Analysis of the Large Disturbance in Georgian Power System: Stability Challenges and Lessons Learnt

Wide Area Monitoring System (WAMS) recordings were used for detailed root-cause analysis, revealing sustained low-frequency oscillations at approximately 0.5 Hz with progressively increasing amplitude. The primary cause was identified as incorrect operation of the hydro power plants' frequency and voltage controls, which failed to provide adequate voltage and frequency response, thereby introducing negative damping into the system. Protection schemes operated as designed but were unable to arrest the control-induced instability. Block-wise corrective actions triggered frequency overshoots and generation disconnections, accelerating inertia loss. The system collapsed within around six minutes, resulting in 1.05 GWh of unsupplied electricity. The Georgian State Electrosystem, as the Transmission System

Operator, responded rapidly to restore supply to critical consumers within 35 minutes and achieved full system recovery in 2 hours 38 minutes.

As our society becomes more dependent on electricity, ensuring a stable and reliable power supply is of high importance. This growing reliance places considerable responsibility on system operators to maintain supply security. Power systems are highly complex, large-scale networks, and despite advanced monitoring and control techniques, certain disturbance events cannot always be prevented. These events can cause widespread blackouts with significant social and financial impacts, including unsupplied energy costs, economic losses from interrupted business and industrial activities, infrastructure damage, and various opportunity costs. While it is not always possible to predict and prevent every disturbance, careful analysis of these events is essential for improving system reliability and resilience.

This paper provides a comprehensive case study of the Georgian power system blackout, analysing the event sequence, contributing factors, and subsequent restoration efforts. The study identifies critical lessons regarding the importance of coordinated frequency and voltage control, generator control integrity, proper maintenance practices, and flexible ancillary services in low-inertia systems. Key findings emphasize the need for enhanced digitalization and disciplined operational practices to mitigate high-consequence events in modern power systems. By sharing this real-world experience, the study aims to inform ongoing efforts to enhance power system technical performance and reliability across the industry.