An improved transmission-line model of grounding system

This paper presents a time-domain transmission line model of grounding syst em, which includes the mutual electromagnetic coupling between the parts of the grounding structure and the influence of air-earth interface. The mode l can be used to simulate the transient behavior of the grounding system un der lightning strike. The simulation results are in good agreement with tha t of the model based on the solution of full Maxwell's equations [1], [2] a nd also with the measurements reported in [1]. The influence of different p arameters, such as the soil relative permittivity epsilon (r), the soil res istivity rho, and the conductivity and diameter of the conductor, on the tr ansient voltage distribution of the grounding system is investigated. It sh ows that, among the parameters investigated here, the soil resistivity is t he most important parameter that affects the transient response of bare bur ied conductors. The soil permittivity has very little influence on the tran sient response of the grounding system when the grounding system is buried in the soil with low resistivity, but have moderate influence in the soil w ith extremely high resistivity. The conductivity of the conductor and skin effect have practically no influence on the peak transient voltage of the g rounding system. Increase in conductor diameter tends to decrease the peak transient voltage. The model presented in this paper is simple, but suffici ently accurate and can be used easily in engineering practice. Since the mo del is in the time domain, it could be easily coupled to the other time-dom ain models of nonlinear surge-protection components.