Transmission constraint management

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.

We understand generators working under the Accelerated Loss of Mains Change Programme may be restricted by Coronavirus. If you are struggling to meet the deadline, keep in touch for updated advice to be published shortly.

Overview and Service Updates

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.

Latest News

6 April 2021We have issued an updated Pennine tender information pack (v1.1) to clarify the effectiveness values found on slide 29. This can be found on the Market Information tab.

26th March 2021 - We have published the tender for the Long Term Reactive Power Service contracts for the Pennine region for 10 years starting 1 April 2024. It is part of a continued 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. The tender details can be found on the Market Information tab. The deadline for technical submissions is Friday 14 May 2021. 

11 Dec 2020 - We have published a revised set of results for the Long Term Reactive Power Service contract in the Mersey region starting in April 2022. The results can be found on the Market Information tab. In addition we have also published Lessons Learnt for this tender and would like to thank all those who supported the development of the Lessons Learnt.

30 September 2020 - We have published the Expression of Interest pack for Phase 2 of the Stability Pathfinder. This can be found here and the deadline for responses is 5pm on 8 January 2021.

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.

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.

Situations that can cause a transmission constraint


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


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:


Where the amount of energy that would flow naturally from one region to another exceeds the capacity of the circuits connecting the two regions.


Where generation is needed in a particular area to support the local voltage.


Where particular circuit configurations have to be avoided because of the risk of oscillations in voltage or current.