Analyzing the Effect of the Gannon Storm on the North American Electric Grid

Multiple coronal mass ejections (CMEs) collided with earth’s magnetosphere on May 10 - 12, 2024, resulting in the largest geomagnetic disturbance (GMD) in over two decades (the Gannon Storm). Bulk power system (BPS) operators received early notification from the U.S. National Oceanic and Atmospheric Administration (NOAA) Space Weather Prediction Center (SWPC) through existing protocols and Reliability Coordinators (RCs), Transmission Operators (TOPs) and other registered entities implemented GMD Operating Procedures. The BPS remained stable throughout the event as GMD conditions varied between Strong (G3) and Extreme (G5) over the three-day period. Operators observed isolated impacts to BPS transformers, voltage support equipment, transmission line breakers, and harmonic filters. Additionally, high levels of geomagnetically-induced currents (GIC) and harmonics were reported by operators and the Electric Power Research Institute (EPRI) SUNBURST monitoring network. This major storm provides an important opportunity to deepen understanding of GMD events and their effects on the BPS and continue the industry and NERC’s activities to reduce the risk that extreme GMD events pose to grid reliability. NERC, EPRI, and the electric power industry are using NERC’s data collection programs, which include the GMD Data System and various equipment data systems, to complement industry observations and insights and provide expanded understanding of the Gannon Storm's effect on the North American electric grid. The results of this review will serve to inform industry operating procedures and practices and technical guidelines used for planning and operating the BPS. Results may also support better understanding of GMD events and their impacts to electricity infrastructure by the broader space weather community.