HVDC HelWin1 is a

high voltage direct current A high-voltage direct current (HVDC) electric power transmission system (also called a power superhighway or an electrical superhighway) uses direct current (DC) for electric power transmission, in contrast with the more common alternating curren ...

(HVDC) link built to transmit Offshore wind power to the

power grid An electrical grid is an interconnected network for electricity delivery from producers to consumers. Electrical grids vary in size and can cover whole countries or continents. It consists of:Kaplan, S. M. (2009). Smart Grid. Electrical Power ...

of the German mainland. The project differs from most HVDC systems in that one of the two converter stations is built on a platform in the sea. Voltage-Sourced Converters are used and the total cable length is 130 km. The project was completed and handed over to its owner, TenneT, in February 2015.

Context

HelWin1 is part of an ambitious programme of providing grid connections to offshore wind parks off the coast of Germany, in the German Bight, as part of the German

Energiewende The ''Energiewende'' (; ) is the ongoing transition by Germany to a low carbon, environmentally sound, reliable, and affordable energy supply. The new system intends to rely heavily on renewable energy (particularly wind, photovoltaics, and ...

(Energy Transition) programme. HelWin1 forms part of the ''HelWin cluster'', named after the German island of

Heligoland Heligoland (; german: Helgoland, ; Heligolandic Frisian: , , Mooring Frisian: , da, Helgoland) is a small archipelago in the North Sea. A part of the German state of Schleswig-Holstein since 1890, the islands were historically possessions ...

. HelWin1 has been built to transport power from the Nordsee Ost and Meerwind Süd/Ost wind parks.

HVDC A high-voltage direct current (HVDC) electric power transmission system (also called a power superhighway or an electrical superhighway) uses direct current (DC) for electric power transmission, in contrast with the more common alternating curren ...

has been chosen for most of the grid connections because the relatively long distance involved – both from the wind park to shore and from the shore to the nearest suitable connection point to the onshore grid - makes conventional alternating current transmission uneconomic.

Technical aspects

HelWin1 uses Voltage Sourced Converters (VSC) to convert from AC to DC and back again, using 4.5 kV IGBTs as the switching elements. One converter is provided at each end of the link with a DC voltage of ±250 kV and a transmission capacity of 576 MW. The converters, built by

Siemens Siemens AG ( ) is a German multinational conglomerate corporation and the largest industrial manufacturing company in Europe headquartered in Munich with branch offices abroad. The principal divisions of the corporation are ''Industry'', '' ...

, use the Modular Multi-Level Converter technology, in the symmetrical monopole configuration. Each converter station is equipped with two, three-phase transformers in parallel, each rated at 425 MVA (offshore) and 422 MVA (onshore). Each converter valve is equipped with a dry-type valve reactor of 50 mH. The offshore converter is located on the HelWin Alpha platform, which was built by

Nordic Yards Nordic most commonly refers to: * Nordic countries, written in plural as Nordics, the northwestern European countries, including Scandinavia, Fennoscandia and the North Atlantic * Scandinavia, a cultural, historical and ethno-linguistic region in ...

Warnemünde (, literally ''Mouth of the Warnow'') is a seaside resort and a district of the city of Rostock in Mecklenburg, Germany. It is located on the Baltic Sea and, as the name implies, at the estuary of the river Warnow. is one of the world's busie ...

. The ''topside'' of the platform is of the ''float-over'' type which is designed to be floated out to the installation site and then jacked up onto the submerged supporting structure using the support legs that are integral to the structure. The topside has a total weight of 12000 tonnes and measures 75 m x 50 m x 23 m high. Each of the two 250 kV cables linking HelWin Alpha to the onshore substation has a total length of 130 km, of which 85 km is sea cable and 45 km is underground land cable. The sea cables come ashore close to Büsum and continue, as land cables, to the onshore

converter station An HVDC converter station (or simply converter station) is a specialised type of substation which forms the terminal equipment for a high-voltage direct current (HVDC) transmission line.Arrillaga, Jos; High Voltage Direct Current Transmission, se ...

Büttel Büttel is a municipality in the district of Steinburg, in Schleswig-Holstein, Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Rus ...

. The cables were supplied by

Prysmian Prysmian S.p.A. is an Italian company with headquarters in Milan, specialising in the production of electrical cable for use in the energy and telecom sectors and for optical fibres. Prysmian is present in North America with 23 plants, 48 in Eur ...

and use extruded Cross-linked polyethylene insulation.

Construction schedule

The HelWin1 project was ordered in 2010. The platform was installed on 26 August 2013. Commissioning was completed in January 2015 and the project was handed over to TenneT in February 2015 although at the time of hand-over, only 288 MW of wind power was connected to the converter station Siemens hands over HelWin1, the second North Sea grid connection to TenneT
Webwire.com.

Connected wind farms

* Meerwind Süd Ost (288 MW) * Nordsee-Ost (295.2 MW)

References

{{Reflist, 2

External links

Description of project
on TenneT website (in German).
Factsheet: HVDC Platform Helwin 1

website.
HelWin 1 HVDC system
CIGRÉ Compendium of all HVDC Projects. Electric power transmission systems in Germany HVDC transmission lines Electrical interconnectors in the North Sea