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A Congested Substation

The very first offshore wind turbines built in the UK were in December 2000, off the coast of Northumberland. They were built as a demonstration with two 2MW turbines, and at the time, they were the largest offshore wind installation in the world.

As time went on the size of the turbines and developments increased. In 2012 the first 500MW offshore wind farm was installed. This is the Greater Gabbard windfarm and sits off the coast of East Anglia. By the end of 2012, 56% of the worlds capacity of offshore wind energy was in the UK.

In 2019 the first offshore wind farm exceeding 1GW began operation, and several of the new East Anglia offshore windfarms were announced to be developed without government subsidies.

Overloading the System?

Now whilst all this offshore wind generation might be amazing, it isn’t so great having it stuck out at sea. At some point it needs to come onshore and be transmitted across the UK. And this presents problems. Specifically congestion problems, and is outlined in this letter from the Offshore Wind Industry Council (OWIC) which states “the UK is already seeing examples of physical and grid congestion.”

Physical congestion refers to space for the cables and overhead power lines to actually physically be, as well as the substations that handle the energy. You can’t put two cables in the same place. At best they can be next to each other. If too many cables go in, space runs out for more. And grid congestion refers to the energy capacity of those cables and substations. For example, even if you could get your elbow to your ear it still won’t fit inside it.

East Anglia is having a particularly difficult time with this congestion, and it was illustrated very well on page 7 of this report by OWIC in 2019. To note, blue squares represent existing substations. Black items represent existing power lines and power generation from offshore wind, nuclear, and interconnectors (power lines from Europe). Red represents anything planned but not yet operational. You will notice the importance of Bramford substation in this map as a significant amount of renewable energy is planned to come through it. And as you can see clearly in the middle, there is 22GW of generation to come in, but only 15GW of transmission lines to get it to the rest of the country.

At this point we’d like to explain that there are two levels in the electricity network. There is the high powered national network called the “transmission network” which is managed by National Grid at voltages of 275kV and 400kV. And there is the lower powered local network who distribute the power to homes and businesses in the “distribution network” which is operated by Distribution Network Operators (DNO) at voltages of 132kV and below, right down to the 240V we use in our homes. There are 14 DNO’s in the UK, and the one local to us is called UK Power Networks.

Physical Congestion

One of the concerns of the OWIC was about physical congestion. If you’ve seen the area around Bramford substation lately you’ll have noticed the overhead lines. But what you won’t notice is the amount of underground cables there are too. Most recently the underground cable for the EA1 Offshore Windfarm was laid and connected to the substation. The area around Bramford, both above and underground, is becoming physically congested. Covering what is left with solar panels restricts the physical space even more.

Moving away from the idea of using this land for growing British food for a moment, the UK Government states in the National Planning Policy Framework (2019) paragraph 117 “Planning policies and decisions should promote an effective use of land…”

Filling the land around Bramford substation with solar panels of an export capacity up 49.9MW versus using the land to lay cables supplying electricity with up to 9,600MW is a gross waste of physical land space. Not to mention that if the cables are laid underground it means that British food can still be grown on top of it making it an even more effective use of the land.

Furthermore, paragraph 11 of the NPPF states “Plans and decisions should apply a presumption in favour of sustainable development. For decision-taking this means: d) where there are no relevant development plan policies, or the policies which are most important for determining the application are out-of-date, granting permission unless: i. the application of policies in this Framework that protect areas or assets of particular importance provides a clear reason for refusing the development proposed.”

Bramford substation is a nationally important asset for the UK’s renewable energy future in our electricity grid and keeping the area around it free for (ideally underground) cables that bring energy in from the offshore windfarms and then transmit it out across to the rest of the UK, and for grid stability improvements like the Pathfinder initiative being rolled out in Scotland (needed because of the huge contribution of wind power in that area needing to be enhanced to ensure it is compatible with our domestic use and stopping ‘flicker’ on our TV screens) is a clear reason for refusing the solar farm.

Grid Congestion

The second concern of the OWIC was that of grid congestion. Once you’ve got a cable physically in place, that cable still has a limit on what it can carry. Think of it like trying to move a 3 piece suite. There’s no point hiring a Mini to do that job, you’d need a Ford Transit.

