated for an incident azimuthal magnetic field and used for the calculation of the induced voltage, using a methodology previously presented by the authors. A simple line configuration is used in order calculate the voltages induced by typical return-stroke waveforms. The results show that the two layers influence the induced voltage waveform. For the example considered, the induced voltage is initially influenced by the first layer but, as time goes by, it follows the voltage that would be induced if the earth was homogeneous and had the characteristics of the second layer.