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Supercharging the supergrid

It feels inevitable that any discussion about energy in the UK – and even around the world – comes back to a discussion around the grid. National Grid has raised the possibility of increasing the capacity of existing links, in order to get ahead of the problem, rather than continuing to react to events.

John Pettigrew, CEO of the National Grid, set out this potential new way forwards at the Aurora Spring Forum on Tuesday. The executive called for a move to a “super-supergrid” as one option to tackle grid congestion.

He started by noting the transformation of the grid starting in the 1950s. At that point, the grid was at capacity with the country divided into seven distinct networks.

Demand was rising, while new sources of geographically constrained supply – in this instance coal in the East Midlands and Yorkshire – was emerging.

National Grid's John Pettigrew
National Grid’s John Pettigrew

The engineers at the time opted to design a supergrid, building out infrastructure that could get ahead of the then squeeze. Expanding infrastructure like this paved the way to allow future upgrades to be brought on more easily. The plan was delivered and electricity enabled a “whole new world of opportunity”.

Pettigrew said the country had reached a similar point now. The country needs to take a similarly radical step in order to make the grid future ready.

“Do we need to take a collective step back, and consider whether there are alternative long-term approaches to build a grid that is fit not just for the next 20 years, but for the next 60,” he said.


One way to tackle this would be for National Grid to build an “ultra-high voltage onshore transmission network” over the existing supergrid. Existing onshore high voltage lines could double to 800 kV, he said, creating a “super-supergrid”.

Superimposing this new grid capacity over the existing network would be backed up with “strategically located ultra high capacity substations, supporting the connection of big energy sources to big demand centres via the new network”.

RenewableUK director of future electricity systems Barnaby Wharton welcomed plans to expand grid capacity. “Everyone agrees we have not invested enough in the grid to date. Now we have to play catch up.”

Focusing on the expansion of capacity on the existing network, Wharton said there were “already a lot of lines on the map. We don’t necessarily need to draw more lines on – but how thick are those lines? It sounds like a sensible idea.”

Building new transmission lines can face challenges from community and landowners. “If it’s just replacing one set of transmission lines with another, that’s a whole different discussion,” the official said.

The recently published Beyond 2030 report also noted potential around “utilising existing route corridors and where possible existing infrastructure”.

Big vision shift

Current thinking on the grid is “incremental, tactical and reactive”, Pettigrew told attendees in Oxford. A bold step into a higher capacity grid would be strategic and proactive.

Focusing on major capacity hubs would provide a way to focus investment on key areas, moving away from individual connection points across the country. The new substations would also have spare connection points, allowing new customers to link up faster and more flexibly.

National Grid is working on grid expansion beyond Pettigrew’s super-supergrid plan. The Great Grid Upgrade will see 17 infrastructure projects built out with the aim of connecting new sources of renewable power to the system.

For instance, earlier this month, the government approved the Yorkshire GREEN project. This aims to increase the grid capacity from the north of England to the south.

RenewableUK’s Wharton said current plans failed to consider future possibilities. “We’ve been risk averse and focused on minimising the short-term costs for consumers. That’s a key point for regulators, but as a result we’ve lost long-term value.”

The ambitious super-supergrid plan does raise some “stranded asset” risks. “However, we know we’re going to need more electricity and we need to move it around the country more effectively. Let’s have some bold ambition. It’s a bit of a risk – but it’s a pretty good bet.”

Deepening the grid in the way set out would enable more offshore wind, more onshore wind, more batteries and make the system overall more flexible, he said.

“We’ve seen constraint costs jump hugely last year because we’re paying more for gas. This could help insulate us from external price shocks. All these things should be seen as a whole.”

Finding a balance

Other countries have rolled out 800 kV lines in order to balance their grids. China has been a major proponent of these links, while Brazil and India have also built some high capacity assets.

The UK has made slower progress. However, there have been some plans for offshore connections. Prysmian, for instance, announced it had won work on the Eastern Green Link 1 project in November 2023. This will run from East Lothian, in Scotland, to County Durham in England.

Prysmian reported this would be the first contracted cable system in the UK to use 525 kV HVDC technology. The link will provide transmission capacity of 2 GW.

This link highlights a way to tackle the grid problems with the B6 bottleneck, which roughly runs along the border between Scotland and England.

The super-supergrid would help smooth out the differences between the zones, Wharton said. “Locational pricing is trying to tackle the lack of grid. If we’re going to be building more renewables in the north of Scotland, we need to build that grid anyway. Locational pricing is an economic sticking plaster on an infrastructure issue.”

Pettigrew’s vision of a super-supergrid is radical and ambitious – and crucially shows a way to get ahead of the cycle of capacity crunches that the UK is in. Other countries have built out long-distance high-voltage capacity to deliver power to where it has needed. Britain has done it before. There seems to be little reason not to do it again.

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