In urban power grid reconstruction projects, power cables have been widely used. However, due to the special nature of cables, there are special requirements for their installation, operation and maintenance. Cable moisture or water ingress reduces the insulation resistance of cables, which is one of the important factors that cause cable line operation accidents. Causes and hazards of cable moisture and water ingress (1) When a new cable is shipped from the factory, both ends are sealed with plastic sealing sleeves. However, after a section is used at the construction site according to the actual situation, the remaining part is simply wrapped with plastic sheeting. Since it is usually placed in the open air and the sealing is not good, it is inevitable that water vapor will penetrate into the cable over time. (2) When laying cables, they often need to cross roads, bridges and culverts. Due to weather or other reasons, a lot of water often accumulates in the cable trench. During the laying process, it is inevitable that the cable head will be immersed in water. Water will enter the cable due to the loose or damaged plastic sheeting. In addition, when pulling and threading the pipe, the outer sheath or even the steel armor may be scratched. This phenomenon is particularly prominent when mechanical traction is used. (3) After the cable is laid, the cable head cannot be made in time due to the limitation of on-site construction conditions, so that the unsealed cable end is exposed to the air for a long time, or even immersed in water, allowing a large amount of water vapor to enter the cable. (4) During the cable head production process, due to human negligence, water may seep into the cable end during the processing. (5) During the normal operation of the cable, if a breakdown or other fault occurs for some reason, the accumulated water in the cable trench will enter the cable along the fault point; in civil construction, especially in construction sites using large construction machinery, cable damage or breakdown accidents caused by various human factors are also common. When such accidents occur, the cable insulation is severely damaged, and water may also enter the cable. What should be done after the cable is wet? 1. Make the cable head in time after the cable is laid and complete the wiring to eliminate the hidden dangers in the bud. 2. If only the two ends of the cable are flooded, just cut off the two ends and re-wire the cable head. 3. If there are obvious water ingress points on the cable, cut the cable near the ingress point and make intermediate joints.
4. Water accumulation is inevitable in outdoor cable wells or cable ducts. Try to secure the cables with brackets.
5. Use specialized hot nitrogen to pressurize and dry the cable interior; such specialized equipment is generally unavailable.
6. Regularly perform pressure and leakage tests on the cables to ensure timely monitoring of their operating status.
The best way to prevent water ingress is prevention. Once a cable becomes severely damp, it is essentially useless. Therefore, choosing high-quality cables early on can reduce the risk of moisture. In addition to choosing high-quality cables, routine inspection and maintenance are also crucial. After all, eliminating potential faults ensures proper cable operation and prevents further serious incidents. This ensures the safe and stable operation of the power distribution network.
