The BorWin3 project refers to a 900MW DC grid connection system in the North Sea cluster 8 developed by TenneT Offshore GmbH. The system’s direct current is transmitted from BorWin gamma offshore converter platform to a TenneT substation located in Emden/Ost, through a 160km connection. The aforementioned length corresponds to both the onshore (30km) and the offshore (130km) cables.

The cables system that was installed is composed by:

  • 2 submarines High Voltage Direct Current (HVDC) bundled with
  • 1 submarine Fiber Optic (FO) cable

Prysmian Group has awarded Assodivers Group the installation by means of simultaneous burial (SLB) of approximately 23,000m submarine cable HVDC and FOC bundle.

More specifically ASSO‘s scope of work included:

  • Pre-lay mattress installation at crossings
  • Loading of approx. 2x 26,000m HVDC submarine cables from Pikkala, Finland and loading of approx. 26,000m FO cable in a basket at Eemshaven, Netherlands.
  • Pre – Lay Grapnel Run (PLGR) for approx. 1,100m along the cable route and visual inspection at crossing locations and wet stored cables.
  • Recovery of wet stored cable bundle and initial jointing.
  • SLB at 1.5m target DOB, approx. 22,800 in total.
  • Free lay with TDM at 5x crossings, including protection sleeves installation.
  • Wet storage at 1.0m reduced target DOB for approx. 920m.


Vessel / Equipment used

  • Atalanti
  • Artemis
  • HydroPlow
  • Atom ROV
  • AssoMat I

Project Specifications

BorWin 3 Project - SLB

Prysmian PowerLink Srl
Cable Type:
Power 2x HVDC & 1 FO bundled
Cable Weight:
Power: 40.6 kg/m FO: 3.0 k g/m in air
Cable Diameter:
Power: 128mm FO: 35mm
Service Provided:
Cable Transportation - Simultaneous Laying/Burial - Mattresses Installation
Laying Length:
Tennet Offshore GmbH
Jetting Length & Burial Depth:
Alternative Protection:
250m Mattresses
Germany, North Sea
Max Water Depth: