Rhigos substation, Wales

We were completing extension works to facilitate a 299MW connection for a new Open Cycle Gas Turbine (OCGT) power peaking plant, which will help support Great Britian’s energy security. 

The power station will provide back-up to other sources of electricity, including wind turbines and solar farms and help the UK transition to a lower carbon economy. It’s estimated that the power station will generate enough instant electricity to power 150,000 households. 

The main civil works included:

• 12,000m³ cut and fill exercise to reinforce, stabilise and build up the ground around the existing substation.
• The installation of 282 piles to help support the ground build up works.
• The installation of 52 new foundations to support the new equipment structures, including the use of 35 x pre-cast foundation bases to help streamline the programme.
• Installation of a new duct and trough network for the underground multicore and power cables which provide the power and comms to all of the new equipment.
• Extension of the existing drainage network and extension of the existing substation electric fence.  
  The main mechanical & electrical (M&E) works included:
• The installation and commissioning of the new Air Insulated 400kV switchgear (AIS).
• A new mechanical interlocking scheme and new below and above ground earthing network.
• A new mechanical interlocking scheme and new below and above ground earthing network.

There were several challenges faced by our team during the project, including stockpiling the spoil from the civils cutting exercise, due to the ground being classed as contaminated, which were later used as part of the landscaping reinstatement plan. 

We made the decision to use the pre-cast foundation bases for 70% of the switchgear foundations in order to gain some time back and streamline the civil foundation installation programme. 

The was extremely well received by the client due to the clear programme benefits gained from the use of the pre-cast bases.  

Our team successfully connected the new 400kV bay extension onto the existing National Grid 400kV network in December 2024, after a 30-month detailed design and installation programme. 

The works are in line with the power station connection requirements with the final commissioning works left to complete in early 2025. 

We hope the green space created as part of the landscaping reinstatement plan will provide a new habitat for local wildlife to thrive.