As National Grid’s innovative new pylon design reaches a significant milestone in its development, David Wright, Director of Electricity Transmission, explains what else lies ahead for Britain’s high-voltage transmission network.
Designed to a T
“The T-pylon offers a modern, sleek and slender alternative to traditional designs. It is designed so that we can route overhead cables by following the contours of the land.”
David Wright, Director of Electricity Transmission, National Grid.
There are more than 88,000 pylons in the UK, including 22,000 on National Grid’s main transmission network in England and Wales.
Source: National Grid
Love them or hate them, the steel lattice electricity pylon has been a familiar sight since the first was erected near Edinburgh in 1928. Now, the country has reached a significant milestone with the inclusion of National Grid’s innovative T-pylon in the public consultation on the proposed 400,000-volt connection between Bridgwater and Seabank in Somerset, which will connect up the new Hinkley Point C nuclear power station.
The T-pylon is something of a new departure for us. For 85 years we have only ever erected steel lattice pylons, and over that time I think we have done a pretty good job at protecting the British countryside with pylon systems that do not look as messy and confused as they do in some countries.
At National Grid we want to build on our work in preserving the nation’s natural beauty by further minimising the visual impact of overhead cables.
The T-pylon was the winner of an international competition to find a pylon design that was fit for the needs of the 21st century. Designed by Danish architects and engineers Bystrup under contract to National Grid, it is lower than the equivalent steel lattice type, and so has the potential to reduce the impact in some landscapes.
Designed to a T
The T-pylon offers a modern, sleek and slender alternative to traditional designs. It is designed so that we can route overhead cables by following the contours of the land. Instead of sudden changes in direction that have characterised some routes with lattice pylons, the T-pylon helps us move towards more sweeping curves that follow the landscape.
The T-pylon is shorter, too. A 400,000 volt lattice pylon is typically up to 50-metres high, while the T-pylon stands about 36-metres high.
The lower height of the T-pylon is possible because of the new way the cables are held in place. Instead of being attached to three arms as on a lattice pylon, the T-pylon uses an innovative diamond arrangement to carry the cables off one arm in a much smaller space. This means the pylon height is lower.
However, the T-pylon will not be used everywhere. In urban landscapes or where other lattice pylons exist, the old design may be more appropriate. And we are certainly not proposing the replacement of all existing pylons with the T-pylon, as this would be prohibitively expensive. There is, however, a fund set aside to reduce the visual impact in areas such as National Parks, but this is more likely to be done by selective use of underground cables rather than by replacing pylons.
We have worked closely with Bystrup to develop a family of T-pylons and erected trial units to test loading both in terms of weather conditions and electricity capacity.
But we are not just focusing on pylons. We are also looking at other technologies for innovation, for example underground cables.
The inclusion of the T-pylon in the Hinkley Point consultation is undoubtedly a significant milestone for us, and a tremendous achievement for everyone involved with the project. But what else does the 21st century hold in store for our electricity transmission infrastructure?
First, we will need considerable investment in our electricity infrastructure. Many of the assets in use today were built in the 1950s and 1960s. Some of them are reaching the end of their useful lives and need replacing, refurbishing or more extensive maintenance.
Also, with the move to a low-carbon economy, the locations for power stations are changing. The traditional ring of coal-fired generation in the centre of England is giving way to coastal generation, such as the Hinkley Point C nuclear plant. The areas most suited to wind-powered generation are in Scotland, and offshore in the North and Irish seas. Connecting up these, together with new nuclear and possibly future shale gas sites, will need new developments within our infrastructure.
National Grid is listening
We are very much in listening mode on this subject. By listening to people across the UK, we want to find new, collaborative solutions rather than having people disagree with us when we come up with our proposals.
From our initial strategic options report, through to publishing our preferred corridor for a project, we want genuine public consultation, and to hear the views of local people.
Going underground is the most requested solution, but this is an option that brings with it vastly increased costs. For example, at the voltages and capacity required by many of the new lines we need to build, the cost of going underground is typically £16 million per kilometre dearer than overhead cables. Of course, all of these are extra costs that would ultimately find their way through to customers’ bills.
But we are listening, and as part of our consultation we do propose underground cables in certain areas. For the Hinkley Point route, nearly five miles are proposed to be underground through the Mendip Hills, an area of Outstanding Natural Beauty. We are also currently considering what pylon design should be used in various locations along the rest of the route.
We love the countryside just as much as anyone else. Our strategy for transmission is therefore all about minimising the visual impact of our assets on our landscape while still providing the infrastructure we need to meet the country’s future electricity needs in a cost effective way.
T-pylon designers Rasmus Jessing and Erik Bystrup talk about the new pylon design.
The six pylon designs shortlisted in the competition.
Reduced EMF from T-pylon.
A family of T-pylon designs enable turning corners.
Hinkley Connection Project Website