Inertia Measurement

World’s first inertia measurement

National Grid UK and Reactive Technologies partnered on an innovation project called SIM (System Inertia Measurement) that in 2017 conclusively proved Reactive’s GridMetrix is the first technology in the world capable of accurately and directly measuring grid inertia 24/7 across a national grid network in a safe, reliable, and cost-effective manner.

Duncan Burt, Acting Director of Operations at National Grid in the UK, describes what the consequences would be of not addressing the inertia challenge.

The challenge of declining inertia

Historically power grids were supplied by large power stations. These contain large rotating mass in the form of turbines which in turn supply inertia to the grid. Inertia is important as it acts as a ‘shock absorber’ for frequency, allowing the Grid to ‘ride out’ issues. Renewables don’t have these turbines, so as the uptake of renewables increases, inertia drops and grids become more volatile.




The importance of measuring inertia

Until recently, direct power grid inertia measurements have not been possible so instead grid operators have relied on inertia estimates. Unreliable inertia estimates and models currently result in considerable energy reserve services procurement overspend, inefficient and costly network reinforcement and unnecessary curtailment of renewable generation output.

How does Reactive measure inertia?

Reactive’s cutting-edge signalling technology enables the transmission of data signals across an entire national grid infrastructure for the first time. It was during the development of this technology that we realised the potential to add grid measurement and deep dive analytics capabilities.

For more information on our technology, please visit our GridMetrix page.

Benefits of inertia measurement

There are significant benefits to be gained by grid operators implementing GridMetrix and therefore moving from inertia estimates to direct and continuous measurements:


Actions to either increase inertia or reduce (trades) the maximum infeed loss can be taken in advance with confidence


With enhanced grid awareness, TSOs can offer response products with sub-second delivery to address increased system volatility

Infrastructure investment

By having visibility of critical data points, TSOs are better able to identify the most optimal locations to reinforce the network

Operational planning

TSOs are provide with up to 36hr ahead forecast with refinement 4-5hrs from real-time allowing them to make informed actions to manage Rate of Change of Frequency (RoCoF)

Want to hear more?

To learn more about our solutions and to set up a meeting to see how we can benefit you, please drop us a line.