GIC Modelling for an Overdetermined System

Geomagnetically induced currents (GIC) in power systems can cause problems ranging from overload of transformers to power blackout. Modelling can be used to show the GIC flow throughout a power system; however, the modelled GIC values have uncertainties because of the simplifying assumptions. Measurements of GIC in transformer neutral-ground connections are usually only available from a few substations. The best GIC information could be obtained by combining these measured GIC values with GIC modelling by using singular value decomposition method for an over-determined system. Model solutions for a sample power grid are presented using both the mesh impedance method and the nodal admittance method. This provides a method of how measured values of GIC can be included in the modelling process to provides better simulations of the GIC across a large network affected by a non-uniform geoelectric field.