Giant offshore 'socket' HelWin beta starts journey

16 June 2014, Zwijndrecht

On Saturday June 14, the HelWin bèta topside left Heerema Fabrication Group’s (HFG’s) yard in Zwijndrecht. TenneT's giant converter station was transported along the river the Oude Maas to Schiedam for the last fabrication activities. This operation marks the start of a journey on which the platform will sail to the Helgoland area in the German North Sea. Here it will be positioned on top of the already installed jacket in August 2014.

TenneT's 690 MW transmission link will connect offshore wind farm Amrumbank West located in the cluster HelWin in the eastern North Sea to the German grid. The wind farms from Amrumbank West will be connected with AC cables to the HVDC converter platform situated in the North Sea and further through 85 km of DC sea cable and 45 km of land cable to the HVDC onshore station at the grid connection point at Büttel. The connection is due to be operational in 2015.

HFG started the construction of the 10,200-tonne HVDC topside in October 2012, after winning the contract from Siemens in June that year for the Engineering, Procurement, Construction and Installation (EPCI) of the HelWin beta platform. The 4,500-tonne jacket for the project was constructed at HFG’s yard in Vlissingen, and installed by HMC’s crane vessel Thialf in April 2014. The HelWin bèta topside measures 98 meters in length, 42 meters in width, and 28 meters in height.

HFG’s CEO Koos-Jan van Brouwershaven says, “This EPCI project stands out because of its complexity and size. We managed and built both the jacket and topside in a relatively short period of 20 months, a significant performance and quite unique for wind energy projects. The project’s complexity is due to the fact that a closed structure will be installed offshore which will have a controlled and acclimatized environment on the inside.”

Supplying power to 700,000 German homes
The platform is equipped with Siemens’ High Voltage Direct Current (HVDC) technology allowing a low-loss transmission of wind power generated in the German sector of the North Sea. The converter platform is one of the main components of the TenneT DC offshore grid connection HelWin2. The offshore converter station’s 690MW transmission capacity will supply power to about 700,000 homes in Germany.

Energie wende
As an international high voltage grid operator TenneT delivers an essential contribution to the 'Energiewende' in Germany by bringing offshore wind energy to land and by strengthening its onshore net. Currently, TenneT is working on ten projects to connect wind farms in the German North Sea. These projects total 8,000 megawatt of renewable electricity, enough energy to supply over 8 million households.  With these projects TenneT delivers a huge contribution to the transition to a sustainable energy supply.