GPR of Multiple Vertical Rods under Lightning Strokes Considering Ionization, Dispersion, and Non-Homogeneity of Lossy Soils

In this paper, the effects of ionization and dispersion of a lossy soil on the Grounding Potential Rise (GPR) of buried multiple vertical rods under lightning return strokes are simultaneously studied. In all studies, an efficient modeling method, called improved Multiconductor Transmission Line, is adopted. In the case of a single rod, it is shown that the simultaneous occurrence of soil ionization and dispersion causes further reduction in the value of GPR as compared to the case where each phenomenon takes place separately. The amount of reduction is further accentuated when treating highly resistive soils and fast-fronted lightning currents. In the case of multiple rods, however, the value of GPR in both ionized and dispersed soil lies between those of the only-ionized and only-dispersive soils. Besides, the sensitivity analysis of the non-homogeneity effect in ionized and dispersive soils provides a comprehensive platform to study the soil dependence of the GPR of buried rods in a multi-layer soil. Finally, closed-form expressions are proposed that can accurately predict the value of GPR for both single and multiple rods buried in a dispersive and ionized lossy soil when subjected to a lightning current waveform.