What is the Western Link project?
Why is this project needed?
The Western Link project involves constructing a high voltage direct current cable that will help to bring renewable energy from Scotland to homes and businesses in England and Wales.
Elsewhere in the UK, electricity is transmitted by alternating current. The Western Link project therefore incorporates a converter station at each end of the link to change the electricity from direct current to alternating current to enable it to be used within the existing national grid transmission system. The project includes:
- A converter station at Hunterston, North Ayrshire.
- Approximately 4km of high voltage direct current cable to a ‘landfall’, where the subsea cable comes ashore, at Ardneil Bay.
- A subsea marine cable approximately 385km long from Ardneil Bay to Leasowe on the Wirral peninsula.
- An underground high voltage direct current able of approximately 33km through the Wirral peninsula.
- A converter station and an alternating current cable connecting it to the upgraded substation on National Grid’s site in Deeside, Flintshire.
How much electricity will be transmitted through the link?
The Western Link project will play a key role in helping the UK meet its renewable energy targets. The amount of renewable energy being generated in Scotland is increasing rapidly, but this cannot be transferred south because the existing electricity links are running at full capacity. A new link is therefore needed to allow the additional ‘green’ energy to come on line.
Why use a high voltage direct current cable?
The link is capable of transmitting 2,200 MW (megawatts) power – sufficient electricity to meet the immediate needs of around two million people, or a city four times the size of Liverpool.
Why is a subsea cable the preferred option?
We need to transfer around 2,200MW of power across several hundred kilometres to link the transmission network in Scotland with that in England and Wales, and a subsea marine HVDC cable is the best method of doing this because:
- It provides the most efficient and economic solution (in many cases the use of HVDC technology is relatively expensive and not efficient)
- DC circuits can transmit power more efficiently over long distances, on fewer cables than equivalent AC circuits
- The use of DC transmission makes long-distance subsea cable technically possible
- Subsea cables can be installed relatively quickly, with minimal disruption to local communities
What is the cable made of?
We selected a subsea cable from a number of options that we considered, including overhead lines and underground cables across mainland Britain. Taking into account the overall costs, potential impacts on local communities and potential environmental effects, we believe a subsea cable is the most appropriate solution.
Who is running the project and who is building the infrastructure?
The cable is a traditional design for high voltage cables and will have copper conductors and special paper insulation wound around the core. The cable will also have an outer plastic cover.
When did construction start and when will the link be completed?
National Grid and ScottishPower Transmission have joined together to deliver the project. We have employed Prysmian to install the underground and marine cables, and Siemens to build the converter stations at either end of the cable, in Hunterston and Deeside.
Why can't the cable be routed through the River Dee?
We started cable installation in spring 2013 and anticipate that power will flow along the link in 2017.
Can the cable be operated both ways?
In planning, designing and constructing the Western Link we aim to minimise disturbance to communities and the environment.
One of our initial ideas was to route the cable through the Dee Estuary as it is the most direct route, but this was not feasible. The movement of the sand on the bed of the river and the use of the estuary by shipping increased the possibility that the cable would not work properly or would be damaged. Also, the Dee Estuary is classed as an area of high environmental importance.
How do you reinstate the land above the underground cable and how long does reinstatement take?
Although the reason for constructing the Western Link is to take renewable energy from Scotland to homes and businesses in England and Wales, it is capable of operating in the opposite direction, bringing power from England and Wales to Scotland, if needed.
During reinstatement we will remove all surplus materials from site, remove the temporary haul road, install post construction drainage, and reinstate topsoil and any fencing, walls or hedges as appropriate. Reinstatement is a critical activity that must be completed in the right conditions. The process is very dependent on the weather and overall can take a few months from when we start in an area. Although we won’t necessarily be working on site all the time, when we are, there will be an increase in activity to and from our work area.