Transmission system operators are responsible for the reliability and stability of the electricity system, including by providing a continual balance between electricity generated and consumed. Any deviation from this balance causes a system imbalance. The indicator of electricity balance is electricity frequency. In the Baltics, in normal operating mode, the frequency must be within a range from 49.95 to 50.05 Hz.
Transmission system operators ensure electricity balance by using the regulation service. More information about system regulation types can be found here.
At present, the Baltic States operate in a unified synchronous zone with the unified Russian electricity system - UPS (Unified power system of Russia) in accordance with mutually concluded contracts between countries (Belarus, Russia, Estonia, Latvia and Lithuania) included in the BRELL transmission system. The BRELL agreement will be rendered invalid on 7 February 2025. On 8 February 2025, Baltic operators will disconnect the energy system of Estonia, Latvia and Lithuania from the IPS/UPS grid and perform an isolated operational test of the Baltic energy system. After the completion of the test, on 9 February 2025 the Baltic States' energy system will synchronously connect to continental Europe's energy system. Upon commencing synchronous operations with the European energy system, the Baltic States' transmission system operators perform (PSO) will be required to independently provide frequency regulation and continuous precise balancing of consumption with electricity supplies.