National Grid Begins Major Power Line Upgrade Between Dorset and Southampton

National Grid is set to undertake a major refurbishment programme on a key section of the UK's electricity transmission network, replacing overhead power lines across a 40km route between East Dorset and Southampton.

The project, which will be delivered by Balfour Beatty, forms part of National Grid’s ongoing investment in strengthening and modernising critical energy infrastructure as electricity demand continues to increase.

115 Pylons Included in Upgrade Programme

The scheme will cover the transmission corridor running between Mannington substation in East Dorset and Nursling substation near Southampton.

A total of 115 pylons will undergo works as part of the programme, which is scheduled to run between June and November 2026.

The primary focus of the project will be the replacement of existing conductors — the wires that carry electricity along overhead transmission routes. The process, known as reconductoring, will see ageing equipment replaced with modern alternatives designed to improve long-term performance and reliability.

Alongside the wire replacement works, engineers will also refurbish steel structures and associated fittings across the route.

Improving Network Resilience

National Grid says the investment is aimed at enhancing the resilience of the electricity network while helping prepare the system for future increases in demand.

As the UK continues to transition towards greater electrification of transport, heating and industry, transmission infrastructure is coming under increasing pressure to carry larger volumes of power across the country.

The company believes the refurbishment will help ensure the route continues to operate safely and efficiently for decades to come.

Importantly, National Grid has confirmed that no disruption to electricity supplies is expected during the course of the works.

Building on Earlier Investment

The latest phase follows a previous programme of upgrades completed along the route in 2023.

Preparatory works are already underway, with Balfour Beatty establishing temporary access routes and preparing individual pylon locations ahead of the main construction activity.

The contractor will oversee the delivery of the refurbishment programme on behalf of National Grid throughout the six-month project.

Supporting Future Energy Demand

Stephen Fedzin, Senior Project Manager at National Grid, said the transmission line has played a vital role in supplying electricity across the region for many years and that the latest upgrades will help maintain its reliability well into the future.

He explained that the works form part of a wider national programme designed to maintain and enhance the infrastructure required to support communities and businesses across the UK.

The investment aligns with National Grid’s broader strategy of upgrading transmission assets as part of the country's transition to a lower-carbon energy system.

Major Equipment Delivery to Mannington

Separately, National Grid has also completed the delivery of a new 120-tonne supergrid transformer to Mannington substation.

The transformer was transported from Poole Harbour on 23 May by specialist haulage contractors and travelled approximately 37km under police escort.

The installation forms part of wider enhancement works at the site and represents another significant investment in the region’s electricity infrastructure.

As demand for electricity continues to grow, projects such as the Dorset-to-Southampton refurbishment programme are expected to play a crucial role in ensuring the UK's transmission network remains capable of supporting future economic growth, energy security and decarbonisation objectives.