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 49.8 to 50.2 Hz.
Transmission system operators ensure electricity balance by using the regulation service. More information about system regulation types can be found here.
The Baltic electricity transmission system operators (TSOs), operating in synchronous mode with the European energy system, must independently ensure frequency regulation and continuous, precise balancing of consumption with electricity supplies.
Until 8 February 2025, the Baltic States operated in a unified synchronous zone with the unified Russian power 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 expired on 7 February 2025.
On 8 February at 9.09, the Baltic operators disconnected the Estonian, Latvian and Estonian power systems from the IPS/UPS grid and, after conducting an isolated operation test, on 9 February 2025 at 14.05, the Baltic States' energy system were synchronously connected to the continental Europe's energy system.