Abstract- This paper presents a circuit approach to compute the transient current distributions induced by a direct lightning on a metal structure such as oil containers in presence of a non-linear ground impedance. The metal structure is simulated by means of an equivalent network formed by resistances, capacitances and inductances having all the branches coupled to each other. A non-linear current-dependent electrical model, function of the electrode shape and the ground resistivity, represents the ionization phenomena in the soil. The analysis of the equivalent lumped-constants network is carried out by means of SPICE.
The influence of the non-linear ground impedance upon the distribution of the currents is put in evidence. The transient responses and the current distributions due to the stroke on a point of the structure are reported.