Yaxley Synchronous Condenser

Welcome to the information page for our synchronous condenser project, located in Yaxley, Suffolk.

In February 2023 Conrad Energy were granted planning approval to build and operate the Yaxley synchronous condenser project. This followed the contract award by National Grid Electricity System Operator (ESO) in November 2022, through the Stability Pathfinder Phase 3 tender process, to provide stability service technology across the UK.

Following the approval for the synchronous condenser project in February 2023 (planning application is available here), Conrad Energy made a further application available here to make a minor amendment to the layout and configuration of the development, known as a section 73 application under the Town and Country Planning Act, which was granted approval in June 2023.

View the full project brochure for the Yaxley synchronous condenser here.

The project is located at The Leys and Ivy Farm, Mellis Road, Yaxley, adjacent to the National Grid substation. The development of this project has involved a detailed design and engagement process which included numerous surveys and assessments to inform the plans which began in Spring 2022.

The project is an essential component to support the UK’s transition to net zero with the national transmission operator, National Grid, who have awarded Conrad Energy a contract to provide stability to the regional grid network and ultimately keep power flowing while reducing costs to the consumer. Traditional forms of generation such as large coal and gas-fired power stations have inherent network stabilising qualities. As these are phased out and we transition to renewable forms of power there is a decline in the stability of the system with greater fluctuation of power supply entering the grid, with Inertia and Short Circuit Levels falling. New sources of renewable energy such as wind and solar do not have the same stabilising qualities and therefore can cause stability issues within the national transmission network.

A synchronous condenser (sometimes called a synchronous capacitor or synchronous compensator) is a specialised piece of equipment that does not generate power but provides stability and voltage support to the electricity network, particularly when system faults occur within the power grid.

The location of the project is shown below or can be viewed on what3words’ interactive map here ///broadens.prom.wing.


In April 2019, National Grid, the Electricity System Operator (ESO) set itself the ambition of being able to operate the national electricity transmission network with zero-carbon by 2025.

At present a percentage of fossil fuel stations need to remain on the network at all times to provide necessary services such as inertia, voltage, frequency and short circuit level controls that help keep the network at its optimal operating levels.

National Grid ESO commenced an initiative known as ‘Stability Pathfinder Phase 3’ to find services to increase Inertia and Short Circuit Levels in England and Wales from 2025 onwards.

It is estimated that the cost to manage stability in England and Wales would cost an additional £14.9bn between 2025 and 2035 without these contracts in place. This is based on a comparison to the counter factual of the balancing mechanism over the 2025-2035 period, in which balancing actions such as constraints are used to maintain a percentage of fossil fuel power stations on the network to provide the equivalent inertia and short circuit level as provided by these contracts. These contracts are equivalent to six 300MW gas power plants, enabling the grid to remain stable without relying on fossil fuelled plants.

National Grid identified five ‘regions of need’ where there are stability issues on the network and issued a tender to procure services and proposals to deliver sustainable solutions.

The East of England has a significant amount of renewable generation. As such National Grid have identified this as a region requiring stability projects as part of the Pathfinder scheme.

National Grid has identified Grid Supply Points (substations) where there is space to connect the new equipment. Yaxley substation is one of those identified as suitable to support the Pathfinder scheme. It is one of few substations within the region that has the capacity to connect new technology. This means substantial cost and time savings and no further delays to the deployment of renewable energy across the UK.

Following research and assessments of options by Conrad Energy, the location at The Leys and Ivy Farm, Mellis Road has been selected as the most suitable site for its proximity to the substation, size and existing access.

We are always keen to work with communities local to our sites and have included details of how to contact us and be kept updated throughout the construction below. We will continue to update this webpage throughout the project to keep you informed.

