What should we do if the XLPE cable gets wet?
In urban power grid renovation projects, polyethylene insulated cables have been widely used. However, due to the particularity of the cable, there are special requirements for the installation, operation and maintenance of the cable. Moisture of the cable reduces the insulation resistance of the cable, which will cause an important aspect of the operation of the cable line. So how to deal with the damp XLPE insulated cable? The following is a friend to share how to deal with the moisture of xlpe cable.
The cross-linked polyethylene cable uses chemical or physical methods to transform the cable insulation polyethylene molecule from a linear molecular structure to a main network molecular structure, that is, the thermoplastic polyethylene is transformed into a thermosetting cross-linked polyethylene, thereby greatly improving its performance. Heat resistance and mechanical properties reduce its shrinkage, make it no longer melt after being heated, and maintain excellent electrical properties.
Hazard of damp cables:
Moisture or water entering the cable will cause the moisture on the surface of the plastic insulation layer or the surface of the conductor to cause “water branches” in the direction of the electric field under the action of a strong electric field. The water branches cause the insulation to age, and at the same time, the water branches gradually extend to the inside of the insulation, and This situation can accumulate in the insulation and produce a cumulative effect. When this cumulative effect reaches a certain level, it will develop into an “electric tree”, which will eventually lead to the penetration and breakdown of the insulation. Especially when the surface of the conductor contains water, due to the higher temperature, the development of water branches is triggered faster, which will accelerate the aging of the plastic insulation. After the cross-linked polyethylene cable enters the plastic outer sheath, water will enter the metal sheath, which will cause chemical and electrochemical corrosion to the metal sheath, which will eventually damage the metal sheath and cause the water to impregnate the insulating layer. Cause insulation aging and breakdown.
Reasons for cable damp:
1. The sealing of the cable end cap is not tight or the cable end cap is damaged by external force during the process of cable transportation and laying.
2. The cable sheath is damaged by external force during cable transportation or laying.
3. During the cable test or operation, the cable insulation breaks down and destroys the cable sheath.
4. In the process of making cable heads (including terminal heads and intermediate joints), due to the negligence of the construction personnel, the newly processed cable ends may accidentally fall into the stagnant water on site.
Moisture-proof measures for cables:
1. xlpe cable manufacturers are required to strictly control cable materials and manufacturing processes, and try their best to control the presence of micropores and impurities.
2. In the process of transporting and laying cables, check the cable end caps strictly to prevent loosening and falling off. For high-voltage cables, use metal caps to seal them.
3. Before laying the cable, clean the cable trench and pipeline to remove the accumulated water, and take protective measures when laying, and put a protective mouth at the cable inlet.