Date of Award

5-2026

Degree Name

Master of Science

Department

Electrical and Computer Engineering

First Advisor

Pablo Gomez, Ph.D.

Second Advisor

Johnson Asumadu, Ph.D.

Third Advisor

Damon Miller, Ph.D.

Access Setting

Masters Thesis-Open Access

Abstract

Geomagnetically induced currents (GICs) pose a significant threat to modern power transformers connected to long high-voltage transmission systems, particularly in regions with low subsurface electrical conductivity. During geomagnetic disturbances (GMDs), time-varying magnetic fields induce surface electric fields that drive quasi-DC currents through grounded transformer neutrals. These currents can bias transformer cores, leading to saturation, waveform distortion, and potential system instability. Despite extensive research, the role of regional Earth conductivity in shaping electric fields and transformer response remains an area requiring deeper investigation.

This study analyzes how contrasting Earth conductivity profiles influence GIC magnitude and transformer saturation risk using two representative one-dimensional soil models: the Pacific Border Province (PB-2) and the Columbia Plateau (CO-1). Time-dependent magnetic field data from the October 29, 2003, and May 11, 2024 GMD events were applied in COMSOL Multiphysics to compute electric fields, induced voltages, and transformer winding currents.

Results show that the PB-2 profile consistently produces stronger surface electric fields than the CO-1 model due to its lower conductivity, leading to higher induced voltages and larger currents entering the transformer windings. For both the 2003 and 2024 GMD events, the PB-2 model produces over 30% higher electric field magnitudes than the CO-1 model. A similar trend is observed in the GIC response, where the PB-2 model produces approximately 35% and 25% higher currents for the 2003 and 2024 events, respectively. When compared to transformer rated currents, peak GIC currents for the 2003 event reached approximately 9.3% and 6.3% of the rated primary current, and 51.6% and 21.2% of the rated secondary current for the PB-2 and CO-1 models, respectively. Similar trends were observed for the 2024 event.

The findings highlight the critical importance of incorporating geoelectric structure into GIC hazard assessment and transformer modeling practices. The integrated time-domain framework developed in this study provides a physically consistent and practical approach for evaluating transformer susceptibility to GICs and can support more informed mitigation strategies, planning decisions, and system protection enhancements.

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