PJM (the US east coast power grid) has issued a warning:
104202 Warning
Geomagnetic Disturbance Warning
05.10.2024 13:48
PJM-RTO
A Geomagnetic Disturbance Warning has been issued for 13:48 on 05.10.2024
through 21:00 on 05.10.2024. A GMD warning of K8 or greater is in effect
for this period.
Times are US EDT.
This is a warning only. No actions are listed yet.
' A Geomagnetic Disturbance Action has been issued as of 22:15 on 05.10.2024 to protect the power system from damage or disruptions due to increased geomagnetic activity.'
PJM has a plan. Geo-Magnetic Disturbance (GMD) Operating Plan (EOP-010-1)[1]
Usage of some specific transmission lines has to be kept below certain values.
Right now, this is a low-load period late at night without bad weather,
so there are no additional actions ordered. The system load is probably within the more restrictive limits just because it's late night. If problems develop, you'll see more actions in there. Watch morning load take-up tomorrow.
There's a press release, too.[2]
If you really want to understand this, start at page 32 of this training PowerPoint.[3] In 1989, PJM had a blackout because of this, and that's thoroughly discussed in the training materials. Geography matters. PJM has transmission lines running in the same direction as a mountain range with igneous rock. So "ground" isn't as conductive as is desirable. During a geomagnetic disturbance event, ground voltage at different points can differ. This causes problems with wye-wound transformers grounded at the center of the wye.
They get some induced DC current, which can partially saturate the magnetics and heat up transformers.
There's a control room running this in Valley Forge, PA. (And a second control room in an undisclosed location.)
(Incidentally, this has absolutely nothing to do with electromagnetic pulse problems. EMP has a rise time of nanoseconds. GMD has a rise time in minutes. Unless you have a really long wire (many kilometers) with a potential to ground, this doesn't affect much.)
Weather has been good today in the region - low heating and cooling load, and it's a weekend; demand is comfortably low (currently about 72.5GW with a forecasted peak of 77, vs an actual peak of 85GW yesterday). Should keep things pretty boring across PJM.
It's a good thing this didn't happen in July/August.
(For folks around here, the pjm now app is a nice way to grab current power demand/tie flows/alerts)
PJM ended the GMD action at 05.11.2024 12:00 EDT. The PJM manual says that GMD actions are ended after three hours with no problems.
There were no additional actions required to deal with the problem. They'd show in that list as "Conservative operations", "Pre-emergency load management reduction action", "Curtailment of non-essential building load", or even "Emergency load dump action".
K-index is at 8.67 right now, down from 9. (9 is currently the maximum reportable K value.)
This is a warning only. No actions are listed yet.