TenneT has hired subsea cable manufacturer Zhongtian Technology Submarine Cable (ZTT) for commissioning of five and 16 kilometres of wind farm connections.
To transport the electricity from offshore wind farms to land wind power produced off the German North Sea coast is transmitted from two wind farms to one TenneT converter platform each (HelWin beta and DolWin kappa).
There the three-phase current is transformed into direct current and transported to a ground-based converter station where the energy is converted back into three-phase current and fed into an extra-high voltage grid through a nearby transformer station.
The offshore electricity generated is collected in a transformer station platform before TenneT takes over an offshore converter station with a 155-kilovolt three-phase cable.
The cable systems will be assembled at one of ZTT’s manufacturing base in Nantong, China, and transported to Europe. The laying itself shall be carried out by the subcontractor asso.subsea (Greece). The first cable laying is scheduled for the summer of 2022 to link the Kaskasi II wind farm.
Two cable systems with a conductor cross-section of 630 square millimeters will be used to relay 342 megawatts on a five-kilometer long route between the transformer station of the wind farm and the beta of HelWin.
Using the HelWin2 grid link, the electricity is transported over 130 kilometers to the Büttel land station (Schleswig-Holstein) and fed into the extra-high voltage grid. For the cable laying that will follow in the summer of 2023, TenneT will for the first time, use an advanced three-phase cable with a conductor cross-section of 1,200 square millimeters, which will transport almost 242 megawatts from the Gode Wind 3 wind farm through a single cable system.
Various cables and pipelines to be crossed pose a particular obstacle, and the 16-kilometre-long path also passes through the Gode Wind 1 wind farm, which is already in service. Gode Wind 3 is linked to the extra-high voltage grid via DolWin Kappa and the related DolWin6 grid link in Emden/East (Lower Saxony).