HelWin alpha and HelWin beta offshore converter platforms

TenneT Chooses ZTT for Two German Offshore Wind Connections

TenneT has commissioned subsea cable manufacturer Zhongtian Technology Submarine Cable (ZTT) for two offshore wind connections in Germany.

TenneT (archive)

ZTT will deliver cable systems to link offshore wind farms to HelWin beta and DolWin kappa converter platforms in the North Sea, with the cable routes being five and 16 kilometre respectively.

The cable systems will be produced at ZTT’s manufacturing base in Nantong, China, and then transported to Europe, with the cable-laying operations to be carried out by the subcontractor asso.subsea from Greece.

The first cable laying is planned for summer 2022 to connect the Kaskasi II project and the second one is expected to take place the following year for the Gode Wind 3 offshore wind farm.

For the Kaskasi II offshore wind farm, two cable systems with a conductor cross-section of 630 square millimeters will be used to transmit 342 MW via the five-kilometer long route between the wind farm’s transformer station and HelWin beta. Through the HelWin2 grid connection, the electricity is transported over 130 kilometers to the land station in Büttel in Schleswig-Holstein and fed into the extra-high voltage grid.

For the the Gode Wind 3 connection, where work will be carried out in the summer of 2023, TenneT uses a three-phase cable with a conductor cross-section of 1,200 square millimeters the first time. The cable will transport the almost 242 MW from the wind farm via just one cable system. The route, which is over 16 kilometers long, also runs through the Gode Wind 1 wind farm, which is already in operation. Gode Wind 3 is connected to the extra-high voltage grid via DolWin kappa and the associated DolWin6 grid connection in Emden.

TenneT issued a call for tenders seeking turnkey construction solutions to connect the 342 MW Kaskasi II and the 242 MW Gode Wind 3 wind farms in February of this year.

The 130-kilometer HelWin2 HVDC transmission connection has been operational since 2015, and can accommodate a maximum capacity of 690 MW. The connection comprises 45 kilometres of land cable and 85 kilometres of subsea cable.

The DolWin6 HVDC offshore grid connection, which is scheduled to be on line in 2023, is 90 kilometres long with a maximum connection capacity of 900 MW. It will be linked to the grid by 45 kilometres of land cable and 45 kilometres of subsea cable.