Connecting European Grids – Supporting Energy Security
ENTSO-E power grid is composed of 8 synchronous zones: Continental Europe, Baltic, Nordic, British, Irish, Sardinia-Corsica, Cyprus, and Crete. Each synchronous area has its own control block leaders who are responsible. When ENTSO-E was established in 2009, it was given specific legal responsibility to enhance technical cooperation across the synchronous areas. Since then, it has established legal rules, called Network Codes and Guidelines, which seek to harmonise system operations ensuring secure coordination.
The Continental Europe Synchronous Area (CESA) is the largest of the synchronous grid (by connected power) in the world. The synchronised frequency is 50 Hz and the area supplies over 400 million customers in 24 countries, including most of the European Union. Transmission system operators (TSOs) in CESA have the responsibility to maintain the frequency at 50 Hz in order to ensure the stability of the system. This means energy resources and consumption always must be balanced across the synchronous area.
CESA has increased its scope in 2015 with Turkey, in 2022 with Ukraine & Moldova and in 2025 with the Baltic countries of Lithuania, Latvia and Estonia. The synchronous area is supported by a Synchronous Area Framework Agreement (SAFA) which binds all connecting TSOs with a comprehensive rule book.
On 27 February 2022, Continental Europe TSOs have received a request from Ukrenergo (Ukrainian TSO) and Moldelectrica (Moldovan TSO) for an emergency synchronisation with the Continental Europe power system, which was supported by EU Energy Ministers. Continental Europe TSOs committed to respond positively to Ukrenergo’s request and started analysing the conditions for an emergency synchronisation while maintaining the safety of the Continental Europe power system. On 11 March 2022, Continental Europe TSOs concluded that the conditions for an emergency synchronisation were met and completed the emergency synchronisation on 16 March. Throughout the process Continental Europe TSOs receive support from the European Commission, the Member States and Regulatory Authorities.
The Project for the synchronisation of the Ukrainian-Moldovan power systems with the one of Continental Europe started in 2017. The Project included a Catalogue of Measures to be completed before being able to proceed with the synchronisation. The emergency synchronisation allows for interconnection without all measures being completed but by ensuring additional mitigation measures to limit the operational risks. It will allow supporting Ukrenergo and Moldelectrica in maintaining the stability of the Ukrainian and Moldovan power systems.
Continental Europe TSOs identify certain risks related to Protection and Dynamic Stability, Operations and Markets, Legal and Regulatory, and Information Technology including Cybersecurity. Exceptional actions have been implemented with the support of concerned stakeholders and authorities. A comprehensive 24/7 monitoring of the situation is foreseen, and appropriate measures are also planned depending on the evolution of the situation in Ukraine.
Former EU Commissioner for Energy Kadri Simson said:
Connecting European Grids – Supporting Energy Security Sonya Twohig – Secretary-General, ENTSO-E The synchronisation of the grids was not only a very important achievement for securing energy supplies for both Ukraine and Moldova. It was also a strong political symbol of our support, and that remains the case today. Throughout the difficult years of war in Ukraine, our cooperation with Ukrenergo has been seamless. I would therefore also want to pay tribute to the extraordinary efforts and skills of Ukraine in keeping the system running and carrying out repairs in the face of Russia’s targeted attacks against energy infrastructure.
Speaker
Sonya Twohig is the Secretary-General of ENTSO-E, the European Network of Transmission System Operator for Electricity, the Association of 40 TSOs in Europe who provide security of supply to over 500 million customers. In this role, she fulfills the mission of the European Transmission System Operators (TSOs) to deliver on the European goals of achieving a carbon neutral continent by 2050.
As Secretary General, she has a direct role in fostering technical cooperation between system operators, furthering Regional Coordination and ensuring security of supply and resilience across Europe. A critical milestone was achieved in March 2022, shortly after the invasion by Russia and in solidarity with the people of Ukraine where ENTSO-E TSOs decided to accelerate the connection of the power systems of Ukraine and Moldova with the Continental European System. Furthermore, on 9 February 2025, ENTSO-E connected the Baltic countries with CE Power system.
Prior to joining ENTSO-E, Sonya Twohig held several senior management positions in EirGrid Group in the areas of Markets, System Operations and Grid Development. She has master’s qualifications in physics, engineering science and business administration including executive diploma in corporate governance.
About Energy Futures Lab
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