Transformer inrush
When transformer is energized, winding currents could become substantially large to cause relay misoperation. Several factors could impact magnitude of the inrush current like the switching timing, source impedance, remnant flux, etc.Transformer core has nonlinear characteristic (can be modeled as magnetizing branch). When it comes to modeling, BH curve that describes the magnetic material is normally not handy. A transformer is normally designed to ensure that the magnetic flux density is below the level that would cause saturation [1] [2].
The excitation v-i curve is usually available in the test report. If ATP-EMTP is used, SATURA program can be used to generate current-flux curve from the v-i curve. The output will be stored in a .pch file. Furthermore, to get the hysteresis characteristic [3] another HYSDAT routine could be used to generate the current-flux pair given a saturation point. These data points can then be input of the nonlinear component in ATP [4] [5] [6] which would form the nonlinear branch of the transformer.
Below are some inrush currents (HV winding and magnetizing branch) captured in a simple test system I modeled during transformer energization in ATP. Further analysis or studies on the currents or energization process could be carried out.
[1]https://www.voltech.com/support/technical-articles/transformer-basics/
[2]https://www.mathworks.com/help/physmod/sps/ug/custom-transformer-b-h-curve.html