Losing Nemo: Flexibility providers jump into action for grid stability

 In News

A fault at one of the UK’s most high profile interconnectors has once again highlighted the vital role that flexibility providers have to play in maintaining grid stability and the country’s energy security.

On Monday 24 February, the frequency of the UK’s electricity grid dropped to 49.58Hz – within just 0.1Hz of its minimal operational limit.

The unplanned outage was caused when the Belgium interconnector named Nemo Link, which was commissioned just over a year ago, tripped while importing at full capacity (1GW).

Nemo Link has the potential to provide power for one million homes and is one of a handful of new interconnectors being built between Britain and continental Europe, which are designed to increase the UK’s power supply flexibility.

While National Grid ESO will at times reduce the flow of these interconnectors, Nemo Link was not subject to any ‘Rate of Change of Frequency (ROCOF)’ constraints at the time. The result being a drop in power causing an imbalance for the UK and a surplus in generation for Belgium.

How did National Grid manage the Nemo loss?

National Grid is obligated to maintain UK grid frequency at 50Hz, plus or minus 1%, as anything outside of these limits risks damaging infrastructure. In order to do so, the system is continuously monitored and controlled second-by-second, to ensure a balance is achieved between supply and demand.

When Nemo tripped, Upside Energy and other flexibility providers were instantly called into action. A portfolio of frequency response assets, including Open Cycle Gas Turbines, pumped hydro and batteries, helped back up the system in real-time, until assets in the balancing mechanism and short-term-operating reserve contracts ramped up.

The quick response of these assets led to normal frequency levels being recovered within one minute, with no loss of supply on the system.

Maintaining a stable grid

While rare, events such as the Nemo loss are not uncommon. This includes 1GW falling off the system in May 2019 when the French interconnector tripped, resulting in grid frequency falling to 49.63Hz.

What such events continue to highlight is the vital role that flexibility providers have to play in helping maintain a stable grid.

As renewables form an increasingly large part of the energy mix and traditional power stations are decommissioned, the UK’s electricity system is experiencing lower inertia, and bigger and more numerous losses in frequency. This is something which has been recognised by National Grid.

To manage this, the operator is aiming to deliver a new suite of faster acting frequency response products. Through its Stability Pathfinder initiative, National Grid is also working on creating markets for inertia – as managing low inertia is going to be paramount to achieving its target of a zero carbon electricity system by 2025.

Upside in action

With batteries increasingly being called upon to help maintain grid frequency – and the growing use of renewables set to increase this need yet further – such assets are working harder than ever. This raises some important usage considerations for asset owners, particularly in relation to warranties.

At Upside Energy, we support storage asset owners and maintenance operators to not only take part in DFFR, but to ensure they are using their assets in the most beneficial way.

The Upside Virtual Energy Management System (VEMS) monitors the utilisation of assets when running a DFFR contract, or other commercial services. It provides real-time diagnostic and monitoring tools for storage and distributed generation asset owners.

These services are aimed at measuring asset storage performance in order to ensure the battery is performing in line with manufacturer warranty conditions, but also to help quickly diagnose and alert operators to any unforeseen operational incidents.

UK powercut