The high voltage electricity transmission network in England and Wales operates largely at 400 kV and 275 kV. It connects separately owned generators, interconnectors, large demand users fed directly from the transmission system and the lower voltage distribution networks. 

Most lines of pylons on the network carry two electrical circuits. The network is planned and operated under a set of standards designed to ensure there are no widespread electricity supply interruptions, even if two circuits are out of service.

For example, if one circuit is switched out for planned maintenance and another is impacted by a fault at the same time, the Security and Quality of Supply Standard is designed to ensure: 

• electricity system frequency is maintained within statutory limits 
• no part of the network is overloaded beyond its capability
• voltage performance stays within acceptable statutory limits 
• the system remains electrically stable. 

ESO oversees the standards that we maintain on the system; however, they are approved by a Security and Quality of Supply Standard panel and Ofgem.

With growing offshore wind and interconnectors, an anticipated tripling of wind generation connected across the Scottish networks by 2030 and Government’s increased ambition to connect 50 GW of offshore wind by 2030, north–south power flows are set to increase. National Grid ESO in the Electricity Ten Year Statement anticipates that the network between the North and the Midlands needs to be capable of transferring around 25.9 GW of electricity by 2033, compared to 11.6 GW that it can transfer today.

Where power flows from one part of the network to another exceed the capability of the network across what we call ‘transmission boundaries’, one of two things needs to happen. 

The System Operator might pay generators to reduce the energy they produce in one part of the country while paying others elsewhere to generate. These payments are called ‘constraint payments’. Balancing the network in this way can temporarily manage power flows where network capability is insufficient, but increases operation costs, as more expensive generation is brought on. This can be an economic way to manage the network up to a point, if constraint costs are not disproportionate. Where constraint costs are substantial, the network becomes uneconomic to operate. It then becomes necessary to invest in increasing network capability.

The existing network serving the South Humber Bank area is already exporting significant amounts of power, which contributes to the North to Midlands power flow challenge on the existing network. Elsewhere across most of the eastern half of Lincolnshire, where new sources of electricity are planned to come ashore, there is no existing electricity transmission infrastructure.

Peak demand for electricity in the region in 2022 was 785 MW according to results in the Future Energy Scenarios 2023 report by ESO for the Leading the Way scenario for North East Lincolnshire, East Lindsey District, Boston Borough, South Holland District and Fenland District Council areas. Towards the end of this decade, electricity demand in the region is forecast to be slightly lower than it is today, at around 764 MW in 2030, before starting to rise thereafter to 823 MW by 2032.

Table 1 Proposed new connections in the region

In addition, Table 2 lists several high-voltage direct current (HVDC) subsea links that are planned to come ashore and connect to substations in the region.

Table 2 Proposed HVDC subsea links

With no reinforcements, the network would not have the capacity needed to export all that electricity out of the area across both the B8 and B9 boundaries. We therefore need to reinforce our network::

• to maintain system compliance and prevent circuit overloads from happening; and

• to connect proposed new sources of electricity in locations where the electricity transmission network does not extend today.

Before building new lines, we look first at whether we can carry out works to our existing network to deliver more power carrying capability. Work to derive more capability out of the existing network across transmission boundary B8 is planned in the next decade, including: 

• reconductoring Keadby to Cottam (Keadby to Cottam reconductoring is referred to as KCRE in NOA and received a ‘proceed’ recommendation in NOA 2021/22 and NOA 2021/22 Refresh)
• thermally uprating Keadby to West Burton (Keadby to West Burton thermal uprating is referred to as KWHW in NOA and received a ‘proceed’ recommendation in NOA 2021/22 and NOA 2021/22 Refresh.)
• installing new power control devices along Keadby to West Burton (Reconductoring West Burton to Ratcliffe on Soar is referred to as WRRE in NOA and received a ‘proceed’ recommendation in NOA 2021/22 Refresh)
• uprating the existing line from 275 kV to 400 kV from Brinsworth to Chesterfield to High Marnham (Uprating Brinsworth to Chesterfield to High Marnham from 275 kV to 400 kV is referred to as EDEU in NOA and received a ‘proceed’ recommendation in NOA 2021/22 Refresh.)
• reconductoring West Burton to Ratcliffe-on-Soar (Reconductoring West Burton to Ratcliffe on Soar is referred to as WRRE in NOA and received a ‘proceed’ recommendation in NOA 2021/22 Refresh)

When replacing the wires (conductors) on overhead lines, it is sometimes possible to do that on existing pylons with new wires that can carry more power – and sometimes with wires that can be operated at a higher temperature allowing more power to be transported. That is what we are doing with the first two schemes. Power control devices are equipment that allow more power to be directed to flow along parts of the network that have some additional capacity.

