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High-voltage transmission tower with multiple power lines extending outward, set against a cloudy sky.

Morgan Sindall Infrastructure completes overhead line upgrade between Harker and the Scottish border

• Energy • 3 min read

Morgan Sindall Infrastructure has successfully completed upgrade works on overhead electricity transmission lines north of the Harker substation near Carlisle, delivered on behalf of our client, National Grid. These essential improvements strengthen a key cross‑border link that supports the reliable supply of power to communities and businesses across England and Scotland. 

This activity forms part of National Grid’s wider Harker upgrade project, within which includes the construction of new 400kV and 132kV indoor substations adjacent to the existing site. These upgrades will enable new network connections and help future‑proof the region’s electricity infrastructure for decades to come. 

The overhead line (OHL) works replaced existing circuits on two separate routes between Harker and the Scottish border with higher capacity wires, with an additional 12km OHL circuit also installed on existing pylons to help improve power flow and reduce congestion. 

More than 90km of overhead line has been replaced or installed in total – enough to stretch from Carlisle to Newcastle. 

To support the upgraded lines, existing pylons along each route have been refurbished and strengthened, with three new towers added and two older towers set to be removed which are no longer needed. 

Peter Kirk, Managing Director – Energy at Morgan Sindall Infrastructure said: 

“The upgrade of the overhead line is a great example of National Grid and Morgan Sindall Infrastructure working together to deliver essential improvements that will support local homes and businesses for years to come. We’re also proud to give something back to the community by helping to fund facilities that genuinely support the mental and physical wellbeing of local people.” 

Mark Brindley, portfolio director for northern regions at National Grid Electricity Transmission, said: 

“This overhead line upgrade is a crucial step in strengthening this crucial part of the network between Harker and the Scottish border. By working closely with our supply chain and minimising disruption to the local community, we’ve delivered a complex engineering project that improves reliability today and creates capacity for cleaner energy in the future.” 

The substation and overhead line upgrades, together with other projects in the region, will help increase the amount of power that can be carried between England and Scotland in future – an increasingly important link as more renewable generation connects to the grid. 

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