Europe | March 12, 2025

First new Dinorwig electricity cables powered up

The first of three new sets of high-voltage electricity cables connecting Dinorwig hydroelectric power station in Gwynedd to National Grid’s transmission network has been energised.

 

Image for illustration purposes

UK: Engineers from National Grid, alongside Morgan Sindall Infrastructure and Siemens Energy, have reached a key milestone in the Dinorwig to Pentir project, replacing aging cables installed in the 1970s.

Since autumn 2021, National Grid has been upgrading the 12 km connection between the 400 kV Dinorwig substation, located within the same mountain as Dinorwig Power Station, and the 400 kV Pentir substation. The first new circuit, consisting of three 12.2 km cables weighing around 1,500 t, has now been installed under roads, fields, and inside Dinorwig.

Each new circuit follows a different route from the original cables, ensuring uninterrupted clean power transmission during the upgrade. The project is essential for futureproofing the UK’s energy network and maintaining reliable electricity supplies as demand rises. Work is ongoing to complete two additional circuits.

Alongside new underground cables, major upgrades are also underway at Dinorwig substation, a critical part of securing a reliable grid connection. Despite challenges such as hard rock and extreme weather, the first circuit has been successfully energised.

Peter Kirk, Managing Director – Energy at Morgan Sindall Infrastructure, emphasised the project’s role in strengthening the UK’s power network and supporting net-zero goals. ENGIE, the 75 % owner of First Hydro, which operates Dinorwig, also highlighted the upgrade’s importance in delivering clean energy across the UK.

Additionally, National Grid is taking environmental measures, including installing acoustic barriers in cable tunnels to protect bat habitats.

Dinorwig Power Station, with 16 km of underground tunnels, plays a crucial role in stabilising the UK’s electricity network, providing fast-response power when needed.

Source: National Grid