While those works will increase the boundary transfer capability across boundary B8 to around 14 GW, they will not be sufficient to accommodate the north–south power flows that are expected on the network. Up to around 29 GW of boundary transfer capability is needed by 2033 across the B8 boundary to account for increasing offshore wind generation interconnectors.

Work to derive more capability out of the existing network across transmission boundary B9 is planned in the next decade, including: 

• reconductoring Enderby to Patford Bridge to East Claydon
• thermally uprating the Cottam to Market Harborough to Grendon circuit.

While those works will increase the boundary transfer capability across boundary B9 to around 15.6 GW, they will not be sufficient to accommodate the north–south power flows that are expected on the network. Around 22.4 GW of boundary transfer capability is needed by 2033 across the B9 boundary with increasing offshore wind and interconnectors.

Every year ESO looks at how much energy needs to be carried on the network in the future and where network capability needs to be improved to accommodate that.

1. That starts with the System Operator identifying a range of Future Energy Scenarios which are discussed with stakeholders and published each summer. Future Energy Scenarios represent different credible scenarios for how quickly we might make the transition to a cleaner, greener energy future as we strive towards net zero by 2050. 
2. The Future Energy Scenarios inform the analysis in the Electricity Ten Year Statement which is published each autumn, setting out ESO’s view of future transmission requirements and where the capability of the transmission network might need to be addressed over the next decade.
3. Transmission Owners, which for England and Wales is NGET, then respond with solutions to address the requirements identified in the Electricity Ten Year Statement. We work with energy consumers in mind, making sure we focus on transmission system proposals that offer the best value and can be delivered in an efficient and coordinated way. ESO assesses and publishes its recommendations as to which proposals should proceed in a Network Options Assessment (NOA) report each year. 

In summer 2022, a refreshed NOA was published alongside the System Operator’s Pathway to 2030 Holistic Network Design (HND), setting out a blueprint for the connection of the offshore wind needed to meet the Government’s 2030 targets.

In planning and operating the network, transmission licence holders – onshore and offshore – are required by their licence to comply with the National Electricity Transmission System Security and Quality of Supply Standards (NETS SQSS). These set out criteria and methodologies for planning and operating the transmission network in the UK – in essence, minimum requirements designed to ensure secure and stable electricity supplies.

The NOA 2021/22 Refresh was published in July 2022; it updated an annual report from ESO which outlines its recommendations for which network reinforcement projects need to be taken forward and when. The report also recommends the most economically suitable investment strategy for these reinforcements and outlines the pathway to 2030 and beyond. 

This project, along with others, is a priority because the Midlands, South and East of England – which covers areas spanning from the Humber in the North to East Anglia and the Thames Estuary in the south – have been identified as areas in need of network reinforcement to enable the connection of more offshore wind on the East Coast. 

The System Operator has identified this and other reinforcements in NOA as ‘HND essential’ to deliver the Pathway to 2030 Holistic Network Design – connecting offshore wind needed to meet the Government’s offshore target for 2030. The System Operator also advises in NOA that the reinforcement needs to be accelerated to help meet Government’s 2030 offshore wind target. 

Grimsby to Walpole therefore forms an important part of our plans for this region – helping increase power flows from the North to the Midlands and facilitating the connection of solar and offshore wind interconnectors.

Our approach to developing new electricity transmission proposals includes the following key stages:

The Strategic Proposal stage involves identifying potential options that will meet the need to reinforce the network that has been identified by the System Operator and provide physical connection points for customers in and around the local area. Thereafter, at the Options Identification and Selection stage, we look at potential corridors where the proposed new infrastructure might be most appropriately located. This is the stage that we are currently at. 

We have identified a strategic option and an emerging preferred corridor that meets the network reinforcement requirement. We are sharing information about those early so that we can consider everyone’s feedback as we further develop our proposals. You can read more about how we develop our proposals at the project development and delivery stage in

Our Approach to Consenting. 

The sections that follow give an overview of the need for network reinforcement in the region; the work we have undertaken to identify a strategic option; our emerging preferred corridor; information about this first stage of consultation; how you can give us your feedback; and next steps.