Abstract
The characteristics of the electromagnetic (EM) field emissions from a subsea cable, based on subsurface field measurements and modeling, are described. The work is in support of characterizing the EM field emissions associated with subsea power transmission cables that will link marine hydrokinetic devices to shore, and assessment of their environmental impact on aquatic species. Previous studies suggest that several species can detect variability in the electric and magnetic fields in the water column and utilize them for navigation, searching for food and other life activities (see e.g. [1]). There is therefore some concern that anthropogenic sources of variability in the EM field may have negative impact on these species. The nature of EM field emissions from subsea cables depend on the transmitted power, whether the power supply is AC or DC, the frequency and amplitude of the AC current, cable construction, and whether the cable is monopole, bi-pole or tri-axial [2]. EM field emission levels from a power carrying cable decays inversely with distance from it. The electric field depends on the potential across the cable and increases with it while the magnetic field depends on the flow of current through the cable and increases with the magnitude of the current. A COWRIE report [3] concludes that, despite a number of modeling studies and laboratory and field experiments (see [4] for a review), the current state of knowledge regarding the EM field emitted by submerged power cables is variable and inconclusive and more field data on EM field emissions from subsea cables are needed in order to develop suitable predictive models. The overall aim of the present study was to develop a system for characterizing electric and magnetic field emissions from anthropogenic sources through field observations and physics-based modeling, in support of providing accurate predictive models of the emitted fields that are verified thro ugh comparison with field measurements.