Transmission System Operator

Transmission System Operator

The Transmission System Operator, also called TSO, is an essential part of the electricity supply chain. It is responsible for managing and operating the high-voltage power grid that transports electricity from power plants to local distribution networks.

The distribution networks are managed by a distribution system operator, called DSO. The DSO then transports electricity to homes and businesses. The DSO organizes a local market while respecting an exchange power schedule agreed with the TSO. The TSO has no access to the resources connected to the distribution grid.

Diagram of the interconnection of DSO and TSO

Main Responsibilities of the TSO

The TSO is responsible for maintaining the stability and reliability of the transmission network, balancing electricity supply and demand, and ensuring that electricity flows smoothly through the network.

The TSO plays a crucial role in maintaining the security of electricity supply. It must constantly monitor the grid for signs of instability or potential problems and take action to prevent outages or blackouts. It must also ensure that the grid can cope with sudden changes in demand, such as during periods of high electricity consumption or when a power plant unexpectedly goes offline.

The imbalances in the grid can be resolved by implementing ancillary services. Ancillary services (AnS) refer to various support services that are necessary to maintain the reliability and stability of the power grid, such as the balancing of supply and demand on the grid.

The TSO also manages the connection of new sources of electricity generation, called generators, for example, solar farms, to the grid and oversees the construction of new transmission infrastructure.

Besides generating energy and selling it to traders, producers can also provide ancillary services to help TSOs balance the transmission system.

TSOs Help with the Transition to More Sustainable Energy

The TSO also plays an important role in facilitating the transition to a cleaner and more sustainable energy system. As more renewable energy sources are being used, the TSO must adapt the grid to accommodate these sources by investing in more modern infrastructure and expanding the grid.

The TSO uses advanced forecasting tools to predict the output of renewable sources, such as wind or solar, and plan the expected fluctuations in supply and demand. 

TSOs also ensure that the grid remains balanced while using energy from renewable sources by matching supply with demand in real time. They do this by using flexible resources like energy storage, demand-side response (DSR), and flexible generation, and also by balancing using cross-border energy by exchange with other TSOs, to manage fluctuations in supply and demand.

This is another responsibility of a TSO to manage the integration of new technologies, such as energy storage systems or demand-side response programs, which allow electricity consumers to adjust their energy consumption and can help make the grid more resilient.

European Network of Transmission System Operators for Electricity

In Europe, the TSOs form an association called the European Network of Transmission System Operators for Electricity, in short ENTSO-E. The association consists of 39 members from 35 countries. 

ENTSO-E has the responsibility of ensuring the safe and coordinated operation of Europe's electricity system, which is the largest interconnected electrical grid globally. It serves as a technical cooperation platform and facilitates seamless electricity trading. Trading of electricity among TSOs helps with the resilience of the grid as it helps with balancing the supply and demand in real-time.


In summary, the transmission system operator is a critical part of the electricity supply chain, responsible for managing and operating the high-voltage electricity grid. Its role is to ensure that electricity is transported safely and reliably from power stations to the distribution system operator and then to homes and businesses, while maintaining security of supply and facilitating the transition to cleaner and more sustainable energy.

List of Transmission System Operators in Europe

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