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National Grid ESO's Electricity National Control Centre. Image: National Grid ESO.
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A ‘milestone moment’: National Grid ESO’s Faye Relton takes a look back at DCs first year

National Grid ESO's Electricity National Control Centre. Image: National Grid ESO.

It’s a little over a year since we rolled out our new Dynamic Containment (DC) service in the National Grid Electricity System Operator (ESO) control room – a milestone moment in reforming our frequency response services.

DC launched on 1 October 2020 as a low frequency response service, significantly boosting ESO’s ability to respond rapidly to disturbances in the flow of electricity around the grid – specifically those caused by large generation losses.

The service got an early work out less than 24 hours after launch, when the 139MW of battery capacity taking part in the first auction was called on to respond to an interconnector tripping while importing 1,000MW.

DC units responded in under a second to help the system frequency return to safe operational limits, and have done so on a further 15 occasions in response to significant frequency events.

There have been several key developments since the launch of the service, from the introduction of balancing mechanism stacking to the recent move to automated, more granular EFA block procurement on a pay-as-clear auction platform. Prior to the move to the new platform in September we’d accepted 182,499MW of Dynamic Containment low frequency (DCL); we’ve since procured a further 271,000MW.

This move to the EPEX platform followed a long-running ESO innovation project trialling closer to real-time procurement of frequency products, and is an ideal interim solution while we tender for an enduring auction capability – once which will continue widening access to frequency response markets.

Already we’ve seen the new granular procurement approach deliver a lower average price – just under £14/MWh – compared with the steady £17/MWh we’d seen since launch, demonstrating how competition is increasing and value for the consumer improving.

We’re now reaching an exciting phase in the service. In November we introduced Dynamic Containment high frequency (DCH) to further strengthen our operational capability to respond to significant frequency events.

Where DCL mitigates against large generation losses – which would see the frequency fall – the new DCH product will respond to large demand losses which might cause the system frequency to rise, soaking up power to catch the frequency deviation.

To date we’ve procured 15,600MW, and those megawatts have already been put to the test: an interconnector tripped last week while exporting 1,000MW, with DCH safely containing the frequency jump to within our statutory range.

Large demand loss risks occur less often than large generation loss risks – particularly over the winter period – so we anticipate the need for DCH occurring less often than DCL. Like DCL, the requirement for DCH varies across the day, and there may be EFA blocks with no requirement for the service.

Dynamic Containment is the first service we’ve introduced in our planned suite of fast-acting products to manage system frequency second by second.

We’re currently consulting with industry and stakeholders regarding the next two products – Dynamic Moderation (DM) and Dynamic Regulation (DR) – both of which are expected to launch in spring next year.

Where DC is required to act post-fault to keep frequency within statutory limits (±0.5Hz), DM is being designed to deliver rapidly pre-fault to help our control room keep frequency within operational limits (±0.2Hz) – mitigating sudden large imbalances by responding quickly when frequency moves towards the edge of that operational range.

DR is another pre-fault service designed to correct continuous but small deviations in frequency to regulate it around the 50Hz target. So this is about slower, proportional response that is continuously delivered. In comparison to DC and DM, assets delivering DR will not need to respond as rapidly, but they must have a duration of service that supports continuous operation.

The whole suite together will be crucial in delivering rapid and real-time management of frequency as we operate an electricity system with more zero carbon generation and less inbuilt inertia.

Alongside projects like our stability pathfinder and Accelerated Loss of Mains Change programme, the service is central to securing a future low carbon grid and enabling that first period of carbon-free system operation by 2025.


Faye Relton Ancillary services development manager, National Grid ESO

Faye Relton is ancillary services development manager at National Grid ESO


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