  Geomagnetic storms occurring due to sustained, high-speed solar winds are
known to induce currents in power distribution networks. These geomagnetically
induced currents (GICs) can cause high voltage transformers (HVT) to overheat,
thus resulting in a catastrophic electricity loss event (CELE). Since
significant portions of infrastructures around the world rely heavily on access
to electric power, it is essential to estimate the risks associated with GICs
on a global scale. We assemble multiple methodologies across various scientific
disciplines to develop a framework assessing the probability of a severe
geomagnetic storm causing a long-term, widespread power outage. Our model
incorporates thermal models of HVT tie bar hot spots, historical geoelectric
field estimates, and a global conductivity model to estimate the risk of
long-term power outage for regions between -70 degrees and 80 degrees
geomagnetic latitude due to transformer overheating failure. Assuming a uniform
33% HVT spare capacity, our analysis indicates that a 1 in 10,000 year storm
would result in approximately 1% of the population in Europe and North America
experiencing a long-term (months to years) electricity loss.
