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Treatment method of cross-linked polyethylene power cable damp

June 04, 2021

In the urban power grid reconstruction project, cables, especially polyethylene insulated power cables, have been widely used. However, due to the particularity of cables, there are special requirements for the installation, operation and maintenance of cables. The cable insulation resistance decreases due to damp or water inflow, which is an important aspect that causes the operation accident of the cable line.
Causes and hazards of cable moisture and water.

(1) when the whole newly imported cable leaves the factory, both ends are sealed with plastic gland bushing, but after it is used for a period at the construction site according to the actual situation, the rest of the part is simply wrapped with plastic cloth. Because it is usually placed in the open air and the seal is not good, it is inevitable that water vapor will penetrate into the cable after a long time.

(2) when laying cables, it is necessary to cross roads, bridges, culverts and so on frequently. Due to weather or other reasons, a lot of water often accumulates in the cable trench. During the laying process, inevitably, cable head will be immersed in water, which will cause water to enter the cable due to lax binding or damage of plastic cloth; In addition, when pulling and threading pipes, sometimes the outer sheath and even the steel rod are scratched, which is especially prominent when mechanical traction is used.

(3) after the cable laying is completed, the cable head production cannot be carried out in time due to the limitation of on-site construction conditions, so that the cable fracture without sealing treatment is exposed to the air for a long time and even immersed in water, make a large amount of water vapor enter the cable.

(4) during the manufacturing process of cable head (including terminal head and intermediate head), due to the negligence of construction personnel, the newly processed cable end sometimes accidentally falls into the accumulated water on site.

(5) in the normal operation of the cable, if breakdown and other faults occur for some reason, the water in the cable trench will enter the inside of the cable along the fault point; In the civil construction, especially in construction sites that use large construction machinery, cable damage or breakdown accidents caused by various human factors are also common. When such accidents occur, the cable insulation is seriously damaged, which will also cause the cable to enter water.

After the cable enters the water, under the action of electric field, aging will occur, which will eventually lead to cable breakdown.

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