Glossary

mFRR (Manual Frequency Restoration Reserve)

mFRR is a tertiary regulation reserve of net power and frequency used to restore a balance between the supply and demand for electricity in the case of medium- to long-term deviations in the power system. The goal of the mFRR is to maintain frequency within set limits and stabilize the system when previous regulation mechanisms (e.g., aFRR) are insufficient to address the deviation.

How does the mFRR work?

  • Manual activation: mFRR is manually activated based on instructions from the distribution system operator (e.g., SEPS in Slovakia).

  • Response time: Activation typically begins approximately 12.5 minutes after the instruction is given.

  • Function: The system is used for longer-term correction of power, either by increasing supply during shortages, or decreasing it during periods of excess. The aim is to achieve a stable frequency of 50 Hz in the grid.

mFRR plays a key role in ensuring a balance between generated and consumed power over a longer period. It is particularly crucial during unexpected events which cause significant deviations, such as the failure of large generation sources or sudden changes in consumption.