All T-pylons for Hinkley connection now ‘fully wired up’ 

All of the T-pylons for the £900 million project to connect Hinkley Point C to the power grid are now “fully wired up”, National Grid has announced.  

The 400kV connection spans 57km between the company’s existing Seabank substation in Avonmouth and its new Shurton substation at the site of the nuclear plant being built by EDF in Somerset.  

It comprises 48.5km of overhead lines – mostly using the new T-pylons – and 8.5km of underground cabling through the Mendip Hills Area of Outstanding Natural Beauty. There are shorter sections of traditional lattice pylons at either end of the route at Shurton and Avonmouth – the latter to ensure safe height over the Port of Bristol. 

In 2011, the T-pylon was chosen as the winner of an international competition to come up with a more visually appealing alternative to the old lattice design, which had not been updated since the 1920s. The first T-pylon was installed near East Huntspill in Somerset in September 2021. 

Each pylon supports a total of 12 conductors on two diamond-shaped insulators hung from either side of the main T-shaped structure. National Grid and its contractor Balfour Beatty have installed 460km of cable, weighing almost 1,300 tonnes, between the 116 T-pylons for the Hinkley connection. 

The wires were installed in sections of up to a dozen pylons at a time – a job that can take two weeks per segment. The first section was completed in March 2022.

The conductors were transported to each stringing site on large drums weighing up to seven tonnes, before being hoisted into place using steel braided guide ropes winched through circular running blocks suspended from the insulators. The last wires were fixed into place on a row of pylons near Yatton.  

In Spring last year, National Grid closed a section of the M6 several times to install T-pylon wires over the motorway.

Steven Haskayne, project director for National Grid, said: “With the T-pylons fully strung, our Hinkley Connection project is really starting to take shape. It’s a proud moment for all the teams involved, from our National Grid colleagues to our contractors, all of whom have helped us reach this milestone safely and on schedule. 

“We’re grateful to all of the local communities we’ve been working alongside for their patience as our project team continues its work, which is moving us closer to a resilient and secure low carbon energy supply for millions in the region.” 

An initial section of the route, including 36 T-pylons, a new National Grid substation at Sandford and the underground cables through the Mendip Hills were energised in March last year. The remaining T-pylons will all be energised by the end of 2024.  

As part of the project, National Grid is also removing 67km of existing overhead lines and old lattice pylons – 249 in total – from the Somerset landscape.  

Over 30 pylons running parallel to the new underground section in the Mendip Hills are already being taken down, which will leave the landscape pylon-free for the first time in nearly a century. 

Earlier this year, a survey revealed that the majority of the public would welcome an increase in their energy bills to cover the costs of installing T-pylons over traditional structures.