Dinorwig pumped hydro station gets cable upgrade

Built in the 1970s, Dinorwig sits inside the mountain Elidir Fawr in Snowdonia national park in Gwynedd, north Wales. The pumped hydro facility can deliver a maximum power of 1,728MW and has a storage capacity of around 9.1GWh.

The Dinorwig to Pentir project is replacing cables from the power plant to National Grid’s 400kV Pentir substation, around 12km away. 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. The project was carried out by engineers from National Grid and contractors Morgan Sindall Infrastructure and Siemens Energy

Each new circuit takes a different route from the original cables, allowing the existing connection to remain in service while the upgrades take place. According to the project partners, the scheme will help futureproof vital infrastructure carrying clean electricity from the ENGIE-owned Dinorwig power station, known locally as ‘Electric Mountain’.

“Energising circuit 3 at Dinorwig-Pentir creates a more resilient power network for the UK,” said Peter Kirk, managing director – Energy at Morgan Sindall Infrastructure.

“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.”

Dinorwig power station is made up of 16km of underground tunnels deep below Elidir Fawr, providing fast-response power generation to help stabilise demand on the transmission network. Alongside installing the new underground electricity cables, National Grid is also making major upgrades to its Dinorwig substation.

“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,” said Phil Rose, National Grid’s lead project manager on the scheme.

“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.”