Progress updates – Wet design cables

Traditionally, cable systems of wet design have been rated 36 kV or lower. High-voltage subsea cables can have a “dry design” or “wet design”. A “dry design” means there is a metallic water barrier (typically, an extruded lead sheath) outside the cable core, which will keep the insulation system dry for the lifetime of the cable. A cable with a “wet design” does not have a metallic water barrier, which means water will permeate through the polymer sheaths and saturate the insulation system with water over time. In this project, Nexans together with SINTEF, Equinor and Statnett are developing a 66-kV wet design cable with an aluminium alloy conductor.

The recent push to develop cables with a wet design is driven by environmental, market and technical factors. Wet design cables contribute to a smaller environmental footprint primarily by being lead-free and significantly lighter than traditional dry cables. Commercially, wet design cables are cheaper and can be used in dynamic applications, such as floating energy production.

Ocean Grid SP2 combines a wet design cable with an aluminium alloy conductor to develop one of the lightest and strongest wet design HV cable cores on the market today.

The main activities in this sub project include the study of corrosion biproducts and their effect on degradation of the insulation system, as well as cable manufacturing, testing and ageing.