Protection against common mode currents on exposed cables

Above deck cables on naval ships are exposed to High Intensity Radiated Field (HIRF) that may cause conducted interference and generate electromagnetic fields that exceed the immunity levels of commercially available equipment in the protected environment below deck. Exposed cables, such as open power plugs or lighting cables, are modelled and characterised both as a monopole antenna perpendicular to the deck and as a transmission line, representing a cable close to the deck. Below deck, these cables are connected to the power distribution network, which is from an electromagnetic interference point of view, a disordered chaotic set of unmatched transmission lines. It is shown that for exposed cable length of maximum 25 cm and not placed in the line of sight of transmitters above 400 MHz, no additional measures are needed. The effect of a simple filter is analysed.