I.6.3 Array cable hook-up

Function

Hook-up and connection of the array cables to the floating substructure. This may take place directly after mooring hook-up or later if array cables are laid after the floating offshore wind turbine has been hooked up to its mooring system.

What it costs*

This is included in the floating offshore wind turbine installation contract.

Who supplies them

Boskalis, Bourbon Offshore, DOF Subsea, Global Offshore, Maersk, Société de Dragage International, Subsea 7 and Tronds Marine AS

Key facts

Array cables are either pulled directly into the floating substructure, or into a pre-installed buoyant junction box.

Pre-laid dynamic or factory jointed cables that were left to rest on the sea bed are retrieved with ROVs and transferred to the crane and winch of the support vessel. Buoyancy modules are attached at this point to form the lazy-wave shape of the dynamic section.

Platform supply vessels or multipurpose offshore vessels with a motion compensated gangway are suitable. Crews are transferred to the floating offshore wind turbine via the gangway to complete cable pull-in, termination, and connection within the turbine.

For pre-laid cables that are connected using buoyant junction boxes, the ROV and support vessel retrieves the buoyant junction box which is then pulled in and mated to the corresponding part of the junction box on the floating substructure. Electrical connection is made in the junction box.

In cases where wet or dry mate connectors are used, dynamic cable lengths may be installed at the array cable hook-up stage. This requires a support vessel with a cable carousel of sufficiently capable carrying pre-cut dynamic lengths.

  • If a dry mate connecter is used the vessel needs to retrieve the static cable or pre-installed connector from the sea bed. The crew on board the vessel then make all connections within the connector, including power and communications, before lowering the made-up connector back to the sea bed.
  • For wet mate connections it is expected that the pre-laid static cable end will have a connector pre-installed. A second connector plate is connected to the dynamic cable end and lowered to the sea bed for connection with ROV.

Two pull-ins, terminations and connections are completed at each floating offshore wind turbine where a turbine is located in the middle of a string, for the incoming and outgoing array cables.

What’s in it

Guide to a Floating Offshore Wind Farm