The way we generate electricity in the UK is changing rapidly, and we are transitioning to cheaper, cleaner, and more secure forms of energy like new offshore windfarms. This means we need to make changes to the network of pylons, cables and substations that transport electricity around the country, so that everyone has access to the clean electricity from these new renewable sources. 

In England and Wales, the electricity transmission network operates at high voltage – 400,000 volts (400 kV) or 275,000 volts (275 kV) - and is owned and maintained by National Grid Electricity Transmission.  

The electricity transmission network transports electricity in bulk around the country, from wind farms, power stations and other sources of generation, or from interconnectors that are connected to the network, and takes it on to the regional distribution companies or large electricity users. 

Below you can find more information about our proposals for these works. 

Norwich Main substation extension

Our existing substation at Norwich Main has been in service for around 50 years. And the time has come when we need to extend the site to enable new sources of electricity generation to connect into the grid, including the Hornsea Project Three offshore wind farm, the Equinor Sheringham Shoal and Dudgeon wind farm extensions.  

Map showing proposed works.
Map showing proposed works. View larger image.
Indicative visualisation of the existing substation (right) and proposed extension (left)
Indicative visualisation of the existing substation (right) and proposed extension (left). View larger image.
Close up indicative visualisation of the existing substation (right) and proposed extension (left). View larger image

The extension to the west will require us to submit a planning application to South Norfolk Council for approval. The eastern extension will be built under Permitted Development rights. 

Our Norwich Main substation has been in service for approximately 50 years, and as demand on the electricity network increases, we need to extend the substation to increase capacity. 

The Government has set a commitment to reach net zero greenhouse gas emissions by 2050 and has an ambition to connect 50 GW of offshore wind by 2030 – enough to power every home in the country.  

Public Consultation 

Our public consultation closed on 8 December 2023. We are now taking the time to review the feedback received before submitting our planning application to South Norfolk Council. 

We will update these pages when we have more information to share. 

If you would like to contact us further, you can by emailing [email protected] or calling 0800 0463 857   

Find out more 

You can view all of our consultation documents and materials below.   

Norwich Main substation extension – Leaflet 

Norwich Main substation extension – Exhibition banners 

Norwich Main substation extension – Feedback form 


Where is it substation located?

Norwich Main substation is located approximately 3 miles south of the city of Norwich, to the west of the A140 and south of the A47. The village of Dunston is to the west, and Swardeston to the east.  

Who is paying for Norwich Main Substation extension?

National Grid pays up front the many millions of pounds to costs to build a substation extension. The cost is then gradually passed to customers through their electricity bills over the next 40 years or so.  

The funding for these up-front costs  comes from National Grid’s shareholders and the institutions that lend us money. Across all our investments in our vital infrastructure, this amounts to many billions of pounds. They invest in us because they expect that we will make a sufficient profit to provide an appropriate return on their investment and eventually pay them back.  

This brings a major benefit to electricity bill payers as it allows the recovery of the cost of our investment to be spread out over many years, rather than having a spike in electricity bills when we build a large new transmission connection.     

Who will decide whether the Norwich Main Substation extension goes ahead?

National Grid will be submitting a Town and Country Planning Act (TCPA) planning application for the substation extension to South Norfolk Council, which will make a decision on the plans.

What interaction does the Norwich Main substation extension have with Norwich to Tilbury?

The extension of the substation is separate to our proposals for the Norwich to Tilbury project, which is proposed to connect into Norwich Main. It is primarily needed to connect the offshore wind farms listed above. However, it would also facilitate the connection of Norwich to Tilbury should that project be consented. 

How much land is needed for the substation extension?

We need approximately 5 hectares of land for the extension. 

Will the extension be taller than the existing substation?

The height of the extension and equipment will be similar to what is already there. 

Will any new overhead line/pylons be required?

No additional overhead lines or pylons will be required as part of the project. Three existing 132 kV pylons located to the south of the substation will be removed and replaced with a short section of underground cable to enable the extension. 

Will the extension increase the levels of electromagnetic fields (EMFs) at Norwich Main Substation?

Most equipment contained within substations produce very localised EMFs which reduce extremely quickly with distance, so at the perimeter fence the levels are low. In practical terms, this means that even substations operating at the highest operating voltages and currents are not capable of producing EMFs which exceed the public exposure limits outside the perimeter because of their design. The EMFs from substations themselves typically reduce to a background level a few meters from the perimeter fence, with exposures mainly from the cables and overhead lines entering and exiting the substation. 

Which projects are connecting into Norwich Main?

The Hornsea 3 offshore wind farm, and the Equinor Sheringham Shoal and Dudgeon wind farm extensions are contracted to connect into the new extension. Other customers are also planned to connect into the extension. The developers of these projects will provide more information on their proposals separately once their plans are more developed. 

Would Norwich Main Substation extension still be needed if the Norwich to Tilbury proposals went offshore?

Yes, the primary driver for the substation extension is to facilitate the connection of the Hornsea 3 offshore wind farm, Sheringham Shoal and Dudgeon wind farm extensions.

If the Norwich to Tilbury proposals went offshore, could the wind farms connect into that project rather than at Norwich Main?

No, these projects are too far advanced. Hornsea 3 offshore wind farm was granted consent in December 2020 and is under construction, and the Sheringham Shoal and Dudgeon wind farm extensions have been submitted to the Planning Inspectorate and have recently finished their Examination by the Planning Inspectorate.

When will construction start?

If approval is granted by South Norfolk Council, construction is expected to begin in Summer 2024. 

How long with Norwich Main Substation extension take to build?

Construction would be expected to take approximately 26 months. 

How will construction traffic access the site during construction?

Construction traffic would use the existing site access from Mangreen. Within the site, a new temporary access road will be built, in addition to the existing road. The majority of this temporary new road would be constructed as part of an unrelated Grid Park upgrade, which is being carried out under Permitted Development rights. The short remaining section would be built as part of any planning approval for the substation extension. 

Will the extension to the substation result in more operational traffic once it is built?

No, operational traffic will return to low levels once construction is completed. 

Female LPT worker

Contact Us

Please get in touch if you have any questions or comments on the Norwich Main Substation extension proposals.

Phone number: 0800 0463 857


Email: [email protected]