Space weather

Space weather

Vol. 4 Issue 3

Avoiding grid disruption and transformer impact from geomagnetic disturbances

When you think of disruptive weather, snow storms, thunder storms, lightning and high speed winds probably come to mind. Solar storms can also cause problems for the electric power grid and leave millions without power with limited advanced warning. These high impact, low frequency events do not happen often, but when they do, the consequences can potentially be severe.

Space weather: What is it and why should we care?

Solar flares can create severe geomagnetic disturbances (GMDs) impacting the upper layers of the Earth’s atmosphere inducing currents in long power lines near the Earth’s surface. These quasi-dc geomagnetically-induced currents (GIC) that flow through the grounded windings of power transformers introduce a bias onto the ac sinusoidal flux in the transformer core, resulting in asymmetric or half-cycle saturation. This half-cycle saturation, as seen in the example in Figure 1, leads to [1]:

  • increased transformer exciting current and reactive power absorption;
  • power system or network voltage instability;
  • increased transformer vibration and noise level;
  • detrimental effects of harmonic currents that result from the half-cycle saturation;
  • hot spot heating of the non-current carrying metallic structures within the transformer; and
  • hot spot heating of windings due to harmonics and stray flux.
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