Function
The cable is buried to a predefined depth under the sea bed to ensure protection from external aggression (for example fishing and anchoring) as well as to prevent exposure due to sea bed mobility.
What it costs*
Cable burial for a 1 GW wind farm costs around £44 million.
Who supplies them
The burial and burial tools are usually provided by the cable installation contractor.
Vessel contractors: Assodivers, Boskalis, Canyon Offshore (Helix ES), Global Marine, Jan de Nul and Van Oord Offshore Wind.
Manufacturers include Canyon Offshore (Helix ES), Osbit, Royal IHC and SMD.
Key facts
Burial can be achieved either at the same time as the lay of the cable (simultaneous lay and burial) or afterwards (post-lay burial). If the former method is used, a Cable plough [I5.4.2] is used simultaneously during the cable lay to create a trench in which the cable falls and is immediately buried. In the case of a post-lay burial, the vessel will move along the laid cable, using a or Vertical injector and jetting sled [I5.4.4] to fluidise the sediment and allowing the cable to be buried.
Burial depths are determined based on an industry standard (burial protection index and/or cable burial risk assessment). Generally, cables are buried at a depth of 1-4 m below the sea bed.