Analysis of Power Transformers under Geomagnetically Induced Currents

This paper describes the development of a low-frequency model to analyze impacts of Geomagnetically Induced Currents (GIC) on power transformers. GIC causes power transformer core and tank saturation which can conduce to flow of harmonic currents, voltage-control problems, and heating of the transformer internal components, ultimately leading to possible damages and gas relay alarm/operation. To analyze the transformer, first, an accurate low-frequency transient model is developed to allow the flow of GIC in the power transformer windings. The developed transformer transient model is based on the topological representation of the transformer core, flux air paths, and tank and is accurate enough for considering low and mid-frequency transients including GIC. The calculated currents are fed into a Finite Element Model of the transformer developed for the purpose of GIC study in this research work. Utilizing the FEM model, the pattern of electromagnetic flux distribution and hot spots caused by GIC in the transformer core and tank are specified. The extracted characteristic features of the transformer will provide helpful insights into the optimal design and production of power transformers.