When magnetic fields move about in the vicinity of a conductor such as a wire, a geomagnetically induced current is produced in the conductor. This happens on a grand scale during geomagnetic storms (the same mechanism also influences telephone and telegraph lines, see above) on all long transmission lines. Long transmission lines (many kilometers in length) are thus subject to damage by this effect. Notably, this chiefly includes operators in China, North America, and Australia, especially in more modern high-voltage, low-resistance lines. The European grid consists mainly of shorter transmission cables, which are less vulnerable to damage.[22][23]

The (nearly direct) currents induced in these lines from geomagnetic storms are harmful to electrical transmission equipment, especially generators and transformers — inducing core saturation, constraining their performance (as well as tripping various safety devices), and causing coils and cores to heat up. This heat can disable or destroy them, even inducing a chain reaction that can overload and blow transformers throughout a system.[24][25][26] This is precisely what happened on March 13, 1989: in Québec, as well as across parts of the northeastern U.S., the electrical supply was cut off to over 6 million people for 9 hours due to a huge geomagnetic storm. Some areas of Sweden were similarly affected.

According to a study by Metatech corporation, a storm with a strength comparative to that of 1921 would destroy more than 300 transformers and leave over 130 million people without power, with a cost totaling several trillion dollars.[27] A massive solar flare could knock out electric power for months.[28]

By receiving geomagnetic storm alerts and warnings (e.g. by the Space Weather prediction Center; via Space Weather satellites as SOHO or ACE), power companies can minimize damage to power transmission equipment, by momentarily disconnecting transformers or by inducing temporary blackouts. Preventative measures also exist, including preventing the inflow of GICs into the grid through the neutral-to-ground connection.[22]