Improved Transformer Duality Model for Geomagnetically Induced Currents

Abstract: A lumped element transformer tank model has been developed for evaluating the power dis-sipation in the tank and flux distribution in the transformer when it is subjected to a DC current in the neutral. FEM simulations are performed to assist in developing a per-phase magnetically separated transformer tank model that takes into account currents induced in the tank. The tank is modeled with a reluctance network that is transformed to its electrical equiv- alent using the duality principle. The electrical equivalent lumped element transformer models are simulated using circuit simulation software. The models are subjected to a DC current in the neutral in the circuit simulation software. For the T-core transformer the tank is saturated at comparably low DC currents in the neutral. The power dissipation in the tank for DC currents in the neutral is found to be low compared to other loss components. However, the proposed per-phase models show a higher power dissipation in the tank compared to the zero-sequence tank model. Lumped element modeling provides an efficient alternative to FEM simulations for simu- lating the electromagnetic behavior of the power transformer when subjected to DC currentsin the neutral.