HelWin 1 project is the first grid connection of offshore wind farms in the eastern North Sea. Its successful completion was a significant stage in the German grid connection project. As strong as 576 MW, this grid connection for offshore wind farms had been planned near the island of Helgoland. HelWin 1 will link two other offshore windfarms, Nordsee Ost and Meerwind, to mainland. The cable runs for 45km onshore from a newly created substation, where in Büsum the cable begins to run offshore. The distance between the coast and wind farms is around 85 kilometers.

In the HelWin 1 Grid Connection project, the consortium consisting of Prysmian PowerLink Ltd. and Siemens AG, had awarded Assodivers a contract for the installation and burial activities of the bundled DC submarine link from the 5m w.d. off the Büsum coast to HelWin Alpha offshore converter station for a distance of approx. 68km.

The HVDC and FO cables for HelWin 1 project has been manufactured in Pikkala factory in Finland in July 2012 and transported to Germany with the installation vessel CLB 'Atalanti'. At the 5m w.d. mark, three rigid joints (one per each cable) were executed so as the cables would be joined with their shallow water sections which were previously installed. Following the jointing, simultaneous laying and burial installation (SLB) was being performed using 'HydroPlow' between the 5m w.d. up to the arrival at the CAT of HelWin Alpha, at about KP85.

The operations were carried out with the target burial depth of 1.7m in the deep water section up to the 12 nautical miles line and to a target burial depth of 1.5m for the remaining portion.

Project Specifications

HelWin 1 - Grid Connections

Year:
2012
Contractor:
Prysmian PowerLink Srl & Siemens AG
Cable Type:
Power 2x250kV HVDC & 1 FO bundled
Cable Weight:
Power: 30Kg/m FO: 3.4Kg/m in air
Cable Diameter:
Power: 112mm FO: 37mm
Service Provided:
Cable Transportation - Simultaneous Laying/Burial
Laying Length:
67,426m
Owner:
TenneT
Jetting Length & Cover Depth:
20,292m @ 1.5m / 443m @ 1.55m / 46,691m @ 1.7m
Location:
North Sea, Germany
Max Water Depth:
26m