Cable explains the causes and solutions for water ingress in high and low voltage cable products!
Causes:
1: Newly purchased cable drums are sealed with plastic seals at both ends during storage. However, after a certain amount of cable is used, the remaining cable is wrapped in plastic paper and tied with string. This poor sealing allows moisture to seep into the cable over time.
2: During cable installation, the plastic-wrapped cable ends can sometimes be immersed in water, allowing water to enter the cable. During cable pulling and conduit threading, the outer sheath can sometimes rupture.
3: Failure to promptly manufacture cable ends after installation leaves unsealed cable ends exposed to air or even submerged in water for extended periods, allowing moisture to enter the cable.
4: During cable end fabrication (including terminal ends and intermediate connectors), the cable ends can sometimes slip into waterlogged cable wells due to carelessness on the part of the manufacturer.
5. When a cable is in operation and a fault such as a puncture occurs in an intermediate joint, water in the cable well can enter the cable through the gap. Water can also enter the cable at construction sites if external forces cause cable damage or puncture.
High-voltage cable solutions:
1. Seal the cable ends. Sawed-off cable ends should be sealed with plastic (using cable-specific sealing sleeves) when stacking or laying to prevent moisture ingress.
2. Fabricate cable ends promptly after laying.
3. When purchasing cable, choose a manufacturer of reliable quality. Because impurities and pores in the insulation are the starting point for water treeing, cable quality is crucial to preventing water treeing and degradation.
4. Strengthen the management of cable end manufacturing. Once water enters the cable, the cable end is often the first to experience puncture. Therefore, a well-made cable end can extend the overall life of the cable.
5. Use cold-shrink cable ends. 3M's cold-shrink silicone rubber cable accessories are simple and convenient to manufacture, requiring no blowtorch or soldering. Zhengzhou Wire and Cable
6: Long Cables Use Cable Branch Boxes. For several long cables in our bureau, each approximately 3 km in length, we use one or two cable branch boxes in addition to intermediate joints. This prevents water from spreading to other sections of the cable if one section gets flooded. This also facilitates segmental locating in the event of a cable fault.
7: PVC plastic double-wall corrugated conduit is used. This conduit is corrosion-resistant, has a smooth inner surface, and offers excellent strength and toughness. This significantly reduces damage to the cable sheath during direct burial.
8: Cable Testing: After the cable head is fabricated, a high-voltage DC leakage test is performed prior to commissioning. Subsequently, we only perform pre-tests on cables exiting the substation; other cables are not tested.
