Correlation of Macroscopic Interface Breakdown Characteristics and Microscopic Particle Motions at the XLPE-SiR Insulation Interface of Cable Joints

This paper explores the correlation between the macroscopic breakdown behavior and microscopic particle motion of cable joint cross-linked polyethylene–silicone rubber (XLPE-SiR) insulation interface breakdown. Firstly, based on the characteristics of Pd values exceeding 1000 Torr·cm at the insulation interface, it shows that XLPE-SiR insulation interface breakdown falls within the scope of streamer discharge. Further, the generation process of the insulation interface breakdown is described through microscopic particle motions, and the microscopic expression of the interface breakdown energy of cable joints is derived. Based on this, it is found that the ionization degree (χ) of the interface breakdown channel is the major microscopic parameter that affects the interface breakdown energy. An experiment was conducted on equivalent samples under different conditions of pyrolysis degree interface pressure (P) and breakdown gap (d). The experiment shows that the value of χ is positively related to the pyrolysis degree and P. Additionally, it is found that with the increase in d, the value of χ increases at first and then decreases gradually. The results of this paper can be taken as a basis for research on the microscopic process of XLPE-SiR insulation interface breakdown at different stages.