Pylons – also known as electricity transmission and distribution towers – are the structural supports that have carried the UK’s network of high-voltage overhead power lines for nearly 100 years.
Today there are more than 90,000 transmission and distribution electricity pylons across Britain.
Pylons are used to support high voltage overhead lines – the electrical cables that transmit electricity all over the country through the electricity grid.
Electricity originally comes out of a power station at a low voltage of around 10-30 kilovolts. If it's being fed onto the transmission network, it enters a transmission substation where it passes through a supergrid transformer that 'steps it up' into high-voltage electricity – up to 400,000 volts. This ensures greater efficiency and less energy loss as it travels around the national grid.
The electricity eventually reaches another substation where a transformer 'steps it down' into more usable, lower-voltage electricity.
Local Distribution Network Operators (known as DNOs) – such as National Grid Electricity Distribution – transport this lower-voltage electricity through their own power lines and underground cables to supply homes and businesses.
Pylons are usually made of steel, due to its strength. To avoid the steel conducting an electrical current from the high-voltage cables into the tower, ‘insulators’ are used. These are usually made of materials that won’t conduct an electrical current, such as porcelain or glass.
As overhead lines are bare (uninsulated), it’s important that they’re high enough from the ground so neither human nor machine can come into contact with them.
The reason pylons are so tall is for safety purposes, so the overhead lines can’t be reached by the public and can easily straddle roads, rivers, valleys or railway lines without coming into contact with passing vehicles or people.
You should never climb a pylon or attempt to get near to overhead lines, as this has the potential to cause severe shocks, burns or even death.
Some people worry about electromagnetic fields (EMFs) from power lines having negative health effects and we take these concerns seriously.
Studies by independent scientific authorities, such as the World Health Organisation (WHO) and UK Health Security Agency (UKHSA), have been unable to establish any health risks from EMFs at the levels at which the UK’s network operates. These levels are reflected in guidelines set by government and met by all UK electricity infrastructure – including our own.
You might have noticed that pylons in the UK come in different sizes. This is because they carry different types of power line and they’re owned by different organisations.
The larger pylons – carrying 400kV and 275kV power lines –are owned by National Grid Electricity Transmission. They transmit electricity from where it’s generated (such as power stations or wind farms) to regional substations. This part of the electricity network is known as the ‘transmission network’ because it transmits power across the country.
The smaller pylons – which carry power lines of 132kV and lower –are owned by the DNOs. They carry electricity from the substations to our homes, businesses and anywhere else that uses electricity.
National Grid’s UK transmission pylons are a minimum height of 118ft (36m), while the tallest are 623ft tall (190m), crossing the River Thames between Essex and Kent – taller than the BT Tower in London, which stands at 620ft (189m) including its aerial rigging.
To make sure that the pylons and overhead lines that we’re responsible for are properly maintained and any defects are fixed, we use a few different methods.
We often use helicopters to carry out inspection work, as they can cover large distances and they don’t require access to the land surrounding our powerlines. We also have a fleet of drones, which allow us to look at parts of our network that are more difficult or costly to reach.
In the event that using a drone or helicopter isn’t feasible, we’ll use a manual ‘climbing assessment’, where our engineers will physically climb up the pylon themselves.Watch our engineer climb a pylon
The T-pylon is the first new design for UK electricity pylons in nearly
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 is about 50 ft shorter than the traditional steel lattice structure but can still transmit 400,000 volts. The overhead power lines it carries are suspended from a diamond-shaped ‘earring’.
The operational life of the new T-pylon is around 70-80 years.
The world’s first operational T-pylon construction project currently underway and is expected to be completed in 2026. This project will see 116 T-pylons installed along National Grid’s 57 km Hinkley Connection route. The route will connect low-carbon energy from EDF’s Hinkley Point C power station to six million UK homes and businesses.
Last updated: 13 September 2023
The information in this article is intended as a factual explainer and does not necessarily reflect National Grid's strategic direction or current business activities.