Strategic Wider Works

Delivery of large onshore electricity transmission projects

Our role is to ensure that new large onshore electricity transmission projects that are needed are delivered efficiently. We do this through:

  • regulating the delivery of these projects by incumbent Transmission Owners (TOs), via our Strategic Wider Works (SWW) mechanism; or
  • introducing competition into the delivery of these projects.

In January 2018 we published an update to our plans to introduce competition into onshore electricity transmission, available here.

SWW Mechanism

As part of the RIIO-T1 price control we put in place a mechanism to allow TOs to bring forward large investment projects where funding had not been awarded as part of the price control settlement.

SWW allows us to consider the need and funding for these projects during the price control period, so that delivery of these outputs can be brought forward in a timely manner.

The TOs have identified in their business plans a number of projects that they consider are suitable for future consideration under the SWW arrangements. Other projects which meet the eligibility criteria set as part of the price control, may also be brought forward.

Onshore competition

During RIIO-T1 we will also look at whether it is appropriate to introduce, or replicate the outcomes of, competition in the delivery of SWW projects.

Approved SWW projects

Since April 2013 we have approved funding for three SWW projects:

Current and future potential SWW projects

The annual Network Options Assessment (NOA) report, most recently published by the GB System Operator (SO) in January 2018, identified several network reinforcement options as potential SWW projects in future. The potential SWW projects listed in the table below are existing SWW projects or those with a ‘proceed’ recommendation in this year’s NOA. We have also included in the table existing SWW projects proposed by TOs that have not yet reached the stage of being approved for funding.

In the January 2018 NOA the SO also provided its assessment of current and potential future SWW projects against our criteria for competition - we have added the outcomes of that analysis to the table below.

Project name


Earliest in service date

Ofgem status NOA Onshore competition analysis

Western Isles link

A subsea HVDC link between the Isle of Lewis and Beauly, comprising 80km of land cable and 76km of subsea cable.


Possible future submission Suitable

Orkney Islands link

An AC subsea cable rated at around 200MW between Orkney and northern Scotland.


Possible future submission Suitable

Shetland Islands link

A subsea HVDC Link between Kergord on Shetland and Caithness, or alternatively landing in Morayshire.


Possible future submission Suitable

Eastern Network Reinforcement

Exact design still to be confirmed. Likely to include a subsea HVDC cable between Hawthorn Pit and either Torness or Peterhead, and an onshore 400kV reinforcement.

2023 - 2028

Possible future submission Suitable

Hinkley - Seabank

A new 400kV double circuit overhead line between Hinkley Point and Seabank.


Final Needs Case approved in January 2018 -

North West Coast Connections

A new 400kV double circuit connection for a proposed new nuclear power plant in Moorside.


Paused -

South East Network Reinforcement

A new 400kV transmission route between south London and the south coast

2027 Possible future submission Suitable

Need help?

This page sets out information on the policy and processes around delivery of large onshore electricity transmission projects. If you're looking for information on other aspects of onshore electricity transmission, please refer to the transmission networks page.

If you can’t find the information you’re looking for, email us.


Publications and updates

  • Published: 19th Dec 2013
  • Guidance
  • 1 Associated documents
This page provides a brief overview of the SWW arrangements for our wider stakeholders.

  • Published: 21st Oct 2013
  • Guidance
  • 2 Associated documents
This document provides information for stakeholders on the Strategic Wider Works arrangements that were introduced as part of RIIO-T1.