Understanding the exposure of marine life to electromagnetic fields generated by subsea cables

Abstract

Electromagnetic fields (EMF) generated by wave and tidal energy subsea power cables can potentially impact marine life. Recently reported effects include: a) cable avoidance/attraction, b) behaviour changes, such as foraging and swimming, c) change of migration routes and d) alterations in early stage development. The source of the EMF, the subsea cables, are buried in the sediment or placed on top of the seabed (if hard substrate) for fixed devices and for floating devices the cables will also be deployed in the water column. Most determination of the extent of EMF comes from modelling, which estimates cable EMF to extend a few metres into the surrounding environment and drop off rapidly with distance from the cable axis. However, recent studies of operational offshore wind devices have measured the actual EMF in the environment up to 10s of metres from a cable, which increases the likelihood of encounter by marine life. Therefore, this study describes a new measurement methodology to better understand how the cable EMF propagates into the surrounding environment. We show initial results using the new method of data collection to compare and contrast EMF modelling and measured data. The new methodology consists of two fluxgates: one is stationary on the cable while the other moves perpendicular to the cable. Measured EMF emitted by HVAC power cables as a function of distance will be presented. We will then present the context of how this understanding of the EMF environment may assist in understanding how marine fauna may be impacted. EMF from power cables is comparable between renewable technologies for similar electrical currents transmitted if the cable properties are the same.