Geomagnetically induced currents in the Southern African electricity transmission network

This report describes the findings of the extended investigation into the existence and effects of geomagnetically induced currents (GICs) on the Southern African network. This would also apply to any other network at mid-latitude. The transmission network was modelled and the GICs calculated for major storms at various substations. Thereafter equipment was installed at two substations to monitor the performance of transformers during geomagnetic storms. The measured results were compared to calculated for verification of the modelling technique used and assumptions made. This report also describes the performance of network equipment such as transformers and reactors in the presence of GICs. Condition monitoring is used to investigate the link between degradation of these units and geomagnetic activity. The development of a preparation process and mitigational techniques are also described in the report. By combining the advanced warning process with operational procedures it could assist network operators to manage the network during a geomagnetic storm and thus reduce the probability of network perturbations and equipment damage.