Constraint management is required where the electricity transmission system is unable to transmit power to the location of demand, due to congestion at one or more parts of the transmission network. Here you can find out how to provide this service.

This service is geographically defined, so only certain providers will have the required technical capability to deliver the service. 

If the system is unable to flow electricity in the way required, we will take actions in the market to increase and decrease the amount of electricity at different locations on the network. 

Situations that can cause a transmission constraint 

  • Import 
    The energy demand cannot be met by localised generation and the flow on the circuits into that area is limited by the capacity of the circuits; or into that area is limited by the capacity of the circuits 
     
  • Export 
    The generation in the area is not offset by the localised demand and the flow on the circuits out of the area is limited by the capacity of the circuits 

These constraints can be further broken down: 

  • Thermal 
    Where the amount of energy that would flow naturally from one region to another exceeds the capacity of the circuits connecting the two regions. 
     
  • Voltage 
    Where generation is needed in a particular area to support the local voltage. 
     
  • Stability 
    Where particular circuit configurations have to be avoided because of the risk of oscillations in voltage or current. 
Technical Requirements

Constraint management requirements are identified based on a specific network need. 

We will outline the specific technical requirements for each service when a condition is identified. 

These could be: 

  • specific service times and dates; 
  • MW output; or 
  • ramp rates and reactive capabilities. 

The exact way in which a constraint is managed depends on a number of factors, including: 

  • the nature of the flows on the transmission system; 
  • the duration of the requirement; 
  • the local level of generation output; and 
  • local level of system demand. 

This means that each required service must fulfill a specific requirement stated in the tender. 

In general, this means that services must be provided in a particular location, i.e. only certain potential providers will have the required technical capability to provide the service. 

New Providers

Constraint management requirements are linked to specific system needs, so will be advertised ad hoc to match each requirement, rather than following a regular timetable. We will contact potential providers and, where there is sufficient competition, we'll seek to contract via a tender. 

In other circumstances, we will enter into bilateral contracts with service providers. 

Ahead of time contracts 

We can enter into contracts to agree output with a service provider ahead of time. 

Constraint management contracts enable us to agree in advance technical parameters with connected parties to facilitate the management of a constraint. 

The most common style of contract is to agree either a cap or collar on the output of a power station. 
While other commercial tools are available to manage the output of a power station, constraint management contracts are considered where the cost of the action is more economic than other commercial tools. 

There are multiple different styles of constraint management service that we may use to resolve a specific requirement. 

Existing Providers

Payments 

We will make payments following the standard settlement for balancing services, which is paid monthly. A final statement, along with the self-bill invoices, is issued by the eighteenth business day of the following month that the service was provided. 

The structure of the payment will be determined by the style of the constraint management contract required. 

Some examples of the possible payment rates are: 

  • utilisation fee £/MWh; 
  • a fixed £/settlement period fee; 
  • a £/settlement period fee for making a service available combined with a £/settlement period fee for use of the service; and 
  • a £/settlement period fee for making a service available combined with a £/MWh fee for use of the service. 
Document library

Static Reactive Power - Pennine - 2024-2034

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7 February 2022 - We have announced the results of the NOA Pennines High Voltage Pathfinder. Please see our results table and letter below for further information.

This tender has concluded. If you have any queries, please use [email protected]

Static Reactive Power - Mersey 2022 - 2031

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11.12.20 Please find an updated results letter and table for the Long Term Mersey Reactive Service tender 2022-31 and Lessons Learnt from the Mersey Pathfinder.

22.05.20 Please find the results letter and table for the Long Term Mersey Reactive Service tender.

20.03.20 Please see latest update for the tender participants for the Long Term Mersey tender

13.03.20 We have provided an update for the tender participants for the Long Term Mersey tender.

28.02.20 We have provided an update for the tender participants for the Long Term Mersey tender and an updated contract terms below.

31.01.2020 We have updated the Long Term Mersey Tender in the Invitation to Tender documents below.

Note: Please direct all queries and tender submissions to [email protected]

We have launched a long term tender for a Reactive Power service to meet a static need in the Mersey region. The 9-year contract, starting 1 April 2022, is part of a new approach to procuring reactive power to determine whether a third party can deliver a more economic solution compared to the network asset alternative. This tender is open to potential providers embedded within the Distribution network as well as at Transmission level, including those that are not yet connected.

Reactive Power Mersey 2021/22

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Please note we have provided an update in the letter below to the EOI responses that were received in Sept 2020 for the Short Term Static Reactive Power service for the Mersey Region.

An Expression of Interest (EOI) has been launched for a Reactive Power service to meet a static need in the Mersey region. The 1-year contract, starting 1st April 2021 with the potential for additional months. Please can you inform your interest by the 22nd September by responding to the EOI to [email protected]

Reactive Power - Mersey 2020/21

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A tender has been launched for a Reactive Power service to meet a static need in the Mersey region. The 1-year contract, starting 1st April 2020, is part of a new approach to procuring reactive power including potential new providers. This tender enables embedded assets, for the first time, to participate in a tender to solve a transmission voltage system need.

