> First, the intense magnetic field variations in the magnetosphere induce electric fields and currents over large areas of Earth's surface. In turn, this geoelectric field creates what are known as geomagnetically induced currents, or GICs, which flow in any available conductor, including high-voltage transmission lines, oil and gas pipelines, railways, and undersea communications cables. These interconnecting networks essentially act as giant antennas that channel the induced currents from the ground. Hit with a 300-ampere GIC, a high-voltage transformer's paper tape insulation will burn, its copper winding will melt, and the transformer will fail, either right then and there or in the future.
> There is a quick and relatively cheap fix to help protect these transformers from geomagnetically induced currents: They can be retrofitted to block the inflow of GICs. But no utilities anywhere routinely protect their multimillion-dollar transformers in this way.
Well, if both the transformers and actual long distance wires survive the event, then the grid can be brought back up.
Most of grid 'defenses' involve some temporary disconnection of components; the robustness question is how quickly you can reconnect again - is it an automatic switch after half a second, or does it require sending repair squads to thousand remote locations.
> There is a quick and relatively cheap fix to help protect these transformers from geomagnetically induced currents: They can be retrofitted to block the inflow of GICs. But no utilities anywhere routinely protect their multimillion-dollar transformers in this way.