Grid Constraint Event

On 20 January 2026 a disturbance in Estonia's power system caused both EstLink 1 and EstLink 2 converter stations to trip offline simultaneously, resulting in the loss of roughly 1,000 MW of cross-border transfer capacity within seconds — equivalent to about 20% of the Baltic region's winter electricity load and described as the most severe disturbance to the regional power grid since desynchronization from the Russian electricity system. The 500 MW AC connection between Poland and Lithuania compensated by operating at double its rated capacity while Baltic reserve capacity was deployed to restore the balance between production and consumption. The oscillations were traced to the 100 MW / 200 MWh Kiisa battery energy storage facility (the Hertz 1 battery park, owned by Estonian developer Evecon in partnership with Corsica Sole and Mirova) during its final grid-connection testing phase. Elering identified the trigger as a device connected to its main 330 kV grid whose behaviour did not comply with network requirements; Evecon subsequently confirmed the device belonged to the Kiisa battery park and attributed primary responsibility to technology provider Nidec Conversion, which was running the configuration and testing programme before the system's planned 3 February 2026 commissioning. Elering described the incident as a significant learning experience for the Baltic region following desynchronization from the Russian electricity grid.