Influence of Interface Moisture on Insulation Properties of Power Cables

Cross-linked polyethylene cables have been widely used in urban distribution networks. Due to the complex structure of the intermediate joint, it may get damp during operation and installation. After getting damp, the interface formed by the silicone rubber and the main insulation of the cable will have moisture intrusion. This will have an impact on the insulation resistance of the interface. To this end, this paper studies the simulation method of the intermediate joint interface, constructs a simplified model of the interface, and studies how to apply pressure to the interface. Then the insulation resistance of the interface under different pressures was measured when moisture penetrated the interface, and its change with time was observed. Research results show that when the interface is dry, the measured interface resistance is infinite. Once water penetrates the two poles, the resistance immediately drops to several megaohms; the interface pressure can inhibit the evaporation of interface water and make the insulation resistance value change more stable; pressure has a significant impact on moisture. The distribution plays an important role. When there is cotton cloth or cotton thread, the pressure will squeeze the water out of the cotton. When there is only pure water in the interface, the pressure will squeeze the water to spread around.