On January 21, 2021, JSC "Augstsprieguma tīkls" together with the other Baltic transmission system operators (TSOs) prepared and published the Baltic Load-Frequency control block (LFC block) concept, which described plans for establishing and implementation of methodologies and processes necessary for operation of Baltic LFC block.

In order to maintain safe and effective operation within the Baltic LFC block, frequency restoration reserves (FRR) will be dimensioned and ensured in accordance with the Baltic FRR dimensioning methodology (hereinafter – Dimensioning methodology).

Purpose of Dimensioning methodology is to ensure sufficient FRR volumes to be procured by Baltic TSOs to regulate Baltic LFC block FRCE (frequency restoration control error) towards zero and to ensure operational security. Baltic FRR dimensioning methodology is based on the combination of probabilistic and deterministic methods. Probabilistic approach estimates necessary FRR capacities based on the historical data. The deterministic approach defines must-have FRR capacity to at least cover the reference incident of Baltic LFC block. The principles are developed considering requirements of SOGL and SAFA.

Baltic TSOs have developed and publicly consulted the Dimensioning methodology, after which it was submitted to Baltic national regulatory authorities for approval. Within the methodology the Baltic TSOs foresee long-term dimensioning process, that takes place yearly, publishing the results by August of previous year.

Therefore, the Baltic TSOs have estimated the Baltic FRR demand for the year 2025 in the amounts summarized in the table below.

This estimation indicates the preliminary largest possible amounts of reserves needed within the LFC block that shall be ensured by performing a common procurement of reserves in Baltic balancing capacity market. The values may vary during the year. From the indicative volumes part of reserves will be procured as aFRR. Capacities of aFRR shall vary symmetrically in upward and downward regulation directions in the range of 90 MW to 120 MW depending on the time of the day. The remaining amount of FRR shall be procured in form of mFRR capacity.