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TenneT presents Hub and Spoke concept for large scale wind energy on the North Sea.

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TenneT is a leading European electricity transmission system operator (TSO), with activities in the Netherlands and in Germany. We strive to ensure a reliable and uninterrupted supply of electricity in our high-voltage grid for some 41 million people.

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First DC power link between an offshore wind park and the high voltage grid



  • 200 km long and 400 MW capacity
  • 75 km onshore cable
  • 125 km offshore cable

Grid connection point

  • converterstation Diele Germany

Status of project

  • online since april 2010

About the project


The first project realized using DC technology is the grid connection for the wind park BARD Offshore 1. The project name BorWin1 is based on the wind park cluster of Borkum Island. TenneT installed an offshore converter station for transporting wind energy from sea to land. There, the electricity produced by the wind park farm is converted into direct current (DC) power and transported via a High Voltage Direct Current cable line through the North Sea and overland via cable to the nearest grid connection point onshore – a landward converter station in Diele. In the converter station the DC power is converted into three-phase current and afterward fed into the grid.

DC is primarily preferred when transporting high energy via long distances. This condition exists especially in case of connecting big offshore wind farms.

The land route from Hilgenriedersiel to Diele is about 75 kilometers long. In May 2008, there was the start of the construction of the land cable connection from Hilgenriedersiel to the substation in Diele. In summer 2008, eight underground horizontal drillings occurred underneath the dunes and dikes of Norderney Island and near Hilgenriedersiel for the conduit structure of the first DC cable. For the protection of the National Park Wadden Sea the DC cable was pulled into the conduit system and the sea cable was connected to the land cable. In 2009 the remaining laying process of the total of 200 kilometers of cable offshore took place – to the substation Diele near Papenburg via Norderney. 


Already at the beginning of June 2009 TenneT had installed the offshore converter platform BorWin alpha. The connection to the substation platform of the wind park BARD Offshore 1 followed.

After TenneT had also completed the technical installation at the substation in Diele, the test and trail operation was started. In the local converter station the DC power is converted into three-phase current and fed into the 380-kV-grid. The 200 kilometer long total distance was until then the world's longest link constructed for connecting an offshore wind park. The company ABB was contracted to construct the HVDC link with a capacity of 400 MW. With the completion of the first wind power station of the wind park BARD Offshore 1 BorWin1 is feeding energy into the German transmission system since the beginning of December 2010. 


Cornelia Junge

Pressereferentin - Projektkommunikation Offshore

0049 (0)5132 89-2357

BorWin1 project

In commission since April 2010.

Project downloads

Factsheet BorWin1 (german) (248 KB, pdf, 05/15/2016)

Erste deutsche Gleichstromverbindung zu einem Windpark auf See.

Category: Brochures
Factsheet BorWin1 (german) Download Download
Die Naturschutzprojekte von TenneT (german) (785 KB, pdf, 08/02/2016)

Aufwertung der Lebensräume von zahlreichen Pflanzen- und Tierarten

Category: Brochures
Die Naturschutzprojekte von TenneT (german) Download Download

Also interesting

TenneT Offshore factsheet

"Energie von See an Land" factsheet about TenneT offshore projects (german only)

Offshore projects in Germany

Our other german offshore projects.

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Media footage BorWin1

Your way to our pressfootage.

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