Investigation of Transformer Reactive Power and Temperature Increases Under DC

Transformers subjected to Geomagnetically Induced Current (GIC) exhibit increased reactive power consumption and temperature rise. Laboratory tests were conducted to identify the reactive power consumption profiles of a three-phase three-limb (3p3L) laboratory bench-scale (300 VA) transformer. The results showed a linear relationship between the conventionally measured reactive power consumed and the level of dc. A General Power Theory (GPT) for reactive power calculation considering distortions under dc exposure was also used, showing greater increase in reactive power compared to the conventional approach. Further results showed higher surface temperature increases in the windings compared to the core limbs due to increased line currents. This research is part of an extensive study of the response of 3p3L transformers to GIC, which results will assist in improving Finite Element Method (FEM) models used for GIC studies.