Checking the PJM power grid's alerts: Warning: A Geomagnetic Disturbance Warning has been issued for 01:47 on 09.08.2017 through 17:00 on 09.08.2017 . A GMD warning of K7 or greater is in effect for this period. Additional Comments: SpaceWeatherPredictionCenter Extended original Warning of GMD Intensity of K7 or greater until 9/8/17 21:00 UTC (17:00 EDT). Warning: A Geomagnetic Disturbance Warning has been issued for…
My understanding is that the vast majority of power infrastructure is AC, and long distances are using High Voltage AC lines