UFLS program to ensure stable island operation

This work highlights an introduction of UFLS (Under Frequency Load Shedding) program TEPCO (The Tokyo Electric Power Company, Inc.) has applied for more than 20 years and our experiences of dynamic simulation to determine the UFLS settings. The study concluded that the island separated from main grid where load - generation imbalance is greater than 30% can be saved by our unique UFLS scheme. Coordination with UFLS settings and over-excitation protection are critical to keep secure system performance.