Fast Frequency Reserve

The Fast Frequency Reserve (FFR) is procured to handle low-inertia situations. Inertia means the ability of the kinetic energy stored in the rotating masses in the electricity system to resist changes in frequency. The operation of the power system follows a dimensioning principle according to which the loss of a single electricity production unit or a HVDC link must not cause the frequency to fall below 49.0 Hz. The magnitude of the transient frequency change following a disturbance depends on the magnitude of the power change caused by the disturbance, the system inertia and the speed at which the reserves are activated. The needed volume of Fast Frequency Reserve depends on the prevailing inertia in the power system and the size of the reference incident.

The Fast Frequency Reserve has been implemented in the Nordics in May 2020. Fingrid procures the reserve from a national market. In order to participate in the market, the Balancing Service Provider has to complete the prequalification process of the Reserve Unit and sign the FFR market contract.

Technical requirements

The Reserve Units participating in the maintenance of the Fast Frequency Reserve must meet the technical requirements for the reserve. Compliance to the requirements must be demonstrated by prequalification tests before market participation.

The reserve power must be activated in full within the required time when the frequency falls below a certain value. The Balancing Service Provider can select any of the activation options listed in the table below.

Activation frequency (Hz)

Max. activation time (sec)








The minimum duration of activation is 5 seconds, if the power deactivation rate is no more than 20% of the FFR capacity per second.  If the deactivation rate is higher, the minimum duration of activation is 30 seconds. A Reserve Unit must be able to reactivate within 15 minutes of the previous activation.

The technical requirements and the verification of the regulation capability of the Reserve Unit are described in more detail in the document “The technical requirements and the prequalification process of Fast Frequency Reserve (FFR)”.



The need to procure a Fast Frequency Reserve depends on the inertia of the electricity system, so it is procured for only some of the hours and the volume to be procured may vary. The procurement need is highest in the spring, summer and autumn months at times when the amount of inertia is at its lowest. Fingrid publishes a procurement forecast one week ahead, see reserve market information.

Fingrid procures FFR from a national hourly market. On the hourly market, bids for the hours of the next day are submitted on the previous evening. The price of the reserve capacity is determined separately for each hour on the basis of the most expensive accepted bid.

The Balancing Service Provider may also submit a combination bid for Fast Frequency Reserve and Frequency Containment Reserve for Disturbances (FCR-D). The purpose of a combination bid is to enable flexible bidding for reserve capacity that is suitable for both reserve products. The capacity of a combination bid may be used for procuring either FFR or FCR-D. Also reserve capacity that participates in the Yearly Market of Frequency Containment Reserve for Disturbances can be offered to the Fast Frequency Reserve.