and planning standpoint, we are probably looking at a minimum of, say, 3 to 4 hours in advance, where we can make a tactical decision and still feel confident in the operation.”
A geomagnetic storm that occurred in 1989 caused a blackout in the Quebec province of Canada (Figure 5.4). A transient disturbance of Earth’s magnetic field, a geomagnetic storm is caused by energetic streams of particles and fields that originate from the Sun and impact and distort Earth’s magnetic field. The transient changes in Earth’s magnetic field interact with the long wires of the power grid, causing electrical currents to flow in the grid. The grid is designed to handle AC currents effectively, but not the DC currents induced by a geomagnetic storm. These currents, called geomagnetically induced currents (GICs; also known as ground-induced currents), cause imbalances in electrical equipment, reducing its performance and leading to dangerous overheating. A major electrical transformer was damaged in the 1989 Quebec event (see Figure 5.4), resulting in significant direct financial loss to the utility in addition to other indirect losses to the northeastern U.S. and Canadian economies from the blackout. Procedures were adopted, and are currently in place, that inform electric grid operators to take actions that will prevent a blackout and to protect equipment.