Construction of a new Gas Insulated Substation (GIS) and associated cable replacement
National Grid Electricity Transmission (NGET) is planning to build a new Gas Insulated Substation (GIS) at our former substation site at Penrhos. The original substation that served the old Anglesey Aluminium plant was decomissioned in 2009 and the main buildings were removed in 2024.
We are building the substation in response to connection requests for renewable energy and a new business development. NGET have a legal obligation to connect customers to our network when a connection is requested.
Penrhos substation works
The Isle of Anglesey County Council (IACC) confirmed that this work is classed as Permitted Development under the Town and Country Planning (General Permitted Development) (Amendment) (Wales) Order 2019. This means that planning permission is not required for the construction activities.
As part of the project, we will also be replacing approximately three kilometres of existing underground electricity cable that previously connected into the former substation.
Construction
Timeline
Below is our construction timeline:
- March 2026 - Site preparation complete
- July 2026 - Construction works start
- April 2028 - Cable system ready for energisation
- July 2028 - Substation ready for energisation
- Summer 2028 - All works complete
Contact us
If you have any questions about the substation project, please do not hesitate to contact our community relations team, by emailing [email protected], or by calling 0808 303 0570.