Our proposals

Our network studies show that the reinforcement between Bramford and Twinstead needs to be in place by 2028.

In picking up the proposals again, we have carried out a thorough re-appraisal of the scope of the works and our decisions to date.

Through that review we have been able to reach a fully informed and up to date position on the project. We are confident that our 2013 proposals remain largely appropriate, but the review has identified some areas for further consideration.

Further details of our review and the emerging proposals are set out in the Project Development Options Report.

What does Bramford to Twinstead include?

The proposals include the following components, which we would like your thoughts and views on during the consultation:

  • 1constructing approximately 27 km 400 kV electricity transmission connection between Bramford Substation in Suffolk to Twinstead Tee in Essex, comprising 19 km of overhead line and 8km of underground cable (4km through the Dedham Vale AONB and 4 km in the Stour Valley)
  • 2constructing four cable sealing ends at the points where overhead lines meet underground cables
  • 3removing 25km of existing 132 kV overhead line operated by UK Power Networks, between Burstall Bridge (approximately 2.5 km south of Bramford Substation) and the diamond crossing.
  • 4constructing a new substation at Butlers Wood to enable the removal of UK Power Network’s 132 kV overhead line. A new substation is needed to maintain the electricity supply to local homes and businesses
  • 5removing around 1 km of the existing Bramford to Braintree to Rayleigh 400 kV overhead line south of Twinstead Tee
  • 6constructing an alternative alignment for the existing 400 kV line around Hintlesham Woods to allow the new line to adopt the current route through the woods.


You can use our interactive map to view the route.

You can also click on specific sections which will give you more detailed information about the plans.

View map

Project costs

As part of our review, we have also reconsidered the costs of building the reinforcement.

Market and material costs will change before we reach construction, but based on current information and designs, in today’s (or equivalent) prices, the total estimated capital cost of the proposed scheme is approximately £363m. Of that, overhead line costs account for approximately £78m. Underground cables, including cable sealing ends at £5m each, account for approximately £245m. Substation works are £40m of which £27m is the new grid supply point at Butlers Wood.

The cost of putting high voltage cables underground is substantially higher than putting them overhead, and those extra costs ultimately fall on everyone’s electricity bills. The duties placed on us by the Electricity Act 1989 require a balance to be struck between the visual impact on the landscape and the cost to electricity bill-payers, so we must consider every case for installing cables underground on its merits.

National Policy Statement EN5 explains that Government expects the need for new electricity lines to be often fulfilled through the development of overhead lines. Government does not see the development of overhead lines as inconsistent with our environmental duties, but Government recognises there may be instances where overhead lines may not be appropriate.

Cases for installing cables underground could include locations where it would be physically difficult to build an overhead line (such as in urban areas), wide river or estuary crossings, and highly valued landscapes. These may include National Parks and Areas of Outstanding Natural Beauty but could also include particularly sensitive landscapes, areas with iconic views or other places where the potential impact of a new electricity connection could only be mitigated by putting it underground.
The additional cost of undergrounding in this instance, for example, at the Stour Valley compared to using overhead lines, is £118m. The additional cost of undergrounding the Dedham Vale compared to using overhead lines is £107m. To use overhead lines throughout the route would cost £142m, compared to the cost of a fully undergrounded scheme, which would cost £694m.

The BEIS review of offshore coordination

The Business Energy and Industrial Strategy (BEIS) department’s Offshore Transmission Network Review is currently looking at how the offshore electricity transmission network can be delivered in a more coordinated way to deliver net zero emissions by 2050, and we fully support that work. We will work closely with Government, stakeholders and coastal communities to ensure we play our part to deliver the infrastructure needed to achieve net zero in a way that reduces impacts on communities.

In meeting that challenge there are two key considerations. The first is the way in which we best connect and coordinate the growth of offshore wind farms and interconnectors to the electricity transmission network along the immediate coastline. The second is the network reinforcements required further inland to accommodate the increased demand on the network and to ensure we can effectively transport the power to where it is needed across Great Britain.

That offshore coordination work by Government is ongoing. As explained in the Energy White Paper, Government will be looking to redesign the current regime to bring more extensive coordination and mitigate environmental, social and economic costs for the 2030s and beyond. While developers will be encouraged, where early opportunities for coordination exist, to consider becoming pathfinder projects, National Grid ESO explains in the latest Network Options Assessment, that onshore reinforcement is still needed. The System Operator’s analysis found that the viable offshore options, in the scenario where 40 GW of offshore wind is achieved by 2030, do not displace any of the onshore reinforcement requirements that have been identified.

Notwithstanding how offshore coordination is developed, major onshore development and electricity network reinforcement will therefore still be necessary. To put this into perspective, successfully delivering the Government’s 40 GW of offshore wind ambition will require around 500km of onshore and around 400km of offshore electricity transmission network being consented and delivered within this decade across the east side of the country.

The network reinforcement between Bramford and Twinstead Tee is an integral part of that and is considered ‘critical’ for 2028 by National Grid ESO in all of the Future Energy Scenarios.