Numerical Analysis of Cable SGEMP Responses in Multiwire Bundles

When an equipment like a laboratory-measurement system is exposed to X-ray irradiation, cables, cavities, and printed-circuit boards in the equipment could generate system-generated electromagnetic pulse (SGEMP). Cable SGEMP is one of the important SGEMP effects, and a multiwire bundle may suffer a more complex cable SGEMP response than a coaxial cable, and it is more difficult to analyze the damage effect. In this study, a general cable SGEMP model is established based on the field-line coupling model of the multiconductor transmission line and the electric field coupling model, and quasi-electrostatic field model of the photon-driven current source. The cable SGEMP effect of a seven-wire unshielded cable bundle is studied. The results showed that the cable SGEMP current is mainly affected by the potential of wires and the crosstalk between wires and that between the wires and the reference ground. The potential depends on the position of wires relative to the reference ground and the spatial distribution of charge density in the coupling system, whereas the crosstalk is mainly related to geometric structure and materials. When the cable bundle is far away from the reference ground, the load current of each wire will generally decrease because of the decrease in direct Earth capacitance. The change of the X-ray irradiation direction could change the load current, and the load current of wires irradiated earlier shows an increasing trend. The increase in the load resistance of a wire may cause an increase in the load current of other wires through inductive coupling, which provides a technique for reducing the current of specific wires in a cable bundle.