It is the fourth high voltage direct current grid link completed by Siemens on behalf of TenneT.
The earlier three, the 800MW BorWin 2, 576MW HelWin 1 and 864MW Sylwin 1 links, were delivered in January, February and April this year respectively.
Siemens carried out the projects in a consortium with Italian cable specialist Prysmian.
The offshore platform of the HelWin2 link is situated around 85km off the northwest coast of the island of Helgoland.
HelWin 2, which is now online, can transmit enough energy for about 900,000 households.
With a transmission capacity of more than 2.9GW installed in the North Sea, the four grid connections can deliver enough energy for about four million households in Germany.
TenneT member of the managing board Lex Hartman said: "The completion of HelWin2 marks an important milestone for us. Step by step we are implementing the offshore development goals set by the German government.
"The goal of the German government is to have 6.5 gigawatts of offshore wind power capacity installed by 2020. TenneT has already achieved more than 50 percent of this target."
TenneT has contracted Siemens and Petrofac for a fifth link, the 900MW BorWin 3, which is expected to be operational in 2019.
Image: The offshore platform of the HelWin2 link is located about 85km off the northwest coast of the island of Helgoland. Photo: courtesy of Siemens AG.
