NOYAFA Electronic specializing in testing instruments and cable testers for 16 years
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NOYAFA Electronic specializing in testing instruments and cable testers for 16 years
Author: Noyafa–CCTV Monitor Tester
What are the causes of underground power cable faults caused by cable faults? Causes of cable faults Now that electricity has penetrated into people's lives, power cable faults exist at any time; and the factors that cause power cable faults are complex and changeable. Here, after sorting and analysis, the reasons for underground power cable faults can be roughly summarized as follows. Category: First, poor design and production process The waterproof and electric field distribution design of the middle and terminal ends of the cable is not well-designed, improper selection of materials, and failure to manufacture according to regulations will cause cable head failure. The second reason for cable failure is mechanical damage. Usually, some mechanical damages are very minor and did not cause a failure at the time. It will take months or even years for the damage to develop into a failure. The main reasons for the mechanical damage of power cables are: (1) Civil construction is carried out on or near the cable path after installation, so that the cables are directly damaged by external forces.
(2) The vibration or impact load of the driving vehicle will also cause the lead (aluminum) package of the underground cable to crack. (3) The cable is accidentally bumped during installation, the cable is pulled by excessive mechanical traction, and the cable is damaged by excessive bending. (4) Damage caused by natural phenomena.
For example, the inner insulating glue of the intermediate joint or the terminal head expands and bursts the outer casing or cable sheath; or the cable sheath installed on the nozzle or bracket is scratched; or due to excessive tension caused by land settlement, the intermediate joint or conductor is pulled off. The third reason for cable failure is that the overvoltage (lightning strike or operating overvoltage) acts on the atmosphere and the internal overvoltage, causing the cable insulation to be broken down, thereby forming a cable failure. In general, the breakdown point is defective.
Fourth, the insulation is damp. After the insulation is damp, it will cause the cable withstand voltage to drop and cause failure. The main reasons for the cable getting wet are: (1) The metal sheath is perforated or stabbed due to corrosion by foreign objects. (2) Water ingress due to unsealed structure or poor installation of joint box or terminal box.
(3) The cable is poorly manufactured, and the metal sheath has small holes or cracks. Reasons for cable failure Fifth, insulation aging and deterioration Insulation aging will cause the cable withstand voltage to drop and cause failure. The main reasons for cable aging are: (1) Power cables are used over time.
(2) The cable is overloaded or the cable is poorly ventilated, causing local overheating and carbonization of the insulation. Among them, cable overload is an important factor for cable overheating. (3) When the oil-impregnated paper insulated cable is laid, the ground is uneven. Due to the existence of the height difference, the insulating oil that is higher will flow to the lower place, which will reduce the insulation performance of the cable at the higher place, resulting in failure.
(4) There is slag or air gap inside the cable insulation medium, and the insulation is lowered due to dissociation and hydrolysis under the action of the electric field. What are the reasons for the failure of underground power cables? Causes of cable failure Shenzhen Noyafa Electronic Technology Co., Ltd.
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