During the switching of the on-load tap changer (OLTC) of the transformer, an arc is generated which causes insulating oil to vaporize and decompose, resulting in a surge of insulating oil inside the OLTC tank. As the capacity of transformer increases, the oil surge is very severe due to the large arc current during the switching process, which leads to frequent gas protection misoperations. Therefore, it is necessary to analyze the flow field during the OLTC switching process. Based on the physical process of OLTC switching, the switching process is divided into two stages for mathematical modeling, namely the bubble expansion stage and the gas-liquid two-phase flow stage. Finally, using the Comsol Multiphysics software for modeling and simulation, and the oil flow characteristics of the two stages in the connecting pipe of oil conservator were analyzed.

transformer, on-load tap changer, two-phase flow,flow field,bubble expansion