Effect of Friction Force on Thermal Shrinkage of XLPE Insulation in Small-Specification Fire-Resistant Cables

To solve the problem of thermal shrinkage instability of cross-linked polyethylene (XLPE) insulation layer in small-specification fire-resistant cables of up to 6 mm², experiments were designed based on the thermal shrinkage mechanism and the factors affecting friction force. The effects of contact surface material and wrapping process on insulation thermal shrinkage were investigated. The experimental results showed that with increasing surface roughness of mica tape, both the contact area between the insulation layer and the mica tape and the friction force increase. In addition, wrapping the outer polyethylene terephthalate (PET) of the mica tape with the film facing outward could significantly increase the friction force. Finally, it is verified that the XLPE insulation layer with even wrapping exhibits a markedly reduced thermal shrinkage rate. This study provides a theoretical basis and engineering reference for improving the thermal shrinkage stability of insulation in small fire-resistant cables.