Market Court issued a decision on the cost determination principles for the grid protection system connected to Olkiluoto 3 production

In December 2024, the Energy Authority issued a decision on the cost determination principles for the transmission grid protection system connected to the production of the Olkiluoto 3 nuclear power unit (OL3). According to the decision, Fingrid, as the party responsible for the system protection, was entitled to charge TVO the majority of the costs incurred by the protection system as a service fee.

With today’s decision, the Market Court annulled the Energy Authority’s decision on the cost determination principles for the protection system and returned the matter to the Energy Authority for reconsideration.

According to the Market Court, Fingrid's responsibility for ensuring the operational reliability of the electricity system has, in practice, meant that Fingrid has been required to implement an arrangement similar to a system protection scheme.

According to the Market Court, the service has been incorrectly interpreted as a customer-oriented additional service requested by TVO.

- Considering the Market Court’s earlier decision in September 2025 concerning the responsibilities related to the protection system, this latest decision was expected. The decision confirms that Fingrid is required to implement a protection system for the grid. Now the protection costs will wait for a new decision from the Energy Authority. TVO’s position remains that the responsibility for developing and protecting the transmission grid lies with the transmission system operator Fingrid, and that the protection costs should therefore be covered through grid tariffs, says TVO’s Ulla-Maija Moisio, Senior Vice President, Legal Affairs.

On grid protection

In the view of national grid company Fingrid, the national grid is not currently ready for full-power operation (abt. 1600 MW) at OL3. The opinion of Fingrid is that with production exceeding the 1,300 MW power output level, the grid requires protection which will ensure the operability of the grid also in case abnormal conditions occur. At present, protection is implemented by reducing the consumption of specified industry consumers as well as by utilising e.g., battery storage plants.

Fingrid has in recent months on several occasions required that the power output of OL3 be reduced, because the protection operated by Fingrid has not been fully available. This may occur, for example, when an industrial business included in the protection system is undergoing a maintenance outage.

For more information, please contact:
Johanna Aho, Head of Communications, tel. +358 40 729 0822