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What are the Pre-Control Measures for Cables?

Feb. 14, 2020

With the increasing number of cable lines and the increase in operating life, cable failures have gradually increased, and the cable body, cable accessories, cable auxiliary equipment and other failures that occur during cable operation have also increased significantly. Due to the excellent performance of the Mineral Insulated Cable, it is suitable for lines with a rated voltage below 1000V. China Mining Cable Manufacturer said that the durability and reliability of mineral cables are more advantageous than traditional cables. And the mineral cable has a large current carrying capacity, water, explosion-proof, corrosion resistance, high operating temperature, corrosion resistance, and overload protection, so its life is longer than traditional cables. The construction of power cables into the ground is the direction of the modern development of the city. The locations of cable failures are mainly concentrated in insulation, accessories and outer sheaths.

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Insulation failure reason analysis

1. Insulation failure

The insulation aging of cables mainly occurs in the late stage of operation, and generally occurs in cable lines that have been in operation for 15 years or more, resulting in a significant increase in cable failure rates. Insulation aging is mainly divided into dendritic aging, electrothermal aging and insulating material aging. The air gap inside the cable insulation medium is released under the action of the electric field to reduce the insulation. When the insulation medium is ionized, ozone, nitrate and other chemicals are generated in the air gap, which corrode the insulation layer. At the same time, the moisture in the insulation decomposes the insulation fibers, causing Insulation strength decreases.

2. Overheating will accelerate insulation deterioration. The electrical dissociation generated by the air gap inside the cable insulation will cause local overheating, carbonize the insulation material, and cause the insulation strength to decrease. Cable overload is an important factor for cable overheating. Cables installed in poorly ventilated areas such as cable dense areas, cable trenches, and cable tunnels, cable paths running parallel to or crossing thermal pipes, and without effective thermal insulation measures will overheat the cables and accelerate insulation damage. Recommended products: high voltage cables

3. For a long time when the cable insulation is operated under the action of electricity and heat, its physical properties will change, which will cause its insulation strength to decrease or its dielectric loss to increase, which will eventually cause the insulation to collapse and fail. The main causes of insulation aging are:

(1) Improper selection of the cable causes the cable to work under overvoltage for a long time;

(2) The cable line is close to the heat source, which makes the cable part or the entire cable line heated for a long time and prematurely ages;

(3) The cable works prematurely in an environment with an adverse chemical reaction with the insulation;

(4) When multiple cables are operated in parallel, one or more of them are not in good contact, causing other cables in parallel to operate in overload.

(5) When the cable accessories are manufactured, the cable connection tube is not crimped firmly, resulting in an increase in contact resistance and overheating.

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Jennifer leo