Frequency dependence of soil parameters: The influence on the lightning performance of transmission lines

The impact of the frequency dependence of soil parameters on the lightning response of transmission lines was assessed by simulation, taking an existing 138-kV line as reference. This can be important for overvoltages experienced across insulators due to lightning strikes, in particular of first strokes and soil resistivity above 300 Ωm. The effect causes a percentage decrease of the backflashover rate expected under the assumption of constant soil parameters of around 8%, 20% and 25% for values of soil resistivity of 300, 1000 and 2000 Ωm.