Standard tests and requirements for rate-of-change of frequency (ROCOF) measurements in smart grids

Short Name: ROCOF, Project Number: 15NRM04
Image showing power lines and wind turbines in autumn sunlight
Power lines and wind turbines in autumn sunlight

Supporting growth of renewably-sourced energy and supply grid resilience

The use of renewable energy systems (RES) is increasing, with the next EU target set at 32% of energy consumed across Europe coming from renewable sources by 2030. However, adapting to the corresponding drop in system ‘inertia’ is a complex and costly challenge.

Conventional large thermal generation systems are powered by heavy, high-inertia turbines that rotate at reliable frequencies. If they power down, they do so gradually, causing only slow fluctuations to the network’s frequency and giving operators time to react. Contrastingly, RES tend to offer far less ‘inertia’ and risk imposing rapid changes to system frequency.

The rate at which the power quality of an electric system changes is called the ‘rate-of-change of frequency’ (ROCOF) and is used to assess sub-second control decisions. However, measurements of ROCOF are susceptible to disturbances and other effects typical in real networks. Prior to the ROCOF project, improved techniques to measure ROCOF had been proposed, but not realised, and new methods to control frequency were becoming more critical for managing increasingly volatile networks.


This project has built on the achievements in EMRP projects SmartGrid and SmartGrid II and developed new ways to measure ROCOF in electricity networks, starting by compiling a library of electricity supply grid measurements relevant to power quality. These were used to develop algorithms to accurately measure ROCOF under network conditions through computer simulations and laboratory testing. This led to development of compliance verification protocols for ROCOF instruments and predicted uncertainties, developed using Monte-Carlo simulations.

These results influenced the International Electrotechnical Commission to produce a draft technical standard, which will cover all new renewable generators and large storage farms throughout the world, defining the way they lock on to the grid frequency. Project outputs contributed to three out of five new chapters of the standard.


The outcomes of the project will help utility companies to maintain the stable operation of RES across their networks and increase network resilience, supporting the transition to green energy sources.


Project website
Field Measurement of Frequency and ROCOF in the Presence of Phase Steps

IEEE Transactions on Instrumentation and Measurement

PMU-based power system analysis of a medium-voltage distribution grid

CIRED - Open Access Proceedings Journal

The Case for Redefinition of Frequency and ROCOF to Account for AC Power System Phase Steps

2017 IEEE International Workshop on Applied Measurements for Power Systems (AMPS)

Other Participants
University of Strathclyde (United Kingdom)