Protection Against Common Mode Currents on Cables Exposed to HIRF or NEMP

Abstract

Above deck, cables on naval ships are exposed to highintensity radiated fields and nuclear electromagnetic pulse (NEMP) that may cause conducted interference and generate electromagnetic fields that exceed the immunity levels of commercially available equipment above and below deck. Exposed cables, such as open power plugs or lighting cables, are modeled and characterized both as a monopole antenna perpendicular to the deck and as a transmission line, representing a cable close to the deck. The placement of an illuminated cable close to the deck is a good protection measure for long cables at low frequencies, which includes NEMP protection. The coupled pulse from a high-intensity NEMP illumination is not expected to cause damage on electric installations. 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 protection measures are needed.

Assessment of the Antenna-Equivalence Approach to Common-Mode Input Impedance Modeling

“…3(b). While the measurement setup is fundamentally different from a monopole above a groundplane, or a dipole, it is common practice to model it as such [4], [12], [14]- [16]. Due to image theory, it may also be modeled as a dipole, but if corrected for the fact that the input impedance of a monopole of length h equals half the input impedance of a dipole of length 2h [17].…”

“…Especially for higher frequencies and for cable heights above the groundplane greater than a tenth of the wavelength, the antenna behavior of a cable starts to dominate [13]. Some research has been performed on modeling a cable above a ground plane as an antenna by use of thin-wire theory [4], [12], which used the assumption that a cable acts as a monopole antenna above a ground plane [12], [14]- [16]. However, these models still use time-costly full-wave techniques, or they assumed setups that are different from reality [12].…”

Analysis of the Terminal Response Characteristics of the Twisted Three-Wire Cable Excited by a Plane Wave Field

“…Interference can be coupled with the device through the cable, interfering with the internal control signals, causing abnormalities of the device, or causing breakdown and destruction of the internal circuit chips. Therefore, it is of great significance to investigate the coupling response law of the cables to improve the electromagnetic protection ability of related devices [1][2][3].…”