An approach to the analysis of the electromagnetic interferences radiated by metallic grids struck by lightning

In this paper an approach to the numerical analysis of the electromagnetic interference (EMI) radiated by metallic grids, like Faraday cages, hit by a lightning stroke is proposed. This approach is based on a hybrid differential-integral mathematical formulation in which a finite-difference time-domain scheme is used to evaluate the current density distribution inside the conductors, while the Kirchhoff's integral expressions are used for the computation of the transient electric and magnetic fields generated by the current flow into the grid. The introduction of a suitable scalar potential defined on the surface of the conductor allows to determine a complete set of boundary conditions for the problem of the magnetic diffusion of the current into the conductor and to reduce the region to be numerically treated by the differential formulation to the only conducting materials. Examples of application of the method to the numerical analysis of the EMI radiated by a Faraday cage struck by lightning are given.