A Comprehensive Study of Geomagnetic Disturbance (GMD) System Impact

Published via IEEE Xplore


  • Sarina Adhikari, EnerNex
  • David Mueller, EnerNex
  • Reigh Walling, Walling Energy Systems Consulting
  • Adam J. O’Laughlin, United Illuminating Company


Quasi-dc geomagnetically induced currents (GIC) resulting from the geomagnetic disturbances (GMD) flow through the neutrals of grounded-wye transformers causing half-cycle saturation. The saturated transformers act as large reactive power sinks and also inject abnormally severe harmonic currents into the system, resulting in potential risks of system voltage collapse and equipment damage. To adequately evaluate potential system impacts of GMD, a comprehensive study that links GIC flow analysis, fundamental frequency loadflow analysis and harmonic analysis is required. The linkages between the study areas combined with the large amount of system data requires a specialized software platform. This paper describes a comprehensive evaluation of potential GMD impacts on a utility system in which a novel integration of diverse software tools was applied. Significant conclusions from the analysis are that system voltage collapse may occur at GMD intensities less than that which are likely to cause a direct risk to transformers, and harmonic impacts may be disruptive at lower GMD intensity than the threshold of voltage collapse.