Impact of Time-Dependent Transformer Thermal Model on Assessment of GICs in Large Power Systems

Geomagnetically induced currents (GICs) in power systems are a potential source of introducing DC in transformers, resulting in undesirable occurrences of additional harmonics and higher temperatures. This paper reviews the methodology and results of case study that was performed on the transformer fleet of a 2000-bus synthetic grid on the geographic foot-print of Texas. The thermal assessment technique identifies the transformers with potential thermal impacts using a first-order hotspot calculation method for the structural parts of the power transformer. The analysis is undertaken by modeling severe GMD events-NERC benchmark event and its derivatives—to assess how the transient hotspot behavior of a power transformer is related to various environmental conditions, such as electric field magnitude and direction, transformer neutral current, and storm duration.