System-Wide Case Study Assessment of Transformer Heating Due to Geomagnetic Disturbances

The geomagnetically induced currents (GICs) are a potentially catastrophic threat to large-scale power system operations especially the bulk transformers, possibly leading to severe outages. This paper provides a system-wide transformer temperature analysis due to GIC-induced half-cycle saturation. The derived thermal assessment model identifies the potential overheated transformers in a geomagnetic disturbance (GMD) event and characterizes the relationship between the GIC and the transformer's temperature response. The suggested approach is applied to the 20-bus GIC benchmark test case facing a GMD event, where the time-varying temperature responses are evaluated and numerically analyzed in both normal and hotspot contingency scenarios.