Nordergründe, Germany

• Cable system design and manufacturing of 3x4 km of single-core HVAC underground XLPE cable and 26.5 km of 3-core HVAC submarine XLPE cable with integrated fiber optics.
• Offshore and onshore shunt reactors.
• Substation extension.
• Installation and commissioning.

The Nordergründe wind farm, located in the North Sea off the coast of Germany, is part of Energiewende, the German government´s strategy to increase the share of renewable energy in the national energy mix. At the substation Inhausen, north of Wilhelmshaven, the power generated by the 18 offshore wind turbines is fed into the 220 kV (kilovolt) grid.

The wind farm has a capacity of 111 MW (megawatt), which is enough to cover the electricity needs of more than 100,000 households on the mainland. The energy generated by the wind farm enables the replacement of fossil fueled power generation and reduces CO2 emissions by up to 500,000 tons per year.

The substation of the wind farm is situated less than 28 kilometers from the coast. Considering this as well as the installed capacity, the Dutch-German transmission grid operator TenneT, responsible for connecting offshore wind farms in the North Sea to the high voltage grid onshore, realized that the most efficient method to connect the wind farm, from both technical and financial perspectives, was an AC (alternating current) grid connection. This also called for an extension of the substation.

Being world-leading high-voltage cable manufacturer, we have extensive knowledge and experience across a range of applications including offshore wind farm connections and we already had received large orders from TenneT. We were selected for the mission in 2012.

The project scope included the design, engineering, supply and installation of the 155 kV underground and submarine XLPE AC cable system, the onshore and offshore shunt reactors and the extension of the existing 220 kV substation.

The horizontal drillings below the dike at the landing point near Hooksiel, the laying of the four kilometers of underground cable and the works at the substation in Inhausen were completed without problems. Then the project was delayed because the manufacturer of the offshore wind farm substation filed for insolvency.

The works in substation Inhausen and the installation of the underground cable was nalized and handed over to TenneT in April 2014. In 2015, our work with the submarine cable and offshore shunt reactor could restart. The coastal line is an environmental protected area and there is one pipe-crossings in the sea along the cable rouute. Thanks to the vast experience in special requirements, we were able to handle the cable laying and installation according to all regulations and in close cooperation with the local authorities and the suppliers.

After the completion of the platform in September 2017, we made the nal connection of the submarine cable system– and successfully commissioned the NKT project on time. Our experience and highskilled expertise in turnkey solutions has yet again resulted in a greatly accomplished project. When we have the total responsibility and work close with our customer and suppliers, we can ensure maximum efficiency and lower risks in project interfaces.