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Since 2016, three wind farms have been connected to the transmission grid via the 135-kilometre long DolWin2 grid connection.

Lower Saxony, North Sea
  • DolWin2

About the project

135 kilometre long and 916 megawatt strong direct current connection


In addition to 45 kilometres of submarine cable, TenneT also laid 90 kilometres of land cable, which run from the coast to the onshore converter station Dörpen/West in Emsland. There, the direct current is converted back into three-phase alternating current, fed into the transmission grid by the transformer station and redistributed to consumption-intensive regions. With a transmission capacity of 916 megawatts (MW), DolWin2 can supply more than one million households with clean wind energy per year.

For DolWin beta, the heart of the DolWin2 grid connection, TenneT opted for an innovative installation concept: the platform was anchored to the seabed by gravity alone. This design simplified the installation of the offshore converter platform, as it meant that no piles had to be driven into the seabed and no crane ship was required. To stabilise the platform, water was slowly pumped into the six steel legs during installation, causing it to sink to the seabed. Subsequently, the water in the steel legs was replaced by gravel and sand to fix the platform permanently. DolWin beta thus defies the harsh North Sea conditions and is always calm in the water even in strong waves.


Connecting concept

The electricity generated at sea is collected in the wind farm's own transformer station. From there the energy is transported to TenneT’s offshore converter platform via a 155 kilovolts three-phase alternating current (AC) cables. The conversion of AC to direct current (DC) takes place in the offshore converter station. The electricity is then transported by submarine and underground cable to the corresponding land station. Here, the electricity is converted back into AC and fed into the TenneT extra-high voltage grid.


  • DolWin2 HDD Hilgenriedersiel

    In fragile ecosystems, TenneT uses horizontal directional drillings as they enable trenchless cable laying.

  • DolWin2 HDD Norderney

    By using horizontal directional drillings, the cables were laid on the island of Norderney.

  • DolWin2 HDD Norderney

    The cables are laid out on conveyors in the beach area.

  • DolWin2 convertion Dörpen West construction site

    The onshore converter station of DolWin2 is located in Dörpen/West.

  • DolWin2 HDD Hilgenriedersiel

    Dikes, dunes and tidal flats are drilled under. The plastic pipes are pulled into the boreholes, and later the cables are pulled in.

  • DolWin beta Sailout

    The DolWin beta offshore platform built in Dubai is on its way to its destination in the North Sea.

  • DolWin_beta

    The complete platform weighs around 23,000 tons and is around 100 metres long, 70 metres wide and 100 metres high.

  • Nordsee_One-1

    In total, three wind farms are connected to the German electricity grid via DolWin2.


cornelia junge.jpg

Cornelia Junge

Spokesperson - Project Communication Offshore

Further information