1. When laying cables, it is necessary to frequently crossroads, bridges, culverts, etc. Due to weather or other reasons, water is often accumulated in the cable trenches. During the laying process, it is inevitable that the head of the cable is immersed in the water, and the water enters the cable because the plastic cloth is not tightly wrapped or damaged; In addition, when the traction and the pipe are worn, the outer sheath or even the steel shovel is sometimes scratched, which is particularly prominent when mechanical traction is used.
2. After the cable laying is completed, the head of the cable is not produced in time due to the limitation of on-site construction conditions, so that the unsealed cable breakage is exposed to the air for a long time, even immersed in the water, so that the water vapour enters the cable in large quantities.
3. In the normal operation of the cable, if a breakdown occurs for some reason, the water in the cable trench will enter the cable inside the fault point; In civil construction, especially in construction sites where large construction machinery is used, cable breakage or breakdown accidents caused by various human factors are not uncommon. In the event of such an accident, cable insulation is severely damaged and the cable is also flooded.