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

Document Type : Research Article

Authors

1 Arak University

2 Amirkabir University of Technology

Abstract

In this paper, different aspects of lossy soils including ionization, and frequency-dependence of electrical parameters of soils (dispersive soil) simultaneously on the grounding potential rise (GPR) of multiple vertical rods under lightning return strokes are investigated. In all analyses, an efficient modeling approach called improved multi-conductor transmission line (IMTL) is adopted. Based on the previously published papers, this modeling approach is in good agreement with full-wave methods.

In the case of single rod, IMTL-based numerical analyses show that when the two mentioned aspects, i.e., ionization and dispersion, are simultaneously,occurred, GPR is more decreased with respect to situations where only one aspect , i.e., either ionization or dispersion, is considered. This reduction is more pronounced for highly resistive soils, and fast-fronted lightning currents. In the case of multiple rods, however, it is placed between the GPRs of only-ionized and only-dispersive soils. Moreover, sensitivity analysis on the non-homogeneity effect in ionized and dispersive soils is carried out.

Since, the measurement of GPR at high frequencies is difficult, this motivates the authors to propose closed-form expressions for GPR of multiple rods. Hence, comprehensively predicting formulae for GPR of multiple rods versus parameters of lightning current, lossy soil and rod length are extracted. The predicted results are in excellent agreement with IMTL.

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