Magnetic flux leakage, eddy current loss and temperature distribution for large scale winding in UHVDC converter transformer based on equivalent 2D axisymmetric model

Temperature distribution is an important index that reflects the safe operation ability of power transformers. In this paper, finite element simulation is used to study the magnetic field, loss, and temperature distribution of an ultra-high voltage converter transformer. Firstly, the magnetic reluctance equivalent method was proposed to establish a 2D axisymmetric model, and the frequency domain solution was achieved based on the magnetic energy equivalent method. The results demonstrate that this method reduces solving time by 10 times compared to traditional method, and the simulation results are consistent with measured short-circuit impedance, indicating the effectiveness and efficiency of this method. Secondly, the magnetic flux, loss, and temperature distribution of the winding were studied. It was found that eddy currents have a significant impact on the losses at the end and outer diameter of the winding, leading to uneven winding temperature distribution. The hot spot temperature with eddy current loss is 14.3 K higher than that without eddy current loss, and the hot spot temperature is 27.8 K higher than the average temperature, which is significantly different from AC transformers. This study has positive significance for the safe and reliable operation of converter transformers.