The offshore platform of the SylWin1 grid connection is located 70 kilometres west of the island of Sylt. It is the third offshore connection this year and enables electricity generated from offshore wind power to be transmitted via a subsea and underground cable link to a land-based station at Büttel. The cable is more than 200 kilometres long and supplies up to 864 MW of green electricity, enough to power more than a million German households.
“This year we have completed the world's first three offshore grid connections with efficient direct-current technology - SylWin1, BorWin2 and HelWin1” said Jan Mrosik, CEO of the Siemens Energy Management Division. “We also intend to put the fourth project HelWin2 into commercial operation as planned in the coming weeks.”
Lex Hartman, member of the managing board of TenneT TSO GmbH, added that 2015 is a special milestone year for the company, which will be completing further offshore grid connections by the end of year resulting in an overall capacity of more than 5,000 MW. This represents more than two-thirds of the offshore expansion goal set by the Federal German government, which is aiming to install 6,500 MW by 2020.
Three offshore wind farms - DanTysk, Butendiek and Sandbank – are linked to SylWin1. Each has a capacity of 288 MW. DanTysk and Butendiek incorporate 80 Siemens 3.6 MW wind turbines while Sandbank will have 72 turbines rated at 4 MW. Currently, more than 100 wind turbines are already linked to the grid connection, with new turbines being connected on a daily basis. Under optimal conditions, 350 MW can be transmitted via the SylWin1 grid link.
A fourth grid connection, HelWin2, is scheduled to take up commercial operation in the first half of 2015 while a fifth, BorWin3, will be delivered in 2019. The grid connections implemented by Siemens for TenneT will have a total transmission capacity of more than 3.8 GW, providing electricity from offshore wind power to supply nearly five million households.
The Siemens HVDC technology reduces transmission losses for each grid connection to less than four percent. The technology is installed on the offshore platforms and in the land-based converter stations and is equipped with HVDC Plus self-stabilisation to enhance grid stability and reliability.
Transmission system operator TenneT contracted the consortium comprising Siemens and the Italian cable specialist Prysmian for the HelWin1 offshore grid connection early in 2011. The offshore platform was built by Nordic Yards in Germany. In total, Siemens has been awarded five North Sea grid connection projects by TenneT: HelWin1 (576 MW) and HelWin2 (690 MW) off of Helgoland, BorWin2 (800 MW) and BorWin3 (900 MW) off of Borkum and SylWin1 (864 MW) off of Sylt. Three of these, BorWin2, HelWin1 and SylWin1, have already taken up normal operation.
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