TenneT's giant offshore 'power socket' reaches final destination in the North Sea
Wednesday, Aug 28, 2013
TenneT’s largest converter platform, DolWin alpha, has been installed in the North Sea. Here the topsides of the platform was lifted by the world's largest crane vessel, Thialf, and positioned on top of the already installed jacket. The converter platform is one of the main components of the TenneT DC (direct current) offshore grid connection DolWin1. The topsides of the platform is 62 metres long, 42 metres wide, 42 metres high and has a lifting weight of 9,300 metric tonnes.
“The installation is a significant moment for TenneT”, says Lex Hartman, member of TenneT’s managing board. “DolWin1, the largest grid connection in the German North Sea, has moved a major step towards completion: In 2014, DolWin1 will be able to transport 800 MW of clean green energy to the German grid.”
A few days before the installation, the sailout of the topsides started. A barge transported it from the quayside in Schiedam where it was moored for final completion to its destination 75 kilometres off the East Frisian coast. When the jacket, the steel substructure which was completed last autumn, had been prepared for the upcoming installation, the most challenging installation phase started: Thialf lifted the topsides, weighing 9,300 metric tons, and lowered it very carefully onto the jacket. Next, the jacket and topsides are welded together, after which the hook-up and commission work can start. Now the final works for completing DolWin alpha are carried out including connecting the high voltage subsea cable to the platform and offshore pre-commissioning tests. ?
The platform is a crucial part of the entire offshore grid connection called DolWin1. DolWin alpha will convert the alternating current (AC) from the wind farms into direct current (DC). The direct current will then be transported via 75 kilometres of high voltage direct current (HVDC) sea cables and 90 kilome-tres of HVDC land cables to the converter station onshore in Dörpen-West where it will be converted into alternating current again so that it can be fed into the grid. This offshore direct current grid connection system will have a length of 165 kilometres and a capacity of 800 MW.
The platform of DolWin1 was built by Heerema Fabrication Group’s Zwijndrecht yard, as a subcontrac-tor of TenneT's main contractor ABB, who was responsible for the construction of the platform and in-stallation of the complete electro technical equipment using HVDC Light converters as basic technology.