Study of power transformer excitation under GIC

This paper describes transformer excitation under the influence of geomagnetically induced currents (GIG). An equivalent magnetic circuit model based on 3D finite element magnetic flux distribution analysis was developed to replace the constant magnetizing inductance of the conventional equivalent Tee circuit. The modified nonlinear equivalent circuit is capable of simulating transformer performance under a wide range of GIC levels. Using a single phase transformer example, the effect of each lumped component in the Tee circuit (leakage inductances, winding resistances, core loss resistance) on the excitation current is studied in detail