National Grid Launches North West London Upgrade to Strengthen Electricity Network
National Grid has officially launched its North West London Upgrade (NWLU), a major electricity transmission investment aimed at strengthening the region’s power network, increasing capacity and supporting the rapid growth in electricity demand expected across North West London and surrounding areas.
The large-scale programme is designed to reinforce critical transmission infrastructure stretching from the Sundon substation in Bedfordshire through Elstree in Hertfordshire and onward to the St John’s Wood substation in London. The project brings together a series of coordinated upgrades, including new substations, additional cable infrastructure, improvements to existing substations and reinforcement of overhead transmission lines.
By increasing the capacity and resilience of the network, the NWLU will help create additional headroom for new electricity connections while improving the reliability of power supplies for homes and businesses. The investment is also expected to help reduce electricity system constraint costs, supporting efforts to keep long-term energy costs under control for consumers.
Supporting North West London’s Growing Electricity Demand
Electricity demand is increasing rapidly across North West London as new housing, commercial developments, digital infrastructure and other energy-intensive industries expand. One of the most significant drivers is the continued growth of data centres, which require large amounts of reliable electricity to operate.
The NWLU will provide infrastructure capable of supporting new connections while ensuring that the existing electricity network can meet future requirements. In Hertfordshire, the programme will extend the existing 400kV Elstree gas-insulated switchgear (GIS) substation and construct a new 132kV Letchmore Heath GIS substation alongside it.
The new Letchmore Heath facility will enable the connection of five new data centres with a combined electricity demand equivalent to approximately 1GW. This additional capacity is expected to play an important role in supporting the digital economy while maintaining secure electricity supplies for existing customers.
The programme forms part of National Grid’s wider investment in London’s electricity infrastructure. Other major projects underway in the capital include London Power Tunnels 2 (LPT2) and the North London Reinforcement (NLR) scheme, reflecting the growing need for modern and resilient transmission infrastructure.
Extensive Network Reinforcement
The North West London Upgrade involves several interconnected elements across Bedfordshire, Hertfordshire and London.
At Sundon, National Grid will upgrade the existing substation to improve its ability to support the reinforced transmission network. Along the 35-kilometre Sundon–Elstree overhead line route, existing conductors will be replaced through a major reconductoring programme.
The works will upgrade more than 200 kilometres of overhead line infrastructure along the route, increasing its capacity and improving the overall performance of the transmission system.
At Elstree, the existing 400kV GIS substation will be extended, while the new Letchmore Heath GIS substation will be constructed next to it. These facilities will form an important part of the network required to accommodate rising demand in Hertfordshire and North West London.
Further upgrades will take place between Elstree and St John’s Wood. A new 400kV cable circuit will be installed inside the existing Elstree–St John’s Wood tunnel, alongside upgrades to the tunnel itself and its associated headhouses. The existing St John’s Wood substation will also undergo reinforcement.
Making Use of Existing Infrastructure
A key feature of the programme is the use of existing infrastructure wherever possible. The Elstree–St John’s Wood tunnel extends for more than 20 kilometres and already houses some of the longest alternating current (AC) transmission cables on the transmission network in England and Wales.
The tunnel was originally designed in the early 2000s with sufficient space to accommodate an additional cable circuit if future electricity demand required it. The NWLU will now make use of that planned capacity by installing a new circuit within the existing tunnel.
Alongside the tunnel works, approximately 60 kilometres of new cable infrastructure will be installed within the existing route. Using existing underground infrastructure can help reduce the need for entirely new transmission corridors while allowing National Grid to increase capacity in a highly developed part of the country.
The combination of overhead line reinforcement, new cable infrastructure and substation improvements is intended to provide a coordinated solution to the region’s future electricity requirements.
Major Delivery Partnerships
National Grid is working with a number of engineering and construction partners to deliver the complex programme.
Laing O’Rourke has been appointed to carry out substation works at Letchmore Heath, Elstree and St John’s Wood. HMJV will be responsible for cable installation and upgrades to the existing tunnel infrastructure.
Hyundai Electric will supply and install major electrical equipment, including transformers, while Siemens Energy will provide shunt reactors for the Elstree substation.
The involvement of multiple specialist contractors reflects the scale and technical complexity of the NWLU programme. Coordinating substation construction, high-voltage equipment installation, tunnel works and overhead line upgrades will be essential to delivering the project safely and efficiently.
Joe Senior, project director at National Grid, said the programme represents a nationally significant investment that will strengthen the electricity network while enabling new connections and supporting economic growth.
He highlighted the importance of bringing together substations, cables, tunnels and overhead line reinforcement within a single coordinated programme to provide the infrastructure required for future homes, businesses and digital industries.
HMJV project director Raj Kundan said the company was proud to continue supporting National Grid in the delivery of critical national energy infrastructure. He also emphasized the importance of collaboration between National Grid, delivery partners and the wider supply chain.
Peter Lyons, managing director of Laing O’Rourke’s Europe hub, said the project builds on the company’s existing relationship with National Grid. Laing O’Rourke is already involved in several major electricity infrastructure programmes, including The Great Grid Upgrade, Wimbledon Asset Replacement, and the Margam and Port Talbot substations.
The company plans to use digital tools and construction technologies to support safe and efficient project delivery.
Creating Benefits for Local Communities
Beyond strengthening electricity infrastructure, the NWLU is also expected to provide benefits for communities located near the project.
In accordance with government guidance, communities close to the new Letchmore Heath substation will be eligible for up to £530,000 in funding. The money can be used for projects designed to improve local social, economic and environmental wellbeing.
This community funding is intended to create long-term benefits alongside the infrastructure investment, potentially supporting initiatives that improve local facilities, enhance the environment or contribute to wider community development.
Preparing the Network for the Future
The launch of the North West London Upgrade comes as the UK electricity system undergoes a major transformation. Electrification of transport, heating and industry, together with the rapid expansion of digital infrastructure and data centres, is increasing pressure on transmission networks across the country.
Projects such as NWLU are therefore becoming increasingly important in ensuring that electricity networks can accommodate new demand while maintaining reliability and resilience.
By reinforcing the network between Sundon, Elstree and St John’s Wood, National Grid is creating additional transmission capacity across a strategically important part of the UK. The project will help unlock new electricity connections, support economic and digital development and strengthen supplies for existing customers.
The programme also demonstrates the importance of combining new infrastructure with upgrades to existing assets. By using established transmission routes and an existing tunnel alongside new substations and upgraded overhead lines, National Grid aims to expand network capability while making efficient use of existing infrastructure.
As electricity demand continues to grow, the North West London Upgrade is expected to become an important component of the region’s future energy infrastructure. Its combination of high-voltage network reinforcement, new cable capacity, substation development and community investment positions the programme as a major step toward creating a more resilient electricity system capable of supporting North West London’s long-term growth.
Source Link: https://www.nationalgrid.com/
