Key milestone as first new Dinorwig electricity cables powered up
- National Grid switches on new high voltage electricity cables as part of its Dinorwig to Pentir project
- Scheme will help futureproof vital infrastructure carrying clean electricity from ENGIE-owned Dinorwig power station
- Work has also involved safeguarding the habitats of rare bat species in Dinorwig’s cable tunnels
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.
Engineers from National Grid, and contractors Morgan Sindall Infrastructure and Siemens Energy, reached the key milestone as part of the Dinorwig to Pentir project to replace cables originally installed in the 1970s, and which are now coming to the end of their operational life.
Dinorwig power station is owned and operated by First Hydro, a company which is 75% owned by ENGIE.
Since autumn 2021, National Grid has been upgrading the 12km connection between its 400kV Dinorwig substation – which sits inside the same mountain as the power station, transmitting its electricity to the grid – and its 400kV Pentir substation.
The first new circuit, comprising three 12.2km cables each made from 14 sections joined together and weighing an estimated 1,500 tonnes, has been installed under sections of the A4086 and A4244, in nearby fields and inside Dinorwig.
Each new circuit takes a different route from the original cables, ensuring the existing connection can remain in service and continue transmitting vital clean power from Dinorwig while the upgrades take place.
National Grid’s project is a necessary upgrade to the transmission network to ensure the reliability and security of electricity supplies from ENGIE’s First Hydro site to the local area and beyond in the decades to come, as demand for electricity rises. Work is ongoing to complete two other new circuits as part of the scheme.
Alongside installing the new underground electricity cables, National Grid is also making good progress on major upgrades to its Dinorwig substation.
While the project is hidden from view within the mountain, the complex engineering work is an equally essential part of creating the new, secure and reliable connection between the power station and the electricity network.
Phil Rose, National Grid’s Lead Project Manager for the Dinorwig to Pentir cable replacement project, said:
“Completing the first of our three connections marks a really significant milestone in this crucial project to futureproof the infrastructure carrying clean power from Electric Mountain.
“It’s also a fantastic achievement for the team despite some very difficult conditions, with extremely hard rock and unprecedented rainfall challenging our progress at times.
“We appreciate the cooperation and understanding of the local community whilst the work takes place, and want to thank everyone locally for their continued patience while this essential work progresses.”
Peter Kirk, Managing Director – Energy at Morgan Sindall Infrastructure, said:
“Energising circuit 3 at Dinorwig-Pentir creates a more resilient power network for the UK. This improvement will enable the network to better handle sudden changes in power demand and unexpected outages, and also supports the UK’s net zero carbon goals by providing vital infrastructure needed for renewable energy sources.
“The project’s success is only possible because of close collaboration between National Grid, Morgan Sindall Infrastructure and the other project partners. Thank you and congratulations to everyone involved.”
Delphine Cherel-Sparham, Managing Director of ENGIE Flexible Generation UK, said:
“As owner and operator of Dinorwig power station, ENGIE is excited to see the first new high voltage cables energised as part of the Dinorwig to Pentir project.
“This milestone is key to futureproofing our infrastructure and ensuring that the clean energy from Dinorwig continues to power communities across the UK. The collaboration between project partners and the First Hydro team has been essential to the successful and safe delivery of this project.”
As part of its work at Dinorwig, National Grid is also safeguarding critical bat habitats in the cable tunnels, which has included installing permanent acoustic barriers alongside roosts to reduce disruption during construction.
Dinorwig hydroelectric power station is made up of 16km of underground tunnels deep below Elidir Fawr mountain in Gwynedd. It is a vital part of the electricity network in Wales and England, providing fast-response power generation to help stabilise demand on the transmission network.
