EMP-coupling to twisted-wire cables

An EMP (electromagnetic pulse) coupling to twisted-wire pair (TWP) cables above a ground reference plane is considered. The high-altitude EMP is represented by a plane wave. TWP cable is simulated in the frequency domain as a multiconductor uniform line excited by non-uniform electromagnetic fields. EMP-induced effects are computed by using an efficient matrix procedure based on the transmission line model (TLM). The transient waveforms for any terminal load conditions are obtained by an inverse discrete Fourier transformation. The theoretical procedure is applied for evaluating the EMP-induced effects on a TWP cable for different electric and geometric configurations. The results obtained by the procedure are compared with those computed for a parallel wire-line. The transient wire-to-ground voltages are very similar for TWP and parallel wire configurations. The wire-to-wire voltages and wire currents depend on the polarization and the incidence angles of the EMP plane-wave.