Calculation of Inrush Currents – Benchmarking of Transformer Models

The paper investigates the behavior of four transformer models in electromagnetic transients programs (EMTP) when calculating inrush currents due to shell-type transformers energization. These models are single-phase Saturable Transformer (STC), BCTRAN, Hybrid Transformer (XFMR) and UMEC. The measurements of a real transformer energization performed by EDF in France are used to evaluate the accuracy of the simulation results provided by each model. For the first periods of the inrush, the results show that only a topologically correct transformer model as the hybrid transformer model is able to reproduce the current amplitude in the three phases and the overall wave shape. BCTRAN, STC and UMEC may predict the first inrush current peak, but the amplitudes in the other two phases are far from the measurements. The current decay in the 2 seconds after the energization is poorly predicted by all of the models underlining a poor losses representation in the transformer model and in the rest of the network.