Geomagnetic Disturbances

Geomagnetic disturbances (GMD) occur when solar storms on the sun’s surface send electrically charged particles toward earth, where they interact with earth’s magnetic field. This interaction potentially has implications for the nation’s high-voltage transmission grid. GMD can send geomagnetically induced currents (GIC) through transmission lines, potentially through transformers and into the earth through ground connections.

If the intensity and duration of a disturbance is sufficient, these abnormal electric currents may reduce system voltage and in the worst case, cause a widespread power outage. In the extreme, severe GIC can overheat transformer cores and lead to equipment damage or failure.

Solar storms typically occur in 11-year cycles. Solar Cycle 24 began in 2008 and the solar storm frequency during this cycle is expected to peak in 2013. During more than a century of operation, American Electric Power’s (AEP) system has experienced numerous geomagnetic disturbances. In that time some temporary effects have been observed, but there has been no lasting damage or consequences. AEP is less susceptible than utilities closer to the earth’s magnetic poles or in areas with more rocky soils.

AEP Transmission's GMD Preparations

AEP mounted GIC monitors on power transformers during two previous cycles and detected GIC, but there was no evidence of lasting adverse impact. In anticipation of Solar Cycle 24, AEP Transmission has taken steps to learn more about the phenomenon and proactively taken precautions by:

  • addressing GIC risks in new transformer specifications;
  • studying the AEP system to identify potential GIC vulnerability;
  • installing monitors to evaluate GMD impact at multiple locations;
  • participating in the evaluation of GMD "blocking" equipment;
  • evaluating the risks and remedies for satellite communication disruptions;
  • updating operating procedures to mitigate risks; and
  • collaborating with the Electric Power Research Institute (EPRI), the North American Electric Reliability Corporation (NERC) and the Department of Energy (DOE) to share knowledge, insights and evaluate equipment and methods to mitigate GMD.

Additionally, AEP has business continuity plans in place to sustain essential operations, 24/7 Transmission Operations Centers with back-up power sources on-site and regularly conducts drills of the AEP System Restoration Plan to enable resumption of normal operations, should an abnormal condition occur.

Geomagnetic Disturbance Q&A

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