Erlangen, Germany, August 2, 2011 — Working in consortium with the Italian cable manufacturer Prysmian, Siemens Energy is erecting HelWin 2, the link between the North Sea offshore wind farm Amrumbank West and the onshore grid.
The customer is TenneT TSO GmbH of Bayreuth, Germany. The order brings more than half a billion euros onto the consortium's books. The grid connection, designed as a high-voltage direct-current transmission link, has a rating of 690 MW and is scheduled to be operational by 2015.
Amrumbank West will have a power capacity between 300 and 400 MW. Together with the Meerwind and North Sea East offshore wind farms, Amrumbank West is part of the North Sea cluster HelWin.
The centerpiece of the HelWin 2 link-up is the offshore converter platform HelWin beta, on which the Siemens HVDC Plus system for high-voltage direct-current transmission is installed. It also houses two power transformers and the gas-insulated high-voltage switchgear.
Siemens is responsible for turnkey supply of the fully equipped floating and self-erecting platform, also known as a wind power offshore substation, or WIPOS for short. TenneT has also awarded Siemens a contract to carry out all maintenance work on the platform and on the on shore transformer substation for an initial period of five years.
This includes coordination and logistics efforts as well as performance of all necessary inspections, preventive and corrective maintenance, spare parts management, and drawing up the maintenance schedules.
The 3-phase alternating current generated by the wind turbines will be bundled on the offshore transformer platform and transmitted to the converter platform via high-voltage cable. There the alternating current arriving at a voltage of 155 kV will be stepped up and converted into direct current in the Siemens HVDC system.
The electric power will then be transmitted at a voltage of ±320 kV via a submarine high-voltage cable from the feed-in point on the platform to the grid connection point in Büttel, northwest of the city of Hamburg, over 130 kilometers away. There, a transformer and converter substation will convert the power back into alternating current for onward transmission and distribution.
Another special feature of the HelWin beta offshore converter platform is that it will be connected via a bridge to its parent platform HelWin alpha to allow shared use of the helicopter deck and crew quarters.
There will also be an AC cable link to the busbar of the platform's 155 kV switchgear and a link to the emergency power system. The HelWin alpha platform, via which the North Sea East windfarm is connected to the grid, forms an integral part of the Helwin1 link-up.