"The interconnection comprises of HVDC subsea and land cable types at a voltage of ± 320 kV DC to be supplied by Prysmian along a 159 km sea route ... and continuing along a 45 km land route to the land converter station in Büttel" and "employing an extruded cable connection along a total route of approximately 205 km (160 km offshore and 45 km onshore)."
Prysmian Group was awarded a contract by Dutch-German transmission system operator TenneT as part of the Siemens–Prysmian consortium to deliver the cable system for the SylWin1 HVDC offshore grid connection. The scope covered design support, manufacture, supply, installation and commissioning of the ±320 kV HVDC extruded subsea and land cable system along a 160 km offshore and 45 km onshore route between the SylWin alpha offshore converter platform and the onshore converter station at Büttel. Prysmian also supplied and installed 155 kV HVAC submarine cables linking the offshore wind farm transformer platforms (including DanTysk, Butendiek and later Sandbank) to the SylWin alpha converter platform, as well as associated fibre-optic cables and accessories. Manufacturing took place from 2012, with offshore and onshore installation activities in 2012–2013, and the system was successfully commissioned and handed over in 2015.