Estonia / Finland: A fault during testing at Estonia’s 100 MW Kiisa battery energy storage system led to a major disturbance in the regional power grid on 20 January, shutting down both EstLink 1 and EstLink 2 connections between Estonia and Finland.
The incident resulted in the sudden loss of around 1,000 MW of capacity, equal to roughly 20 % of the Baltic region’s winter electricity demand. Initial support was provided by the continental European grid, with the 500 MW AC link between Poland and Lithuania temporarily operating at double its rated capacity. Reserve generation within the Baltic states was later activated.
According to Estonia’s transmission system operator Elering, the disturbance was caused by oscillations originating from a device connected to the main grid whose behaviour did not meet network requirements. The event occurred during final grid-connection testing at the Kiisa battery park, triggering trips on the DC cables.
The $118 M (€100 M) facility, located south of Tallinn, is being developed by Evecon together with Corsica Sole and Mirova. It includes 54 battery containers supplied by Nidec Conversion and connects to the grid via Estonia’s first 330 kV underground AC cable. Full commissioning is planned for early 2026.
Evecon confirmed that the device referenced by Elering belonged to the Kiisa project, stating that the issue arose during configuration and testing rather than normal operation. The company said responsibility currently lies with the technology supplier, which remains in charge until final commissioning.
Elering described the incident as a key learning moment following the Baltic states’ desynchronisation from the Russian power system, particularly as more inverter-based technologies are connected to the grid.
Source: PV Magazine