Key facts

  • Access to the site during construction will utilise the temporary existing access track back to the A140 in place for the substation build. Once completed Conrad Energy will restore this track to the former land use (agricultural).
  • Operational traffic will use Leys Lane and is expected to be minimal with site visits planned for occasional maintenance via light van or 4×4 type vehicles.
  • To screen the site an extensive landscaping strategy has been commissioned with native hedgerows, woodland and wildflower planting are incorporated into the site design which also contribute towards local biodiversity measures. The site further benefits from existing screening on the southern side.
  • Employment generation is expected to be two full time staff, locally based, for the operation and maintenance of the plant.
  • Noise from the development will be minimal with mitigation measures incorporated such as the lining of the synchronous condenser building with a composite cladding system. A full noise impact assessment has been carried out which finds the development to have no impact on nearby sensitive receptors.
  • Proposed development is temporary and reversible, with a modelled operational lifespan of circa 35 years.

Proposed plans

Project timeline

August 2022

Planning submitted

Read the planning submission here

November 2022

National Grid ESO contract awarded

February 2023

Planning approval granted

March 2023

Updated (S73) planning application submitted

Read the planning submission here

June 2023

Updated (S73) planning application decision approval granted

August 2023

Construction starts



Community forum

The Yaxley Synchronous Condenser Community Forum is a regular meeting between representatives of the local community and other key stakeholders.

The intention is to provide a platform for Conrad Energy to deliver updates and to hear, consider and advise on issues that might affect the local community and key stakeholders as a result of the project. You can view presentations and minutes from the forum meetings below:

View the Terms of Reference that the forum operates under and the membership list here.


Synchronous condensers (sometimes called synchronous capacitors or synchronous compensators) provide stability and voltage support to the electricity network, especially when system faults occur within the power grid.

They do not generate power but produce or absorb reactive power to keep the current flowing consistently to the grid–helping to ensure reliable power is available for those who need it, when they need it.

The equipment is located within a steel framed, acoustically clad building, which is connected to a National Grid substation. Synchronous condensers do not generate any power.

Network stability is an inherent by-product of synchronous generation from coal and gas plants. As these fossil fuel plants are phased out and more power is produced from wind and solar, there is a decline in the stability of the system with inertia (mass of the system used to control frequency) and short circuit levels (amount of current that flows on the system during a fault) falling.

Synchronous condensers help stabilise and balance the grid in two key ways:

  • Inertia – Many generators producing electricity for the grid have spinning parts – they rotate at the right frequency to help balance supply and demand and can spin faster or slower if needed. The kinetic energy ‘stored’ in these spinning parts is our system inertia. If there is a sudden change in system frequency, these parts will carry on spinning – even if the generator itself has lost power – and slowdown that change (what we call the rate of change of frequency) while National Grid’s control room restores balance. Inertia behaves a bit like the shock absorbers in your car’s suspension, which dampen the effect of a sudden bump in the road and keep your car stable and moving forward.
  • Short circuit level – Short circuit level (SCL) is the amount of current that flows on the system during a fault. These faults can be caused by a lightning strike, weather conditions or equipment failure. During the fault, the system can see a direct connection to the earth and current flows from all sources into it. SCL is vital during such a fault as it helps us to maintain system voltage. If we get a disturbance, then a stronger system will dampen it out quickly. It is just the same as how a strong bridge with re-enforced joints would wobble but settle quickly when placed under force. If we operate a system with low SCL, it may take longer to recover after a disturbance.

The synchronous condenser will make a noise when operating, typically a buzzing or humming sound – similar to a substation. To minimise noise externally, the equipment will be enclosed within a steel building with acoustic cladding.

We have appointed a specialist noise consultancy to undertake a noise assessment for the site. The assessment has taken into account the existing sound levels in the area and considers how much any noise would be heard at various locations near to the site, including nearest properties.

The report demonstrates that noise levels at the nearest sensitive receptor would be acceptable.

The amount of EMF (electrical magnetic field) produced by a synchronous condenser is negligible, akin to a large generator.

