Electricity pylons (or towers) have been part of the British landscape for almost 100 years, but how much do you really know about them? Here we bring you 12 facts you never knew about these iconic steel structures.
Pylons are used to support electrical cables that transmit high-voltage electricity from where it’s generated, such as a power station or wind farm, through the energy system to our homes and businesses.
Electricity comes out of a power station at a low voltage, around 10-30 kilovolts. It then passes through a ‘step-up’ transformer at a transmission substation to create high-voltage electricity – up to 400,000 volts – which travels around National Grid’s electricity network. Increasing the voltage allows for greater efficiency with less energy loss. ‘Terminal’ towers are located at each end of the route, while tension or angle towers enable the route to be realigned if necessary.
|Did you know? While people call them pylons in the UK, they’re more correctly called suspension, tension or transmission towers. To complicate things, in the US ‘pylons’ are traffic cones.|
Insulators made of porcelain or toughened glass support the overhead high-voltage cables and keep them away from the unearthed towers.
The voltage of the electricity in the transmission cables (lines) is too high for use in everyday appliances, so a ‘step-down’ transformer in a substation is used to lower the voltage and bring it down to a useable level.
Distribution Network Operators transport the lower-voltage electricity through their own network of power lines and underground cables, to supply our homes and businesses.
In Ancient Egypt, pylons were the impressive obelisk-shaped towers on either side of the doors to temples. Egyptology was all the rage in the Twenties, after the discovery of Tutankhamun’s tomb and the boy king mummy in 1922. And this was the decade when the first steel pylons were erected and they eventually became the gateways to electricity for everyone.
But the Central Electricity Board’s new transmission grid didn’t begin operating until 1933, when it was run as a series of regional grids. The grid became a truly national system in 1938, a whole 10 years after that first pylon was erected.
Leading architect Sir Reginald Blomfield often gets the credit for the ‘lattice’ design, which was intended to be more delicate than the brutalist structures used in Europe and the United States. But the winning design, which still strides across our landscape today, was submitted to the competition by the Milliken Brothers, an engineering company based in the US, and chosen by Blomfield, designer of London’s Lambeth Bridge.
The basic latticed A-frame structure has remained the same for over 100 years, with adjustments for higher voltages requiring longer insulator strings and landscape requirements like lower heights near airfields or huge towers to cross rivers. (See no. 10 below for the world’s tallest pylons.)
This new shorter, sleeker pylon design was chosen from 250 entries in an international competition organised by National Grid, the UK Government and the Royal Institute of British Architects in 2011.
The winning T-shaped pylon comes from Danish firm Bystrup and measures 114ft (35 metres) tall. It’s about 50ft shorter than the traditional steel lattice structure, but can still transmit 400,000 volts.
The first operational T-pylons will bring low-carbon energy along a 35-mile route from Hinkley Point C power station to six million UK homes and businesses in the South West.
There are over 7,000 route kilometres (or over 4,300 miles) of high-voltage overhead lines in England and Wales.
Also, tall pylons mean the wires can easily straddle roads, rivers and railway lines. As a general rule of thumb, National Grid’s pylons are a minimum height of 118ft (36m).
As overhead lines are normally bare (uninsulated), it’s important to make them as high as possible to ensure nothing gets too close to them. You should never climb or attempt to get near to overhead lines, as this has the potential to cause severe shocks, burns or even death.
You may have wondered about this as you spot birds ranked along power lines without any seeming effect – why aren’t they electrocuted?
Birds don't get electrocuted on power lines because electricity does not move through their bodies. When the bird sits with both its feet on the electrical wire, its legs have an equal electrical potential, so the electricity will not move through its body. The bird isn’t touching the ground or anything in contact with the ground, so the electricity stays in the power line.
Built in 1965, the two towers are 623ft tall (190 metres) – taller than the BT Tower – and positioned at Botany Marshes in Swanscombe, Kent and West Thurrock in Essex.
This giant pylon carries high-voltage power cables between Jintang and Cezi islands in the eastern province of Zhejiang, China and was completed in 2019.
When the UK national electricity network expanded in the 1950s and 1960s to meet post-war demand, the priority was achieving nationwide electrification as quickly and cost-effectively as possible. Now National Grid is working to erase the impact of pylons and overhead lines in some of the country’s most beautiful landscapes, by constructing electricity tunnels underground through the Visual Impact Provision Schemes. Working closely with local environmental organisations and councils to ensure minimal impact on the environment, construction has begun in Dorset, while the Peak District and Snowdonia now have full planning approval.
Writers Rudyard Kipling, author of The Jungle Book, and John Maynard Keynes wrote to The Times complaining of ‘the permanent disfigurement’ of our landscape. But a group of poets led by Stephen Spender were so inspired by the metal pylon march they called themselves The Pylon Poets.