Abstract: An equivalent circuit method was presented to calculate lightning-induced magnetic fields in a metallic structure with non-ferromagnetic plates. With this method, thin plates in the structure were divided into tangential elements. According to the skin effect, a double exponential equation was used to simulate the current distribution across the thickness. By the transformation of electric field integral equation, the plates were modeled as interconnected and coupled circuit. By combining the equivalent circuit model of plate and columns, the current distribution on the metallic structure were then solved with a circuit analysis technique. The resultant magnetic field was calculated with the Biot-Savart law. The proposed approach was compared with the numerical method of boundary element method (BEM) and validated by an experiment conducted in the lab. A good agreement among these results was found. Finally the proposed method was used to evaluate the lightning-induced magnetic field in a building equipped with plates. The shielding effect of plates was analyzed.

Key words: lightning-induced magnetic field, non-ferromagnetic plate, current density, equivalent circuit model