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Again, geomagnetic storms can produce an impulsive disturbance to Earth’s magnetic field over wide geographic regions.
This field disturbance causes geomagnetically induced currents or GIC, which can, depending on the ground impedances, flow through the high voltage system.
These currents can saturate transformers causing heating that can damage them.
Geomagnetic Storm Watch
When a G1 or greater geomagnetic storm is expected, SWPC will issue a Geomagnetic Storm Watch. This can be issued as much as 3 days before the storm is expected. A Warning will be issued after the CME reaches the DSCOVR spacecraft (20-50 minutes before storm onset), and an Alert goes out when the geomagnetic storm begins. These processes are already in place to distribute geomagnetic storm watches and warnings across all power grid entities in North America.
Upon receiving SWPC Watches and Warnings, grid operators will take various actions to ensure the stability of the grid. Activities include, but are not limited to:
- Discontinue maintenance work and restore out-of-service transmission lines
- Avoid taking transmission lines out of service
- Increase real and reactive reserves to preserve system integrity
- Reduce generator loading to provide reserve power and reactive capacity
Weather on Earth obviously affects the electric utilities. Heat waves, ice storms, hurricanes, etc., put considerable stress on the grid. Grid operators will closely monitor weather influences on their systems when geomagnetic activity is expected.