The experience from recent space weather events suggests a threatening outcome for today’s infrastructure from historically large storms that are yet to occur.
Recent analysis by Metatech estimates that more than 300 large EHV transformers would be exposed to levels of GIC sufficiently high to place these units at risk of failure or permanent damage requiring replacement. Figure 7.2 shows an estimate of percent loss of EHV transformer capacity by state for a 4800 nT/min threat environment such as might occur during a storm of the magnitude of the May 1921 event. Such large-scale damage would likely lead to prolonged restoration and long-term shortages of supply to the affected regions.
In summary, present U.S. grid operational procedures are based largely on limited experience, generally do not reduce GIC flows, and are unlikely to be adequate for historically large disturbance events. Historically large storms have a potential to cause power grid blackouts and transformer damage of unprecedented proportions, long-term blackouts, and lengthy restoration times, and chronic shortages for multiple years are possible. As Kappenman summed up, “An event that could incapacitate the network for a long time could be one of the largest natural disasters that we could face.”
Given the potentially enormous implications of power system threats due to space weather, major emphasis focuses on preventing storm-related catastrophic failure. Trends have been in place for several decades that have