Cases of Frequency Disturbance Events from SMDs

Field frequency data of three real event cases from SMD-Ls. Case 1:  a fast event.At 17:21:31 on March 18, 2020, the second-line circuit breaker in Shanan, Jibei, China tripped. The valid SMD-L data points in the AC network of North China are in place H, Z, X, and N. Case 2:  a slow event. At 12:14:46 on September 29, 2021, in the East China Power Grid, the generator cut-off experiment was started, resulting in a total power loss of 3MWs, which took 46 seconds to recover frequency above 49.95Hz. The effective SMD-L points in the East China AC network are in place J and T. Case 3:  events with both fast and slow dynamics. In 2020, on March 18, the power grid in southern Hebei encountered strong winds, resulting in large-scale wind turbine losses after reaching the cut-out wind speed. From 17:00, the southern Hebei power grid lost 700MWs of power. Multiple line trips, generation trips, and frequency oscillation events occur in succession.