All 48 wind turbines are connected with each other by so-called inter-array cables and linked to a substation. Altogether, this requires more than 60 kilometres of cables. The 33-kilovolt underwater cables of ABB have a diameter of up to 16 centimetres. A particularly robust sheath protects them from the extreme stresses caused in particular by the installation process out at sea. At the same time, they guarantee maximum power transmission across large distances. These high-performance power lines are installed by special-purpose cable-laying vessels.
Transformation for onshore transmission
The offshore substation is the nerve centre of the wind farm. It transforms the electricity generated by the wind power systems at 33 kilovolt (kV) to a transmission voltage of 155 kV. High-voltage submarine cables transmit the electricity from here to the coast. Such an offshore substation is about 18 metres high and weighs approx. 2,100 tons. Like the wind turbines, it is mounted on top of a steel structure foundation in the sea bed and juts out approx. 37 metres above the sea level after final assembly. The electricity generated by the individual wind power systems is pooled in the offshore substation before it is transmitted to the nearest grid connection point at Brunsbüttel through high-voltage subsea cables. The grid operator Tennet is responsible for the network connection.