Conrad Energy takes the issue of health very seriously. We believe it is right that the decision on what is acceptable or not is made independently of industry.

Accordingly, we design all our equipment to comply with the UK Health Security Agency’s recommended exposure guidelines. A vast amount of research has been done into the possibility of health effects, without establishing any risks below these levels.

The equipment will be housed within a 12m high warehouse, similar a large agricultural warehouse and to the adjacent National Grid indoor substation.

To reduce visual impact, we are proposing extensive screening and will explore opportunities for colouring of the building to meet the natural aesthetic.

We have carried out a detailed site assessment of the area around National Grid’s Walpole substation to identify where we could locate the synchronous condenser. We considered a number of factors, including proximity the national transmission system as well as potential impact on sensitive receptors such as residential or ecological sites, planning restrictions, topography and ground conditions. Following careful assessment of each option, the final site was determined to be the most appropriate on all accounts.

The proximity of the site to the National Grid substation was one of the key considerations. The effectiveness of the equipment is directly correlated to the distance between the condenser and the substation.

For optimum effectiveness the site should be located as close as possible. If the synchronous condenser was located further away, transmission losses within the cable and additional complexities would impact its effectiveness. In particular, the increased cable capacitance (electric charge within the cable) and negative effect on the reactive element would render the project significantly less effective in supporting the grid under fault conditions and it would therefore not be a viable option for National Grid.

Each application is assessed individually and where required a flood risk assessment completed to support a planning submission. This will assess whether there are any potential impacts and incorporate mitigation as necessary to ensure there is no increased flood risk from the development.

As part of the planning submission, we will provide details on the access route and number of predicted vehicle movements. The main impact would be during the initial phase of the construction works, when there would be a number of HGV movements. A Construction Traffic Management Plan is typically provided to support the planning process, setting out how we will manage and control vehicle movements to minimise any impact. Once operational, there will be negligible traffic movements as the site is monitored remotely with 1-2 weekly maintenance visits by a car or small van.

With all of our projects we want to make a positive contribution and enhance local ecology wherever we can. To achieve this an ecological survey is conducted to identify the conditions onsite. This informs our proposals and design. We look to incorporate a range of ecological enhancements. For example, it might include bird and bat boxes, bug hotels, tree planting and grass meadows. Local knowledge and feedback can play an important part in this.

The development is fully reversible, with an operational period of circa 35 years. The site would be fully restored to its existing condition on cessation of operations.

Over the past year, we’ve seen unprecedented increases in fossil fuel prices – with spiralling costs passed onto consumers already hard hit by the rising cost of living. European gas prices soared by more than 200 per cent. Russia’s invasion of Ukraine has piled even more pressure and the global situation has greatly exposed the UK and other European countries’ vulnerability with reliance on foreign imports of coal, oil and gas.

Human made climate change is the greatest threat facing the planet and its impacts are already being felt. The world is now warming faster than at any point in recorded history. From extreme weather events such as droughts and wildfires, record breaking rainfall and flooding, to the warming oceans, climate change is having an impact on our way of life across the world and closer to home too.

In order to tackle carbon emissions, we need to transition to a low carbon and clean energy system. The UK’s climate change ambitions are amongst the highest in Europe and require us as a nation to achieve net-zero greenhouse gas emissions by 2050. The British Energy Security Strategy (April 2022) set a target that ‘By 2030, 95 per cent of British electricity could be low-carbon; and by 2035, we will have decarbonised our electricity system’. More renewable energy generation and battery storage is needed to meet these targets.

For a clean, affordable and secure energy future the UK needs more renewables at home, and more storage – and it needs them quickly.

Keep in touch

We’d like to hear your feedback to help us shape our plans. If you have any questions please get in touch.

Email: yaxley@conradenergy.co.uk

Post: Yaxley c/o Conrad Energy, Suites D&E Windrush Court, Blacklands Way, Abingdon, OX14 1SY

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