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Reactive power services

Reactive power services are how we make sure voltage levels on the system remain within a given range, above or below nominal voltage levels. We instruct generators or other asset owners to either absorb or generate reactive power. Managing voltage levels comes from maintaining a balance between elements on the system, which either absorb reactive power (decreasing voltage) or generate reactive power (increasing voltage).

We use the services set out below to manage voltage levels:

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Obligatory reactive power service (ORPS)

Provision of varying reactive power output. At any given output generators may be requested to produce or absorb reactive power to help manage system voltages.

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Enhanced reactive power service (ERPS)

Provision of voltage support that exceeds the minimum technical requirement of the obligatory reactive power service (ORPS).

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16 April 2019 - We have also published a Request for Information for the provision of long-term reactive power service in Mersey starting from 2021/22. The deadline for submissions is 24th May. More context on this RFI can be found on our Network Development Roadmap page.

March 2019 - Long Term Reactive Power Needs out to 2031.
We are currently undertaking pathfinding projects looking at how we can tender for commercial solutions to future reactive power needs alongside considering asset options.
Find our more here

The Invitation to Tender and contract terms have now been published for the short-term Reactive Power Services out to 2021 in South Wales and Mersey. These can be found here: https://www.nationalgrideso.com/balancing-services/system-security-services/transmission-constraint-management?market-information 

The next steps for Request for Information for the provision of short-term Reactive Power Service out to 2021 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

We have published a Request for Information for the provision of short-term Reactive Power Service out to 2021 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. 


Reactive power describes the background energy movement in an alternating current (AC) system arising from the production of electric and magnetic fields. Devices that store energy through a magnetic field produced by a flow of current are said to absorb reactive power; those that store energy through electric fields are said to generate reactive power.

The flows of reactive power on the system will affect voltage levels. Unlike system frequency, which is consistent across the network, voltages experienced at points across the system form a 'voltage profile', which is uniquely related to the prevailing real and reactive power supply and demand. We must manage voltage levels on a local level to meet the varying needs of the system.

Without the appropriate injections of reactive power at the right locations, the voltage profile of the transmission system will exceed statutory planning and operational limits.