Transmission System

Delivering the world’s first accurate and continuous inertia measurement service

The Energy Transition Poses Significant Challenges for TSOs

This short, animated video describes the challenge of declining system stability that Transmission System Operators (TSOs) face as part of the renewable energy transition.

It highlights the importance of real-time inertia measurements to enable TSOs to optimize their balancing reserve procurement and to utilize more renewable generation.

Giving TSOs Unique Insights

GridMetrix® enables TSOs to move from increasingly inaccurate inertia models to real-time, direct inertia measurements.

As we move rapidly towards renewables 2.0, this real-time visibility of critical network conditions will empower TSOs to make key commercial and operational decisions faster, safer and more cost-effectively.

Reactive, together with our partners, National Grid ESO and Tokyo Electric Power Company, are setting the global power grid inertia standards for the next generation of system stability management.


“As the penetration of wind and solar on the system increases, operation of the system becomes significantly more complex. The power system is being operated closer to its known limits more frequently, with increasingly variable and uncertain supply and demand, and declines in system strength and inertia


National Grid ESO Logo

Zero carbon operation of the electricity system means a fundamental change to how our system was designed to operate; integrating newer technologies right across the system… using new smart digital systems to manage and control the system in real-time.


Terna Logo

Innovation and digitization, required to cope with the increased complexity of the system, are one of the two enabling factors of our strategy and we plan to devote around EUR 900 million to these initiatives…this represents a paradigm shift: from Watts to Bytes.

National Grid and Reactive – Developing World Leading Solutions

Duncan Burt, Acting Director of Operations at National Grid in the UK, discusses the fruitful relationship between Reactive Technologies and National Grid ESO that has led to two technological world firsts.

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Estimation Methodology Summary

The three inertia estimation models shown in the table below provide static and historic views of system stability only. None offer a controllable, accurate and continuous view of inertia from transmission, distribution and demand – a view needed by grid operators to safely integrate greater amounts of renewable generation and maintain system resilience. An innovative direct and continuous inertia measurement methodology powered by Reactive technology now, for the first time ever, enables TSOs to have a real-time, accurate view of inertia.

Accurate Power
Enough data to understand inertia patternsAccurate RoCoF
Summing inertia across all synchronous generatorsN/AN/A
Calculating RoCoF during large frequency excursions
Estimation based on power events throughout the day
gridmetrix logoReal-time inertia measurement

Transformative for TSOs

GridMetrix® gives TSOs the inertia visibility they need to operate their systems in the new, more
intermittent energy mix.

proven technology


Deployed and successfully demonstrated internationally with multiple TSOs with highly accurate results delivered

increased renewable integration

Increased Renewables Integration

An accurate view of inertia will allow TSOs to reduce the need to curtail intermittent generation in lieu of fossil fuels and ultimately accommodate more renewables.

decreased spend

Decrease Unnecessary

By better understanding their grids, TSOs will be able to make more informed procurement decisions.

secure clean tech

Maintain Security
of Supply

Having real-time visibility events propagating through their networks will allow TSOs to take optimal mitigation/recovery steps and continue to keep the lights on.

gridmetrix inertia measurement technology

gridmetrix logo

GridMetrix for TSOs

Reactive’s novel intentional power stimulation method is combined with bespoke gridedge measurement units and a cloud analytics platform. This delivers Transmission System Operators unparalleled visibility of inertia.

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Downloadable resources

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    GridMetrix Flyer

    Overview of Technology Benefits

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    Cigre Paper

    Reactive's paper on inertia measurement