CESA (Continental European Synchronous Area)

The Continental European Synchronous Area (CESA) is the largest of Europe's synchronous electrical areas — a single 50 Hz alternating-current zone in which all connected systems share the same frequency in real time. It covers around 26 countries from Portugal to Greece, plus the Western Balkans, and from 9 February 2025 also Estonia, Latvia and Lithuania.

Governance

CESA is governed under the System Operation Guideline (Commission Regulation (EU) 2017/1485). The synchronous area is divided into LFC blocks (Load-Frequency Control blocks), each consisting of one or more LFC areas — typically a TSO's control area. Each block keeps its own FRCE within Level 1 / Level 2 ranges, sizes its own FRR and RR reserves, and operates an LFC Block Operational Agreement.

Baltic synchronisation

The Baltic states desynchronised from the Russian/Belarusian IPS/UPS grid (the BRELL ring) on 8 February 2025 and synchronised with CESA at 14:05 EET on 9 February 2025, after years of preparation. Estonia, Latvia and Lithuania now form the joint Baltic LFC block within CESA, with Elering, AST and Litgrid each operating their own LFC area inside it.

What changed for Estonia

Frequency control, reserve sizing and balancing rules now follow Continental ENTSO-E standards, not the Russian-led BRELL framework. To compensate for the lower rotational inertia in the smaller Baltic block, three synchronous condensers were commissioned in Estonia, plus one each in Latvia and Lithuania. Operational membership in MARI, PICASSO and IGCC followed in 2024–2025.

Sources

System Operation Guideline (Reg. (EU) 2017/1485) · Elering: Synchronisation with Continental Europe · ENTSO-E: Regional Groups