PJM issued a geomagnetic disturbance warning, then an action. No emergency actions, and it's already over.

    Msg ID:     104606
    Message Type:  Geomagnetic Disturbance Action 
    Priority:     Action
    Effective Start Time:  06.01.2025 09:31
    Effective End Time:  06.01.2025 12:25
    Regions  COMED

    A Geomagnetic Disturbance Action has been issued as of 09:31 on 06.01.2025 to protect
    the power system from damage or disruptions due to increased geomagnetic activity.

Times are "Eastern Prevailing Time", which is Eastern Daylight Time right now.

Background:

These messages are from the US east coast power grid control room in Valley Forge, PA sending to people at generating stations and other key control centers. This is a slow-moving event. If the grid was stressed, there would be "Pre-Emergency Load Reduction" and "Conservative Operation" actions ordered. If there was real trouble, there would be many more actions. But things never got beyond preparing for trouble.

A geomagnetic disturbance event in 1989 caused transformer damage leading to outages. The solar flux going between power lines and conductive ground induces DC currents into the ground and lines, so that ground potential is different at different points. This causes partial saturation of transformers, and heating. That wasn't noticed until it was too late. So now, DC current in some key AC lines is monitored continuously, so power levels can be reduced if necessary.

Training materials for understanding this:[1] Start at slide 21.

Background info on how a power grid works.[2] Start with "PJM 101"

[1] https://pjm.adobeconnect.com/p63ultsdb2v/

[2] https://www.pjm.com/training/training-resources

M8.2 solar flare, Strong G4 geomagnetic storm watch