| Abstract:Meta-aramid insulation paper possesses excellent heat resistance and electrical insulation properties, offering potential applications in traction transformers and high-temperature insulation systems, and the adequacy of its oil impregnation directly affects the reliability of oil-paper composite insulation structures. In this study, three typical industrial-grade meta-aramid insulating papers (basis weight 40.7-47 g/m²) were selected as test specimens for dynamic oil impregnation testing. Using Micro-CT 3D imaging combined with image preprocessing and a local threshold segmentation method based on grayscale analysis, accurate identification of fibers and pores was achieved. This enabled the reconstruction of the 3D pore structure and the extraction of parameters such as porosity, pore size distribution, average coordination number, and fractal dimension. Furthermore, pore-scale seepage simulations were employed to calculate the absolute permeability in different directions. These findings reveal the mechanism by which the three-dimensional pore structure of meta-aramid insulating paper regulates oil-impregnation behavior, providing a basis for the design of pore structures, optimization of oil-impregnation processes, and material selection for aramid insulating paper used in oil-immersed high-voltage electrical equipment. |