Post date: Thursday, 16th February 2012

World-beating €1.1bn under-sea cable to connect England and Scotland

 
The Western HVDC Link

The Western HVDC Link will be the longest 2,200MW HVDC cable in the world, and the first to use a voltage level of 600kV.

While politicians talk of Scottish independence from England, a world-beating €1.1bn contract has today been announced to make the two countries even more interconnected.

The Western HVDC Link will be the first submarine grid interconnector ever that uses a high voltage direct current (HVDC), and is to join the Glasgow and Wirral areas along the bed of the Irish Sea. It is planned to be up and running by 2016.

No ordinary wire, this grid connection has two other claims to fame: it will be the longest 2,200MW capacity HVDC cable in the world, as well as the first to use a voltage level of 600kV (600,000 volts).

This will increase the link’s capacity and provide lower transmission losses.

The highest voltage level used to date has been 500 kV; Siemens says that raising the voltage level in the cable by 20% raises the amount of electrical capacity it can handle by the same amount, while still using the same diameter of copper in the cable, thereby reducing the cost of this expensive material.

Furthermore, the transmission losses over its 420km will be reduced to below 3% (including cable and converter losses). A conventional 400-kv A.C. connector would lose about three times this amount.

The project has been commissioned by the National Grid Electricity Transmission and its counterpart Scottish Power Transmission from Italian cable company Prysmian and the German company Siemens Energy, to bring renewable energy from Scotland and the Irish Sea to help England meet its 2020 renewable targets.

The order comprises cable installation along the route and construction of converter stations in Hunterston, in Ayrshire, and Connah's Quay on the Wirral peninsula on the Wales-England border.

Ignacio Galán, chairman of ScottishPower, said that the project should be seen "in the context of a vital upgrading of the UK electricity grid over the coming years, with the electricity grid between Scotland and England already running close to maximum capacity".

He said that ScottishPower expects to invest a total of £2.6bn between 2013-2021 on upgrading its transmission network in the UK.

"Overall, we are projecting investments totalling £12bn in the UK over the course of this decade, including major offshore wind projects around the country,” he added.

Nick Winser, executive director at National Grid, said: “This link will have a vital role of play in helping to address the problem of climate change.

"We are investing in an innovative solution using the most advanced technology. The benefits for consumers and electricity generators in being able to transport power in the most efficient way, will be felt for years to come.”

Round 3 windfarms

The Western HVDC Link will support the planned expansion of renewables such as offshore wind and marine power at sites that are far away from loads and where the amount of electricity produced can be dependent on weather conditions.

It will therefore help to meet the consequent challenge of balancing power generation and consumption within the grid.

Underground or submarine cables lengths of 80km or more are only possible with HVDC transmission technology because when A.C. lines reach this length the cable’s insulation serves as a capacitor and becomes charged, thereby absorbing most of the electricity.

Future wind farms will be far offshore due to the higher yield and because the near-coastal regions were already contracted out in rounds 1 and 2.

For round 3, with 32 GW of wind power, areas have been identified for wind farms that are between 40 and 200 km off the coast.

In the Irish Sea, the area is 'Zone 9', located between the Isle of Man and Anglesey.

"This order underscores our technological leadership in the HVDC field," said Udo Niehage, CEO of the Power Transmission Division of Siemens Energy.

“It will be the first subsea interconnector with a transmission capacity of 2200 megawatts – this equals the power output of two large-scale power plants,” he added.

The project was conceived in 2009 following an Electricity Network Strategy Group survey which identified a number of transmission reinforcements needed to enable renewable energy to be connected and secure the UK’s energy supplies.

Its report said the HVDC subsea link would be the most appropriate way to ensure that the additional energy generated in Scotland could be transmitted to the rest of Britain, because HVDC becomes more economic at longer distances.

Udo Niehage said that he foresees an expanding need for HVDC. “By 2020, I’m expecting to see new HVDC transmission lines with a total capacity of 250 gigawatts. That is a dramatic increase. In the last 40 years, we’ve only installed 100 gigawatts worth of HVDC transmission lines.

“Additional HVDC transmission projects will be awarded in Germany and Europe during this year.”

China, India, and Brazil in particular are also utilising the technology more and more, because their energy demand is growing rapidly and large distances must be bridged to ensure a supply of electricity from renewables projects.

Story: David Thorpe, News Editor

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