RWE Innogy: Wedding on the high seas

A wedding was celebrated on the Nordsee Ost offshore wind farm construction site of RWE Innogy: This is what the construction process is called when the foundation is successfully married to the substation platform. As a result the sea-based transformer substation and all its electrical components have now been successfully completed.

The journey of the 1,800 ton substation started in Danish Aalborg and took three days to ship across the North Sea. The substation is 15 meters above the construction area of RWE Innogy’s Nordsee Ost offshore wind farm, which is located some 30 kilometres north of the island of Heligoland. A floating crane placed the heavyweight substation onto the foundation on Saturday, completing the installation of the heaviest component of the offshore wind farm.

“The substation was developed and built within a 16 month time frame by our contractor Bladt Industries, a steel construction company, together with the Danish subcontractors Semco and ISC,” said Matthias Esken, Project Manager for the transformer substation at Nordsee Ost. “We are now going to connect the substation with the previously installed inner-array cables and the TenneT export cables which remain to be installed.” And Marcel Sunier, Project Director for the Nordsee Ost wind farm at RWE Innogy, added: “The heart of the wind farm has now been installed with the transformer substation. As soon as access to the grid has been provided, we will start the commissioning. The wind farm is expected to be complete at the end of 2014, with the testing phase to be finished in spring 2015.”

The offshore substation transforms the electricity generated by the 48 wind turbines at 33 kV (kilo volt) to a transmission voltage of 155 kV. Submarine high-voltage cables then transmit the electricity to the transformer platform of TenneT where the AC voltage is transformed to 250 kV DC voltage and transmitted to the nearest grid access point at Brunsbüttel. The grid operator TenneT is responsible for the grid access.

Like the wind turbines, the transformer substation was anchored on a jacket foundation to the seabed and will rise about 40 meters above the sea level following final assembly.

Once complete, the Nordsee Ost offshore wind farm will have an installed capacity of some 295 megawatts and supply the equivalent of about 300,000 private households with electricity per year. Equipped with the currently most powerful offshore turbines, Nordsee Ost ranks among the largest commercial wind power projects off the German coast.