What's happening now?
National Grid is carrying out work at Penrhos to construct a new Gas Insulated Substation on the former substation site, alongside the replacement of approximately three kilometres of existing underground electricity cable that previously connected into the site. This work is needed to keep the electricity network safe and reliable, and to enable new customers to connect to the electricity transmission system.
Early works have included surveys, ground investigations and site preparation. The main construction phase is due to start in summer 2026. Work will take place on the substation site and along the existing cable route.
The substation site is to the south-east of the former Anglesey Aluminium site. The cable route starts at the substation and runs broadly alongside the A5, towards Valley and just beyond Gorad Road. Along this route, we will remove and replace sections of the existing cables with new infrastructure. To do this, we will need temporary access points, known as bellmouths, as well as the use of temporary tracks and compounds to support construction.
Latest updates
Main substation works
Works at Penrhos Substation are continuing to make good progress, taking full advantage of the favourable weather conditions. The foundation bases for the substation have now been installed, and formwork is in place for the substation building basement. The team is now preparing for the next stage of construction, including the concrete pour planned towards the end of July. Images of our progress on site can be found below.
Gorad Road and A5 east of Causeway - bellmouth installation
Bellmouth works remain temporarily paused while environmental investigations continue, following the identification of a potential protected species in a nearby pond. We are continuing to work with Natural Resources Wales (NRW) to agree appropriate mitigation.
Stanley Embankment – cable removal
Cable removal works along the causeway are progressing well, with approximately 250 metres of cable removed to date. Works are continuing as planned, with completion scheduled for 20 November 2026.
Latest substation works (pictured)
How will these works affect me?
You may notice more activity in the area while we carry out construction, including construction vehicles, workers on site and temporary changes to traffic arrangements.
To keep people safe, we will need temporary traffic management at some points during construction. This may include traffic lights, lane closures and, in some locations, road closure. These measures will be introduced in stages across locations and will be designed to minimise disruption as much as reasonably possible.
We will continue to provide advance notice of key activities and keep you informed as work progresses, so you can plan ahead. Our project team will also be available to answer any questions.
Contact the team
If you have a question, you can contact us in the following ways:
Email us: [email protected]
Call us: 0808 303 0570