Geomagnetically Induced Current Effects on Power Systems

Geomagnetically induced currents (GICs) arise when rapid variations in the Earth’s magnetic field, driven by solar storms and substorms, induce electric fields in the ground. These surface electric fields can enter high-voltage power networks through transformer neutrals and earthing systems, producing quasi-dc currents that flow alongside normal alternating currents. In exposed regions, particularly at high and mid latitudes, large GICs can drive transformers into half-cycle saturation, generate harmonic distortion, increase reactive power losses and, in extreme cases, precipitate cascading equipment failures and widespread blackouts. The magnitude of GICs depends on the spatiotemporal characteristics of the geomagnetic disturbance, the three-dimensional conductivity structure of the subsurface and the topology and earthing configuration of the transmission network.

Modelling approaches combine geomagnetic field observations or forecasts with ground conductivity models, using techniques such as the thin-sheet approximation or three-dimensional volume-conductor simulations, to estimate surface electric fields. These fields are then coupled to detailed network models—employing nodal admittance matrices or equivalent methods—to simulate GIC flow and assess vulnerability at individual substations. Recent advances emphasise real-time monitoring platforms, improved global conductivity maps and integrated warning systems to support grid operators in adopting mitigation strategies, such as series capacitors, neutral blocking devices and operational procedures during severe space-weather events.

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Geomagnetically Induced Current Effects on Power Systems publication trend

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Technical terms

Geomagnetically Induced Current (GIC): Quasi-dc currents driven through grounded electrical networks in response to geoelectric fields induced by geomagnetic variations.

Geoelectric Field: Electric field at the Earth’s surface generated by time-varying magnetic fields during space-weather events.

Thin-Sheet Approximation: Two-dimensional model treating lateral conductivity contrasts at the surface as a sheet to calculate induced electric fields efficiently.

Nodal Admittance Matrix: Mathematical representation of a network’s conductance used to compute currents and voltages when driven by external sources.

Transformer Saturation: Condition in which a transformer core is driven beyond its linear magnetic response, leading to harmonics and overheating.

References

1. Geomagnetically induced currents: Science, engineering, and applications readiness. Space Weather (2017).
2. The Role of Global/Regional Earth Conductivity Models in Natural Geomagnetic Hazard Mitigation. Surveys in Geophysics (2019).
3. Comparison of methods for modelling geomagnetically induced currents. Annales Geophysicae (2014).
4. Geomagnetically induced currents in the Irish power network during geomagnetic storms. Space Weather (2016).
5. Long‐Lasting Geomagnetically Induced Currents and Harmonic Distortion Observed in New Zealand During the 7–8 September 2017 Disturbed Period. Space Weather (2018).