Construction of a new Gas Insulated Substation (GIS) and associated cable replacement
National Grid Electricity Transmission (NGET) is planning to construct a new Gas Insulated Substation (GIS) at our former substation site at Penrhos. The original substation that served the old Anglesey Alluminium plant was decomissioned in 2009 and the main structures were removed in 2024.
Penrhos substation works
As the Transmission Network owner in England and Wales, NGET has identified the need to construct a new GIS as part of our obligation to connect customers to the network.
The plans include the construction of a new GIS and the replacement of approximately 3km of existing underground cable that connected into the former Penrhos substation.
The Isle of Anglesey County Council (IACC), as the Local Planning Authority, has confirmed that the plans are Permitted Development under the Town and Country Planning (General Permitted Development) (Amendment) (Wales) Order 2019. As such, there is no requirement for NGET to apply for planning permission for the works.
In advance of starting work on the site we will be undertaking ground investigation (GI) surveys during April and May 2025 to assess ground structure and condition with the results used to inform the final project design. This includes surveying the route of the underground cable that currently connects to the former substation.
Timeline
- February 2025 - Topography surveys and preparatory work began on site
- April-May 2025 - Ground investigation works commenced (for approximately 6 weeks)
- Winter 2025 - Works commences on the construction of the GIS
- Spring 2026 - Works commences on the cable replacement
- Spring 2027 – Works complete on the GIS and cable replacement
Have your say
National Grid is committed to engaging with communities at every stage of the project. Our dedicated community relations team works with local residents, businesses and community groups to ensure our work causes as little disruption as possible. Prior to the beginning of the main works, we will be issuing a newsletter to local residents and stakeholders, so that you can learn more about our plans and ask any questions.
Contact us
If you have any further queries, please do not hesitate to contact our community relations team on 0800 066 8941 (Monday – Friday, 9:00am – 5.00pm) or email [email protected] or you can write to us using our freepost address:
Freepost: GIVEYOURVIEW
Email us: [email protected]