System Shock: The January 20 Incident
On January 20, the Baltic power system faced a sudden and severe technical disturbance. A disruption in Estonia’s grid triggered the emergency shutdown of both EstLink submarine cables connecting Estonia and Finland.
The fault resulted in the instantaneous loss of approximately 1,000 MW of power. This figure is significant, representing roughly 20% of the entire Baltic region’s winter electricity load.
To bridge this massive deficit, the continental European grid provided immediate support. The 500 MW AC connection between Poland and Lithuania was forced to operate at double its rated capacity to compensate.
Reserve capacity within the Baltic states was subsequently deployed to stabilize the grid. While a total blackout was avoided, the event exposed vulnerabilities in the region’s evolving energy infrastructure.
The Trigger: A Battery Giant on Test
Investigations quickly identified the source of the oscillations: a facility in Kiisa, just south of Tallinn. This site houses one of the largest battery energy storage systems in the Baltics, with a capacity of 100 MW/200 MWh.
The incident occurred during final grid connection testing. The testing process triggered unexpected power oscillations, which caused the DC cables to trip for protection.
The €100 million facility is being developed by Estonian energy company Evecon in partnership with French firms Corsica Sole and Mirova. The core technology involves 54 battery containers supplied by Nidec Conversion.
Construction began in mid-2024, with grid connection originally expected by Q3 2025. Full market services were projected for early 2026, but this failure during the commissioning phase raises concerns.
Technical Ambition: First 330 kV Connection
The Kiisa battery park is technically ambitious. It connects to the Estonian transmission network (Elering) via a 330 kV underground AC cable—the first of its kind in Estonia at this specific voltage level.
A major construction milestone was the delivery and installation of a massive 126-ton transformer. This equipment is critical for managing high-voltage power flows between the battery park and the national grid.
However, high-voltage integration requires precise control. As demonstrated on January 20, even minor configuration issues in such powerful inverter-based systems can cascade into grid-wide disturbances.
Elering’s Stance: A Critical “Learning Experience”
Elering, Estonia’s transmission system operator, described the event as a significant learning opportunity. This is particularly relevant as the Baltic region prepares for desynchronization from the Russian grid.
While Elering initially withheld the specific project name, they confirmed the oscillation was caused by a device connected to the main grid that failed to comply with network requirements.
Reigo Kebja, head of asset management at Elering, stated that the operator is analyzing the incident. He emphasized the need for additional measures as the number of inverter-based devices on the network grows.
“It is crucial to increase awareness among market participants about the potential effects of such incidents on the entire system,” Kebja noted.
The Blame Game: Developer Points to Supplier
Evecon CEO Karl-Joonatan Kvell confirmed in a written response to local media that the device referenced by Elering was indeed part of the Kiisa battery park.
Kvell emphasized that the fault occurred during a configuration and testing period, not during regular operations. He noted that compliance tests are designed specifically to validate the system under real-world conditions.
However, regarding accountability, Kvell placed the burden on the technology provider. He stated that primary responsibility for the incident lies with Nidec Conversion.
“The ongoing testing phase is being carried out by the system manufacturer, who remains responsible until the system’s final commissioning,” Kvell said.
