Coupling of transient electromagnetic fields radiated by ESD to aerial coaxial cables

A Transmission Line model of coupling is developed for determining the transient currents and voltages induced within aerial shielded coaxial cables by an impinging electromagnetic pulse generated by an Electrostatic Discharge (ESD) event. 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 coupling in aerial cables. Then internal voltages and currents are computed via the surface transfer impedance of cable shields for single layer outer conductors. The penetrating field from an ESD event may induce unwanted transient voltage in the centre conductor of the cable. The calculation of the induced voltage in the centre conductor of the coaxial cable requires the details of the ESD waveform, the induced sheath current and the surface transfer impedance. The modeling of the coaxial cable is carried out to compute the sheath current, surface transfer impedance, the induced voltage and current in the centre conductor due to ESD event.