Overview
Pelham Substation is the northern point of the North London Reinforcement (NLR) project. It is a key part of the wider programme to upgrade the electricity network and strengthen power supplies into London.
The equipment at Pelham is nearing the end of its operational life and needs upgrading. This will increase how much electricity the substation can carry. We will replace transformers and other equipment with higher-capacity units so the system can run at a higher voltage.
By upgrading the site, we can strengthen the wider network so it can take more energy from renewable sources. These works also ensure the network remains safe, reliable and able to meet growing demand from homes and businesses.
What is taking place?
We will be extending the substation and installing two new quad boosters. Quad boosters are specialised pieces of equipment that help control the flow of electricity. They will increase how much electricity the substation can transmit and help to keep the system balanced.
We are working with UK Power Networks (UKPN) to reroute a short section of overhead line and underground some cables as part of these works, which will see a total of 11 pylons removed around the substation.
To facilitate the increased capacity at the substation, we will also be updating the existing overhead line route between Pelham and Waltham Cross with higher voltage cables.
Construction activity
The main construction works have now started at Pelham. This includes the construction of a haul road around the substation, and the removal of an existing transformer.
To support the timely delivery of the project, construction activities will take place between 7am to 5pm, Monday to Friday. Some work may take place at weekends, subject to project requirements.
We anticipate that all works will end in 2030 and activity is expected to take place in phases.
Keeping communities informed
We aim to minimise the impact of our project as much as possible and to keep people informed about the work we’re doing at Pelham.
We have held Community Liaison Group (CLG) meetings with local stakeholders to understand where we can work with local residents and minimise disruption. Our first meeting was on Wednesday 15 April 2026. You can view the slide deck from the meeting here.
Register your details with us here to receive information as it becomes available. You can also follow our WhatsApp channel for real-time updates on our activity. Read our Frequently Asked Questions document, including the QR code you can scan to join.
Community fund
We are developing a community fund to recognise and reward the communities near the project. Before it is launched, we are working with local groups, community organisations and key stakeholders to help us understand local needs, priorities and long-term aspirations.
Our first workshop for Pelham was held on 6 May 2026. Thank you to all who attended. You can view the presentation slides we used here.
Frequently Asked Questions
Works at Pelham
Our timetable at Pelham is still being developed and may change. This is because we need to fit works around planned outage windows, key equipment deliveries and activity across the wider programme. We also need to coordinate timing with other sites and construction phases so the overall scheme can be delivered safely and effectively.
Based on the current developing programme, the expected sequence of works at Pelham is as follows:
- Haul road construction: April–May 2026
- Existing transformer demolition: April 2026 – July 2026
- Quad booster construction works: April 2026 – December 2026
- Vegetation clearance: October – December 2026
- Quad booster delivery: January/February 2027 (subject to confirmation)
The extension will be along the eastern edge of the substation, at a total footprint of 40 x 60 metres. It will be parallel to the footpath that runs alongside the substation. The additional space will house a new quad booster and cable sealing end compound. The cable sealing end is a covering that will connect overhead lines to underground cables.
The quad boosters, whilst larger in size than Supergrid Transformers (SGTs), are the same height as the SGTs in the substation at present (between 5 and 8 metres). We will be installing a wall around the new quad boosters.
To facilitate the uprating, some cables will need to be rerouted underground. As a result, four National Grid owned pylons and seven UKPN owned pylons will be removed. We are not removing any pylons for the overhead line works outside of the substation footprint. We are instead replacing the conductors with higher voltage lines.
The NLR project has no relation to customer connections. The need to upgrade the substation sits outside of new developments, of which National Grid has no deciding powers. It is true that reinforcement projects do generate interest from customers, however, NLR has not received any notifications from National Grid’s customer connections team that this is the case at Pelham.
We are carrying out detailed noise assessments to understand how construction may affect the area. There may be times when construction noise levels are higher than usual, however, we do not expect this increase to be significant. We will plan any noisier work carefully to keep both the duration and impact as low as possible.
All work will take place during standard construction hours (Monday to Friday, 7am to 5pm). If we need to work outside these hours, we will seek permission in advance. We will also make sure this is properly managed and clearly communicated.
Traffic management
We do not anticipate needing to implement any road closures during the majority of construction works at Pelham Substation. The works are being carried out within the existing substation site and on adjacent land currently owned by National Grid, meaning no external construction activity on the surrounding road network is required.
The only exception is during the delivery of the quad booster. This is a very large piece of equipment that must be transported under escort through the county. For safety reasons, this delivery will require short-term, temporary road closures while it is taking place. These closures will be carefully planned, managed and coordinated with the local highway authority. They will be kept to the shortest and safest duration possible.
We will provide advance notice of any temporary road restrictions associated with the quad booster delivery, including clear information on timings and alternative routes, so the community can plan accordingly.
Public Rights of Way will be maintained, and footpaths will remain open where possible. For our overhead line reconductoring works, we have closed a bridleway just south of the substation site at East End until 25 April. We will be closing the area again from 29 July to 11 August. For more information on any closures, please visit our traffic management page here.
To ensure safety, we will also implement a small local diversion at the substation access gate. This is to protect pedestrians from construction vehicles entering and exiting the site and will be clearly signed and managed.
The final routes are still being developed and have not yet been confirmed. This work involves detailed planning and ongoing discussions with the local highways authority to ensure routes are safe and suitable.
When identifying routes, we consider factors such as road safety, local access, and minimising disruption to residents where possible. The highways authority plays a key role in reviewing and approving these plans.
All contractors working on the project will be required to follow the agreed routes. These routes will form part of the project’s traffic management plans, and drivers will be clearly briefed on them before carrying out any journeys.
If you’re concerned about HGV movements, please contact our community relations team.
We are working closely with Hertfordshire County Council Highways to plan our vehicle movements and traffic measures. The highways authority oversees and coordinates activity across different projects in the area. This helps manage the overall impact on the road network and ensures that safety is maintained. While each project has its own requirements and timelines, we will continue to work through the appropriate channels to align plans where possible.
Environment
We are committed to delivering environmental improvements alongside our work at Pelham Substation. This includes plans for around 1.1 hectares of new planting to help enhance local habitats and support biodiversity.
We are also looking at opportunities to improve the existing ponds on site to provide additional habitat for wildlife.
Where possible, the design for the substation expansion was adjusted to avoid removing trees. However, it was necessary to remove a small number of trees to allow for the construction of the access road, and to ensure that emergency vehicles can access the site.
Before any trees were removed, ecologists checked for nesting birds and bats. No protected species were found. We continue to follow specialist ecological advice to protect remaining trees. This includes protecting tree roots, avoiding damage to habitats, and keeping tree protection measures in place throughout the works.
Safety
Security measures will be in place to help keep the site safe and secure. This includes security staff on site overnight when the site is not in active use. Additional measures may also be used where needed, such as secure fencing, lighting and monitoring systems. These are designed to protect the site, equipment and the surrounding area.
Fire safety is built into how substations are designed and operated, and this follows established practice used across the country and industry. The site has its own fire prevention and response measures, including specialist equipment and trained personnel to manage incidents quickly and safely. We will coordinate with emergency services where appropriate. These arrangements are standard for this type of infrastructure and are designed to ensure the site can be managed safely at all times.
Contact us
If you would like any further information or to speak to a member of the community relations team about the works, please use the contact form on our website or via the contact details below.
Email: [email protected]
Phone: 0800 538 5398