Comparison of EPDM/SIR insulation performance and mechanism analysis of the distribution cable accessories under moisture condition

Moisture in the insulation of distribution cable accessories is one of the important causes of insulation degradation and discharge failure of the accessories. The changes in the insulation properties of ethylene-propylene-diene monomer (EPDM) and silicone rubber (SIR) with the time of dampness are studied, and the mechanism of dampness is revealed by combining the surface water absorption characteristics and functional group analysis. The results show that the hydrophobicity of EPDM specimens is lower than that of SIR, resulting in the electrical properties of EPDM being significantly lower than those of SIR after water immersion. The resistivity and the flashover voltage of both specimens decrease significantly with the increase of moisture exposure time, and the decrease of EPDM is more obvious than that of SIR. The breakdown voltage of EPDM decreases by 26.6% and that of SIR decreased by 13.06%. Besides, the flashover voltage along the surface of both EPDM and SIR decreases with the increase of water immersion time, and the decreasing trend of both of them is basically the same. This work has guiding significance for the material selection of the cable accessories and the analysis of damp failure.