National Grid has energised the second of three new high-voltage electricity circuits linking Dinorwig pumped storage power station to the transmission network in North Wales, marking a further step in a long-term upgrade of critical grid infrastructure.
The milestone follows the commissioning of the first circuit in January 2025 and forms part of a programme to replace assets installed in the 1970s between Dinorwig and Pentir substation.
Dinorwig, located within Elidir Fawr mountain in Gwynedd, plays a key role in grid stability by providing rapid-response electricity generation. The facility is owned and operated by First Hydro, which is majority owned by ENGIE.
Since autumn 2021, National Grid has been delivering the upgrade in partnership with Morgan Sindall Infrastructure and Siemens Energy. The project aims to ensure that electricity from the station can be transmitted reliably for decades.
Mark Brindley, construction director at National Grid, said: “Switching on the second new circuit is a major step forward for this project. We’re strengthening a vital clean energy link in North Wales and ensuring Dinorwig can continue to power homes, businesses and communities for years to come.”
He added: “We’re immensely grateful for the continued patience and understanding of local communities as we push ahead with the final phase of this complex once-in-a-generation project.”
Alongside the cable works, reinforcement activity is continuing at Dinorwig substation, which is housed within the mountain. The upgraded installation includes a hybrid gas-insulated switchgear system combining SF6 and ‘clean air’ technologies, supporting efforts to reduce greenhouse gas emissions from the network.
Peter Kirk, managing director – energy at Morgan Sindall Infrastructure, said: “We’re proud to be delivering this important work in North Wales, helping to bring cleaner energy onto the UK national grid and strengthen the resilience of the network.”
He added: “Energising the second circuit is the latest success story of strong collaboration, as we apply an innovative approach to upgrading existing circuits and boosting capacity between the Dinorwig and Pentir substations in a challenging environment.”
With the second circuit now operational, work is focused on completing the third and final connection, alongside further upgrades at both Dinorwig and Pentir substations.
Delphine Cherel-Sparham, managing director of ENGIE Hydro UK, said: “It is fantastic to see the second circuit energised – another important step for Dinorwig’s future and enhanced reliability.”
She added: “As owner and operator, ENGIE is investing to extend the life of the station and is proud to be working with partners supporting its delivery; strengthening the flow of clean, flexible power from Wales to homes across the UK.”
The Dinorwig–Pentir scheme is separate from National Grid’s planned Pentir–Trawsfynydd upgrade, which aims to further strengthen the high-voltage network in North Wales to meet rising demand and connect new sources of low-carbon energy.
