Analysis of Local Moisture Diffusion Coefficient of New and Aged Oil-impregnated Pressboard Based on Terahertz Technology

Moisture is an important factor affecting the electrical strength of oil-paper insulation. Effectively predicting the moisture content of each point of oil-paper insulation is an important means to assess the risk of oil-filled equipment. At present, a lot of research focuses on the exchange and diffusion of moisture at the interface between solid insulating paper and insulating oil. Due to the lack of suitable non-destructive detecting methods, there are few studies on the migration and diffusion behavior of moisture inside insulating pressboard. This paper uses terahertz technology to detect moisture quickly and non-destructively, and characterizes moisture content through the terahertz absorption coefficient of 0.3 - 1 THz. Based on the Fick model, a two-dimensional diffusion model of local moisture in pressboard is established. This method was used to study the local moisture diffusion behavior of new and aged oilimpregnated pressboard, and the diffusion coefficient was calculated. The results show that at low moisture content, the diffusion coefficient of moisture migration in aged paperboard is slightly larger than that of new paper, while at high moisture content, new paper is larger than aged paper.