Overnight closures on A55 in Flintshire for National Grid electricity line upgrade

National Grid is starting work to upgrade 30 kilometres of overhead electricity transmission line in North Wales, between Connah’s Quay substation and Bodelwyddan substation in Denbighshire.

The project is part of a wider programme of circuit upgrades across the UK designed to speed up connections to the electricity transmission network and support a secure, affordable, and low-carbon energy system.

The upgrade will not involve replacing, moving, or building new pylons.

National Grid plans to invest £3.2 billion in Wales between 2026 and 2031 to maintain, upgrade, and develop the electricity network.

As part of the work, the A55 will be closed overnight in both directions between Junctions 31 and 32A on four dates this year to enable safe access where the overhead line crosses the highway.

The closures are:

9:30pm Monday 14 July to 5:30am Tuesday 15 July

9:30pm Wednesday 3 September to 5:30am Thursday 4 September

9:30pm Monday 6 October to 5:30am Tuesday 7 October

9:30pm Monday 27 October to 5:30am Tuesday 28 October

A temporary diversion via the A5026 will be in place during these closures.

The work involves erecting two scaffold structures on either side of the A55 with netting over the carriageway to safely replace wires crossing the road. This technique allows the highway to stay open during the day, minimising disruption to road users and local residents.

James Heywood, Project Manager at National Grid Electricity Transmission, said: “We’ve worked hard to try and minimise any disruption for road users, and we appreciate the cooperation and understanding of the community as we carry out these essential upgrades. Our Connah’s Quay to Bodelwyddan refurbishment project is an important part of our work to maintain the reliability of our electricity network and connect low carbon energy in the region.”

Preparatory work began in September 2024, with the main upgrade phase starting in July 2025. The existing overhead line components are nearing the end of their 60-year operational lifespan and need replacing to ensure continued reliability.

National Grid expects to complete the entire project by December 2026.

For more information, visit: https://www.nationalgrid.com/electricity-transmission/network-and-infrastructure/infrastructure-projects/connahs-quay-bodelwyddan#English

The project involves refurbishing 30km of high-voltage overhead electricity lines between Connah’s Quay (Flintshire) and Bodelwyddan (Denbighshire) to increase capacity and enable more clean energy connections across Wales and England.
The upgrade is part of a national programme to keep the electricity transmission network resilient, affordable, and supportive of the UK’s net zero transition.
Work is being carried out under National Grid’s permitted development rights, meaning no full planning permission is required, though they coordinate with bodies like Natural Resources Wales and local councils for specific licences and road closures.
Preparatory activities completed since 2024 include vegetation clearance around pylons, widening narrow access roads (“bellmouth widening”), installing scaffolding and temporary trackways to enable safe work.
The main construction phase starts July 2025 and runs until December 2026.
The work involves replacing all wires (conductors and earth wires) and associated insulators and steelwork on the pylons. Advanced technology allows reducing wires per pylon arm from four to three while increasing power capacity.
Wire replacement is done by cable pulling, with sections typically 10 pylons at a time, using pulling and tensioning sites.
Temporary scaffolding and netting are used to install cables safely over obstacles like roads, railways, and rivers.
The refurbished lines will appear almost identical visually but carry more power with fewer wires.
Road closures and increased construction traffic will occur at times, with advance notice to residents and businesses. Temporary footpath closures may also happen where overhead lines cross public rights of way.
National Grid is working with contractors MGroup to deliver the project and with local electricity operator SP Energy Networks to minimise supply disruption.
Working hours are generally weekdays 7am to 6pm, subject to change.
Environmental surveys and assessments have been completed to reduce local impact, with cooperation from landowners and regulatory bodies.
Contact for queries: [email protected] or 0800 138 5409 (9am–5:30pm weekdays).

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