Treatment of XLPE power cable damp

Cables, especially XLPE insulated power cables, have been widely used in urban power grid reconstruction projects. However, due to the particularity of the power cable, there are special requirements for the installation, operation and maintenance of the cable. The cable insulation resistance is reduced due to moisture or water ingress, which is one of the important aspects of cable line operation accidents.

Cause and harm of cable moisture and water ingress

(1) When the new whole reel of cable leaves the factory, its two ends are sealed with plastic sealing sleeves. However, after a section is used at the construction site according to the actual situation, the rest is simply wrapped with plastic cloth. As 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) During xlpe cable laying, it is necessary to often 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 the water, and the water will enter the cable because the plastic cloth is not wrapped tightly or damaged; In addition, the outer sheath or even the steel armor may be scratched during traction and pipe threading, especially when mechanical traction is used.

(3) After the completion of cable laying, due to the limitation of on-site construction conditions, the cable head was not made in time, so that the cable fracture without sealing treatment was exposed to the air for a long time, or even immersed in water, so that a large amount of water vapor entered the cable.

(4) During the manufacturing process of cable head (including terminal head and intermediate joint), due to the negligence of construction personnel, the newly treated cable head sometimes accidentally falls into the ponding on the site.

(5) During the normal operation of the cable, if breakdown and other faults occur for some reason, the accumulated water in the cable trench will enter the cable along the fault point; In civil construction, especially in the construction site where large construction machinery is used, cable damage or breakdown accidents caused by various human factors are also common. In case of such an accident, the cable insulation will be seriously damaged and water will enter the cable.

After water enters the insulated cable, aging will occur under the action of electric field, and finally lead to cable breakdown.