1. For medium-voltage XLPE insulated power cables, the following waterproofing structures are commonly used:
① For single-core cables, semi-conductive water-resistant tape is wrapped around the cable's insulation shield, conventional water-blocking tape is wrapped around the metal shield, and then an outer sheath is extruded. The outer sheath material can be standard PVC or HDPE with radial water-blocking properties, depending on other cable performance requirements. For three-core cables, to ensure adequate contact with the metal shield, semi-conductive water-resistant tape is wrapped only around the insulation shield, without water-blocking tape around the metal shield. Depending on the waterproofing requirements, the filling material can be conventional or water-blocking. The inner lining and outer sheath materials are the same as those described for single-core cables.
② A layer of aluminum-plastic composite tape is longitudinally wrapped inside the outer sheath or inner lining as a waterproof layer.
③ The HDPE outer sheath is extruded directly onto the cable.
2. For XLPE insulated cables above 110 kV, a metallic sheath is primarily used to achieve waterproofing. The most significant feature of the metal sheath is its complete impermeability, so cables with a metal sheath have excellent radial water resistance. The main types of metal sheaths include: hot-pressed aluminum sheath, hot-pressed lead sheath, welded corrugated aluminum sheath, welded corrugated steel sheath, and cold-drawn metal sheath.
