A Test Case for the Calculation of Geomagnetically Induced Currents

Geomagnetically induced currents (GICs) in power systems can be attributed to problems ranging from transformer overheating, misoperation of protective relays, and voltage instability. The assessment of the geomagnetic hazard to power systems requires accurate modeling of the GICs that are expected to occur. However, to date, there are no publicly available test cases to validate software programs used to compute GIC. The following paper presents a hypothetical network that can be used as a test case for validating results from GIC modeling software. The network contains many features found in real networks such as: different voltage levels, two- and three-winding transformers and autotransformers, multiple transmission lines in the same corridorn and GIC blocking devices. GIC is calculated in the network for two geoelectric field scenarios: a 1 V/km uniform Northward electric field and a 1 V/km uniform Eastward electric field. Detailed simulation results and corresponding input data are provided for each of the two scenarios. Simulation results that are provided have been validated using four independent GIC modeling programs.

I. Introduction

During geomagnetic disturbances, magnetic-field variations drive low-frequency electric currents along transmission lines and through transformer windings to ground. These geomagnetically induced currents (GICs) produce half-cycle saturation of transformers leading to harmonic generation and increased reactive power demand that can cause misoperation of protective relays and impact system stability [1]–[7].