Stability Pathfinder Phase Two - Scotland 2020

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Updated 30 September 2020


We have published the Expression of Interest (EOI) for Stability Pathfinder Phase 2 which is our next step in finding new ways of keeping the grid stable and focuses on our long-term requirements in Scotland. This EOI invites providers to submit their proposals on possible solutions which would then be assessed. If successful, providers would then invited to carry out a feasibilty study ahead of the commercial tender. 

The EOI and associated documents can be found below. The deadline for responses is the 8th January 2021 and these must be sent to [email protected].

We will hold a series of webinars, details of which can be found in the Stability Pathfinder Phase 2 EOI V1 document.

Stability Pathfinder Phase One - GB 2020

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Last Updated 17/04/20

Thank you to all those who have participated or have taken an interest in Phase One. This tender is now complete and moving into the service delivery phase with contracts signed with the successful providers. The tender timeline was consciously ambitious for both providers and NGESO, and with an extension to the tender window and further due-diligence necessary ahead of signing contracts, has taken longer than initially anticipated. This has impacted the development of Phase Two and consequently we are not quite ready to publish an expression of interest (EOI) yet. We are now feeding lessons learnt from Phase One into the development of the timeline and approach for Phase Two. We are also now considering the potential implications of coronavirus on both our internal process and timelines, and the capability of prospective providers to participate in the next stage of procurement. Our system needs have not however diminished, and so we intend to commence Phase Two procurement later this quarter (Q2’20) with further details to be published as soon as possible.

South Wales and Mersey 2019/2020

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Request for Information

3rd October 2018 - We have published a Request for Information for the provision of Reactive Power Service in both South Wales and Mersey areas. The Request for Information forms part of our commitment in the Product Roadmap for Reactive Power. Interested reactive power providers are requested to submit information with an outline of their capability by the 5th November as detailed in the Request for Information. Please use the South Wales Proforma or Mersey Proforma in response to the RFI. 

Next steps update

4th December 2018 - The next steps for Request for Information for the provision of Reactive Power Service in South Wales and Mersey are published. Thank you to all providers who responded to the RFI, the information provided helped to shape the next steps of the RFI. The next steps can be found here for South Wales and Mersey

Tender

Following the publication of the Request for Information for the provision of reactive power services published on the website on the 3rd October 2018 and the update published on the 4th December 2018, please see below information regarding the next steps for the tenders in South Wales and Mersey

Scotland Enhanced Reactive 2019

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A tender has been launched for Enhanced Reactive Service in Scotland. The tender is to allow the Electricity System Operator to access reactive power capability beyond Grid Code Obligations. In this tender the focus is on reactive capability available when active power output is less than 20% of the rated active power output of the unit. 

For Information: Vector Shift - Loss of Mains Protection change

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FAO: Distributed Generators: Loss of Mains Protection change, away from Vector Shift (VS)

In order to preserve the stability of the electricity system, loss of mains (LoM) protection settings on a limited volume of existing generators fitted with Vector Shift (“VS”) type protection must be changed immediately in targeted locations across the south of England.

In order to encourage your support, the transmission system operator (TSO) and distribution network operators (DNOs) have agreed to a compensation proposal outlined in the open letters on this page, subject to generating units meeting the relevant criteria.

  • Is your site located in the SSE, UKPN or WPD DNO areas?
  • Is your distributed generation scheme sized at >1MW?
  • Is your protection afforded by a discrete G59 relay which utilises Vector Shift as its loss of mains protection?

Context and additional information is outlined in the open letters below.

Results

181 submissions were submitted to the DNOs and assessed by us. These sites accounted for over 1.3GW of Vector Shift capacity. All applications were ranked by their effectiveness at reducing the Vector Shift capacity at risk of trip, accounting for the cost, location, capacity and load factor during risk periods of each.

Two applications with incomplete information were excluded from the assessment.

Submissions from 71 sites, with a combined capacity of 811MW, met the assessment criteria and fulfilled our requirement at least cost to the consumer.

Latest news

7 February 2022 - We have announced the results of the NOA Pennines High Voltage Pathfinder. More information can be found on the Pathfinder webpage and the Market Information tab. 

30 September 2020 - We have published the Expression of Interest pack for Phase 2 of the Stability Pathfinder.

29 January 2020 - We have published the results of the tender for Phase One of the stability pathfinder. Results can be found on the Market Information tab. 
We would like to thank all those that participated in this world first tender. 

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Further enquiries

Get in touch with the right team within Balancing Services, who are on hand to answer any questions you may have.