The SylWin 1 project, located 70km west from the island of Sylt, involves a 864MW DC link which will be able to feed large quantities of wind power into the German grid. The link is able to supply up to 1.5 million German households with wind-generated power. 

The wind farm is connected to the mainland grid via a high-voltage direct-current (HVDC) transmission link using subsea and underground cable and Prysmian PowerLink Srl had been awarded the procurement of the submarine cables for this transmission. The network connection is to be operational as of early 2014.

The installed HVDC marine cable connection from the windpark to the landing point on mainland has a length of approximately 160km and from the landing point to the converter station in Büttel has an overland cable length of approximately 45km.

Prysmian awarded Assodivers with a subcontract for the submarine cable laying and protection of the SylWin1 cable in the North Sea. The scope of work included utilization of the CLB 'Atalanti' for the loading of 2x52km HVDC cable from Pikkala, Finland and 1x52km FOC placed in a basket from Bremerhaven, Germany and simultaneous laying and burial of the bundled cables from approximately KP107 to KP55, using 'HydroPlow' underwater burial vehicle.

On completion of this operation, the vessel was again transited to Pikkala in order to load 2x38.3km HVDC cables and then 1x38.3km FOC from Bremerhaven that were simultaneously laid and buried in bundle from approximately KP55 to KP17. In addition, the SoW also included assistance to initial cable jointing operation with the previous laid cables and final cable jointing operation with the shallow water cable.

Project Specifications

SylWin 1

Prysmian PowerLink Srl
Cable Type:
Power 2x250kV HVDC & 1 FO bundled
Cable Weight:
Power: 38.8Kg/m FO: 3.4Kg/m in air
Cable Diameter:
Power: 126mm FO: 37mm
Service Provided:
Cable Transportation - Simultaneous Laying/Burial
Laying Length:
Jetting Length & Burial Depth:
51,906m @ 1.7m / 38,023m @ 1.5m
North Sea, Germany
Max Water Depth: