Transient Electromagnetic Field Coupling to Long Shielded Cables

A model is presented for determining the transient currents and voltages induced within long shielded coaxial cables by an impinging electromagnetic pulse (EMP). The transmission-line theory is applied to establish the differential equations describing the behavior of the cables in the presence of a uniform plane traveling wave. At first, induced sheath currents are calculated taking into account different coupling modes. Then, internal voltages and currents are computed via the surface transfer impedance of cable shields for one and multilayer outer conductors. Comparison with measurements show the validity of the proposed method. The computer codes developed for this purpose have been found to be a very useful tool for the optimization of shielded transmission cables.