A Framework for Computing Harmonic Power Flows Due to Geomagnetically Induced Currents in Power Systems

Geomagnetically Induced Currents (GICs) in power systems can cause problems in grid operations as they serve as a source of harmonics due to transformer core saturation. This results in distortion of currents and voltages thereby affecting the quality and reliability of power transfers in the system. Hence, it is important to analyze the impact of these GICs on the currents and voltages in the power system. This paper presents a framework to model and analyze the impact of GICs. First, the harmonic spectra of the currents injected by GIC-affected transformers are computed using an electromagnetic transient (EMT) program, which simulates the harmonic emissions of the transformers under the combined effect of GICs and fundamental AC excitation voltages. Then, these harmonic spectra of transformer currents are modeled in the power system using current sources and the impact of GICs are studied by computing unbalanced harmonic power flows. The end results are voltage and current distortions at every location of the power system. These results can be a foundation for performing geomagnetic disturbance (GMD) vulnerability assessment as required in NERC Standard TPL-007-4 and used for evaluating the harmonic distortion impact on protection systems and, if required, filters are designed to prevent equipment tripping during these GMD events.