Changing pattern of cross-linking by-products content in XLPE insulation under different degassing temperatures

Abstract In order to study the change pattern of crosslinking by-products content inside XLPE insulation under different degassing temperatures, this paper simulated degassing tests on 110 kV XLPE insulated cables at 50 °C and 65 °C and compared them with the real degassing results of the cable factory. The results show that, the diffusion of cross-linking by-products from inside to outside and the decomposition of dicumyl peroxide (DCP) occur in XLPE under the conditions of degassing at 50 °C and 65 °C. The residual rate of cross-linking by-products is lower at 65 °C. After 84 h of degassing, the decomposition of α-cumyl alcohol into α-methylstyrene is further increased, which leads to an increase in the content of α-methylstyrene. At the same time, the diffusion rate of cross-linking by-products content in the insulation gradually increased from in-side to outside, and the reduction of cross-linking by-products is greater in the inner layer than in the outer layer, which in turn is greater than in the middle layer. Overall, for 110 kV XLPE insulated cables, it is recommended to degas at 65 °C for 7.3 days to get rid of gas. When the sum of the crosslinking by-products content in the inner, middle and outer layers of the insulation is similar, it can be considered that the diffusion of crosslinking by-products inside the insulation has reached the equilibrium.