An Accurate Approach to calculate the Voltage Distribution on the Transformer winding under Inter - turn short circuit Faults

The knowledge of the voltage distribution of the transformer winding is one of the important concerns, as the transformer specification and insulation coordination is based on this voltage distribution. The non-uniform voltage under transient, very fast transient and fault cases is considered as a basic cause of the breakdown of the insulation of the transformer. In this work, a methodology to determine the capacitance matrix of the transformer winding under inter-turn short circuit fault using COMSOL Multiphysics software is presented. This method guarantees accurate values of the capacitance under the fault case, as the leakage flux effects are taken into account. Then this capacitance matrix is processed using the Multi-Transmission Line Model (MTLM) to calculate the voltage distribution on the winding. The MTLM has the merit of the simulation of the very fast transients accurately. The results of this work are consistent with the results calculated in this field test in the healthy case. Moreover, this model calculates the voltage distribution on the winding under inter-turn short circuit faults.