The oil flow distribution and winding temperature rise of utral high voltage(UHV) converter transformers are crucial for optimizing design margin and enhancing operational reliability. For UHV converter transformers with oil-directed air-forced cooling method

the influence law of the hole parameters of the oil guide box on the oil flow distribution and winding temperature rise is still unclear. There is a lack of clear theoretical guidance in engineering design. In this paper

the computational fluid dynamics (CFD) method is employed to analyze the oil flow resistance and flow distribution within different windings. The temperature-rise distribution characteristics inside the windings are investigated

and the effects of the hole diameter and the number of holes in the oil guide box on the oil flow temperature rise are further explored. The research results show that the flow distribution within different windings is dominated by the flow resistance inside the windings. The maximum error between the simulation data and the experimental data is less than 3 K

which verifies the accuracy and reliability of the simulation model and method. The temperature rise of grid-side and valve-side windings shows a periodic spiral upward trend as the axial height increases. The diameter and the number of oil inlet holes on the grid side (valve side) mainly affect the average temperature rise and the hot-spot temperature rise of the windings on the same side

and have a negligible impact on the temperature rise of the windings on the other side. By appropriately reducing the number of oil outlet holes or decreasing the hole diameter

the temperature rise of the grid-side and valve-side windings can be significantly reduced. The research results can provide a technical support for optimizing the oil flow distribution within the windings and regulating the winding temperature rise.