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How can geomagnetic storms damage electrical transformers?

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Space weather Earth's full North Polar auroral oval, in an image taken in ultraviolet light by the U.S. Polar spacecraft over northern Canada, April 6, 1996. In the colour-coded image, which simultaneously shows dayside and nightside auroral activity, the most intense levels of activity are red, and the lowest levels are blue. Polar, launched in February 1996, was designed to further scientists' understanding of how plasma energy contained in the solar wind interacts with Earth's magnetosphere.

Geomagnetic storms damage electrical transformers by inducing enhanced electric currents within long-distance power transmission lines.12

These storms occur when solar activity, such as coronal mass ejections, causes sharp fluctuations in Earth’s magnetic field. When the solar wind and interplanetary magnetic field couple with the geomagnetic field, they create voltage surges in long conductors, including power distribution systems.21

These induced currents can overwhelm and destroy electrical transformers, potentially triggering a cascade of power failures across large sections of an electric grid. A notable example occurred during the 1989 solar maximum, when such a storm caused a massive power outage in Quebec. Experts warn that a severe event, similar to the 1859 solar storm, could disable a significant portion of the North American power grid, leading to long-term recovery efforts and substantial economic loss.1