The conservative insulation thickness design increases the production cost of the cable, while the increase in thickness leads to a reduction in the electrical properties of the insulation material. Therefore, the study of thickness effect of insulation breakdown field strength of high-voltage DC cables has practical engineering significance. In this paper, we selected Nordic Chemical 220 kV high-voltage AC XLPE insulation materials and studied the effect of thickness on the electrical and mechanical properties of XLPE insulation materials by conducting AC breakdown experiments, conductivity tests and mechanical property tests on different thicknesses of the styles. The results show that: the AC breakdown field strength of XLPE decreases with increasing thickness, and the breakdown field strength of XLPE at 30 microns increases by 189.6% compared with that of XLPE at 300 microns; the DC conductivity of XLPE increases with increasing thickness of the samples, and the conductivity of XLPE samples also increases with increasing temperature. The thickness has an effect on the mechanical tensile properties of XLPE. The elongation at break of XLPE samples increases with the increase of thickness, and the XLPE breaking strength also increases with the increase of thickness. The experimental results indicate that both electrical and mechanical properties of XLPE insulation are affected by material thickness, which provides experimental support for the thickness design of XLPE insulated cables.

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