A Severe Out-of-Step Event Due to Multiple Contingencies

This paper describes the complex effects of multiple contingencies which contributed to a significant out-of-step event on an actual power system. The timeline of the actual event and an impedance plot demonstrating the out-of-step condition are used to evaluate the system behavior. Contributing factors to the event's severity and deficiencies in the protection systems are analyzed and recommendations are made to improve system resiliency. Although inverter-based resources were not a significant factor in this event, lessons learned from this event are applicable to the grid of the future where IBRs are projected to be prominent and power swing rates are expected to be higher.