Connecting The World's Largest Offshore Wind Farm To The UK Grid

Nexans' high-voltage subsea power cable
Each Nexans high-voltage subsea power cable could weigh as much as 7,000 tons.

Nexans, the worldwide leader in the cable industry, has won a contract worth approximately 100 million Euros to design, manufacture, and supply the high voltage subsea power export cables that will connect the London Array wind farm to the UK grid. The contract was placed with Nexans by the consortium of DONG Energy, E.ON, and Masdar, which is currently building the world’s largest offshore wind farm in the Thames Estuary.

The London Array wind farm is being installed on a 233 km2 site located about 20 km off the UK coast. Construction is taking place in two phases: the first phase of 630 megawatts, consisting of 175 turbines, is expected to be completed and generating in 2012; the future second phase will add capacity to bring the total to 1,000 MW and will supply enough power for around 750,000 UK homes.

The power export cable contract comprises the design, manufacture, and supply of four 150 kV XLPE submarine power cables to be laid in parallel, each 53 to 54 km in length, with three copper core conductors with a cross-section of 630 mm2 for the main length and 800mm at each cable end. Nexans will deliver two of the cables in 2011, and two in 2012, all being delivered in single continuous lengths from Nexans’ factory in Halden. The cables will also incorporate fibre optic elements manufactured at the Nexans factory in Rognan, Norway. In addition, the contract also includes the cable accessories such as repair joints and terminations.

“This new contract is the result of several years of Nexans’ involvement in the offshore wind sector in general and in the UK in particular. We are happy to demonstrate once again with this major contract Nexans’ ability to provide key cable solutions for a better deployment of wind farm infrastructures,” says Krister Granlie, Managing Director of Nexans’ Umbilicals & Submarine High Voltage Business Group.

“World-leading schemes such as London Array demonstrate why the UK is currently regarded as one of the pace-setters in offshore wind energy, and we are very proud to be co-operating in this prestigious project with some of the key developers in this dynamic market,” says Frederic Vincent, Nexans CEO.

Over the past four years, Nexans’ share of the offshore wind farm market has tripled in size. Considering current political and financial incentive policies, particularly in Europe, this market should gain importance in the future.

In this market, Nexans offers complete turnkey solutions for its clients, from manufacturing in its specialized production unit based in Norway to installation using advanced, dedicated systems designed in-house. High voltage cables for typical offshore projects are usually produced in one single length of about 50 km long – which requires specific industrial know-how and manufacturing technology – and they can weigh up to 120 kg per meter of cable according to the conductor cross-section. A single cable can weigh up to 7,000 tons.

Over the past few years, Nexans has demonstrated its expertise through participation in many offshore wind farm projects worldwide: Barrow, Horns Rev, Lynn and Inner Dowsing, Wolfe Island, etc. Recently, the Group has also proved its technological commitment to the continued development of the offshore wind farm market by supplying and installing the submarine power cable for the world’s first floating wind turbine in Norway.

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