National Grid ‘strings’ wires onto world first pylons

National Grid has installed overhead wires onto the first of its redesigned T-pylons as part of a £900m connection project carrying low carbon electricity from Hinkley Point C nuclear power station in Somerset.

The Hinkley Connection project comprises 116 new T-pylons along a 57km stretch between Bridgwater and Portbury, delivering low carbon energy from Hinkley Point C to six million UK homes and businesses.

After pylon installation began in September near East Huntspill, project engineers have now added overhead wires – or conductors – to 36 of 48 completed pylons in place between Woolavington and Loxton.

Wire installation – or “stringing” – will begin on the 12 remaining structures between Bridgwater and Woolavington in April.

All 48 T-pylons will be energised in October with construction of the remaining 68 Connection project pylons to begin north of Sandford before the end of the year – with stringing slated for 2023.

The project will also see the removal of 249 traditional pylons Bridgwater and Avonmouth, and the new connection being forced underground through the Mendip Hills area of outstanding natural beauty.

High-wire act

The T-pylon design by Danish firm Bystrup – which was selected from more than 250 entries into a competition run by the Royal Institute of British Architects and the then Department of Energy and Climate Change in 2011 – features a single pole, T-shaped cross arms, and earring-like diamond insulators to hold overhead wires.

The first amendment to the traditional lattice pylon design in nearly a century, T-pylons are 35 metres high, a third shorter than their predecessor, and have a smaller footprint using less land.

The stringing process to install wires on them sees conductors transported to site on large drums, weighing up to 7.5 tonnes and 2.5m high.

Teams of engineers then pull a steel braided rope between sections of up to 12 T-pylons through circular running blocks suspended from the diamond-shaped insulators. The heavier conductors are then attached to the rope via a rectangular headboard, which is then pulled back through the running blocks using large winches.

The span of cables between each T-pylon is up to 360m with conductors installed in sections of up to 12 T-pylons at a time. Each section takes around two weeks to string.

‘Significant milestone’

According to National Grid, the Hinkley Connection Project will be ready to connect six million homes and businesses predominantly across the south west of England with low-carbon electricity generated by Hinkley Point C and other sources of low carbon energy in 2024.

“We’re immensely proud to have reached this significant milestone on the Hinkley Connection Project,” James Goode, National Grid’s project director said.

“National Grid is at the heart of the transition to net zero and the conductors we are installing today will carry low carbon electricity onto the network for millions of people across the UK to use for years to come.”

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