Simplified models of three-phase, five-limb transformer for studying GIC effects

The paper describes capabilities of a topological model of three-phase, five-limb transformer to accurately represent its response when subjected to geomagnetically induced currents. The model is validated by close agreement of the predicted values and waveforms of the currents, voltages, and reactive power with those measured in tests performed on two 400 MVA transformers connected back-to-back and to the Fingrid power network. Results demonstrate the importance of incorporating the network representation and dispel some misconceptions about the influence of the hysteretic properties of the core and tank in modeling five-limb transformers.