Siemens was contracted by TenneT in 2010 as part of a consortium for the HelWin1 offshore grid connection. Siemens supplied the HVDC conversion technology for the HelWin Alpha offshore converter platform and supplied the land-based converter station at Büttel. Siemens executed key offshore works including installation of the HelWin1 platform and prior installation of the platform support substructure at the offshore site. Siemens was also contracted by TenneT to provide maintenance of the HelWin1 grid connection for an initial period of five years.