At this point it is important to explain how Enso Energy and EDF Renewables plan to connect their solar farms into this system. Both developments are due to connect to something called a “tertiary connection”. This is a type of connection available within some substations. At Bramford substation there are 5 of these. EDF Renewables (via Pivoted Power) and Enso Energy have two of these. More on the other three in a moment.

A tertiary connection connects directly into the transmission network with National Grid. This is the high powered network, and the same one that all the Offshore Wind and Nuclear Stations connect into. Not the local distribution network like the solar panels on a home or warehouse rooftop would.

In 2013 the UK Government published the UK Solar PV Strategy. It’s 4th principle states “Support for solar PV should assess and respond to the impacts of deployment on: grid systems balancing; grid connectivity; and financial incentives – ensuring that we address the challenges of deploying high volumes of solar PV.” Enso Energy even refer to this policy on page 17 of document R003 of their planning application.

We covered above that East Anglia has a capacity issue. It has 22GW of energy coming in, and only 15GW of equipment to get it to the rest of the UK. It seems that with Enso Energy and EDF Renewables connecting into an already overloaded grid that they are not following this planning principle set out by the UK Government. They are adding to the problem.

In addition to this the UK Government are calling for “smart distribution of solar PV”. Distributed or embedded solar is mostly that which you would find on rooftops, car parks, and most brownfield sites connected to the distribution system. It is also produced at a lower voltage level which means it avoids the waste loss of transforming the energy up to high voltage and then back down to low voltage. Although some greenfield can connect into the distribution network too, most suitable sites for embedded generation are on brownfield areas, using existing infrastructure. Essentially smart distribution connects into the distribution network where it is generated and used locally. By doing this it reduces the demand on the high powered transmission network which transmits the energy over large distances. Energy embedded in the distribution network also means less energy is wasted, because the further energy has to travel the more that gets lost along the way due to electrical resistance in the metal. Think of it like carrying a bucket of water with a small hole in it. The further you carry the water the more you’ll lose along the way.

In December 2020 the UK Government issued their “Energy White Paper” where they lay out their roadmap for a smarter, cleaner energy system. This started several years ago with the introduction of smart meters, and more recently the growing adoption of smart appliances and technologies. And as more electric vehicles come onto the system integrating them into how the system operates demands a smart distribution system. Page 25 of the white paper calls for a smart local energy system, and starting on page 70 it explains the need for this to be decentralised (i.e. distributed/embedded) by 2050 to meet our climate change goals is imperative. Solar is an ideal embedded generation solution for the distribution network, roof top mounted, in the heart of the network where it is going to be used.

By connecting solar to the transmission network, as Enso Energy and EDF Renewables intend to do, goes completely against this smart movement and worsens the imbalance by requiring both physical and grid capacity at our substations for the solar AND for its replacement on dark nights and cloudy days.


In summary let’s circle back to those three remaining tertiary connections at Bramford substation. In an email conversation with National Grid in November 2020 they told CARE Suffolk that they “took the decision to remove the remaining tertiaries, until detailed engineering assessments have been completed to understand the impacts of additional generation on the network and how this interacts with the vast amount of projects already contracted to connect” and that “there is currently substantial Transmission Reinforcements Works planned to help facilitate the connection of large scale Offshore & Nuclear generation. It is likely that any additional direct connections at Bramford will sit behind these works and connecting parties.”

It seems National Grid have not only removed the uncontracted tertiary connections because there isn’t space to accommodate the potential generation in an already overloaded system, but also that these tertiary connections will be unavailable permanently because they don’t need anymore generation connecting into Bramford. Enso Energy and EDF Renewables are clearly adding to the congestion problem and not following Government planning policy in choosing to connect in this location.

4 thoughts on “A Congested Substation”

  1. Thank you for an insightful article that raises issues of concern for us at the Twinstead end of the Bramford to Twinstead Connection Project (B2T). If further connections are choked off by congestions at Bramford and Twinstead gets a substation as part of the B2T project, will we become a target for solar farm developers?

    1. We are unable to say for certain. What we do know is that large scale developers have been targeting a type of connection called a “tertiary connection”, which is found at substations. This is the third winding on high voltage transformers. If National Grid were to make these connections available for commercial connection, then the chances are quite likely that landowners in your area would be targeted by them.

  2. Pingback: Greybarn Solar Farm – CARE Suffolk

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