Current distribution in soil due to lightning impulse discharge from indirect lightning

Abstract

The damages due to the lightning are mostly severe where the lightning causing them are divided into two types: direct lightning and indirect lightning. Sensitive facilities such as data centres, communication towers and green energy sources like solar and wind turbines suffer a lot of danger from indirect lightning in the form of ground potential rise (GPR) and lightning electromagnetic pulse coupling (LEMPC). Most research focused on the effect of direct lightning strike to facility while little attention is given to the effect of an indirect lightning strike. This research looked into the characteristic effects of indirect lightning current propagation on various soil and how the soil properties affect the current distribution to nearby areas. The research was conducted using a laboratory scale lightning discharge replica on soil and the results are supported with simulations and numerical calculations using NI Multisim and COMSOL Multiphysics (AC / DC) module. The results from the research show that the current distribution in soil due to lightning discharge is strongly dependent on the conductivity of the soil. This property of the soil was however not a constant. It is a time varying property relating to the soil moisture, pH and available nutrients. A soil model was derived to be of the complex-impedance (Z = R+L // C) type having a linear section and non-linear section dependent on time. The results produced are extensive. Limited computational power imposed some limitation on the sample size in this study, however. The work can be improved if more powerful computers become available.