Author: Noyafa–Cable Tester Manufacturer
5 main reasons for underground power cable faults 1. Mechanical damage Cable faults caused by mechanical damage account for a large proportion of cable accidents. Some mechanical damages are very minor and did not cause failures at the time. It takes months or even years for the damage to develop into the five main reasons for underground power cable faults. 1. Mechanical damage Cable faults caused by mechanical damage account for a large proportion of cable accidents. large proportions. Some mechanical damage is so minor that it does not cause a failure at the time, and it takes months or even years for the damage to develop into a failure.
The main reasons for the mechanical damage of the cable are: (1) Damage during installation. The cable is accidentally bumped during installation; the cable is pulled by excessive mechanical traction; the cable is damaged by excessive bending. (2) Directly damaged by external force.
Carry out civil construction on or near the installed cable path, so that the cable is directly damaged by external force. (3) The vibration or impact load of the driving vehicle will also cause the lead (aluminum) package of the underground cable to crack. (4) Damage caused by natural phenomena.
For example, the inner insulating rubber of the intermediate joint or terminal head expands and bursts the outer casing or cable sheath; the cable sheath installed on the nozzle or bracket is scratched; due to excessive tension caused by land settlement, the intermediate joint or conductor is pulled off. 2. Insulation damp When 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) Water ingress due to unsealed structure or poor installation of the joint box or terminal box.
(2) The cable is poorly manufactured, and the metal sheath has small holes or cracks. (3) The metal sheath is punctured or corroded by foreign objects. 3. 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) The slag or air gap inside the cable medium is freed and hydrolyzed under the action of the electric field. (2) The cable is overloaded or the cable communication is poor, causing local overheating. (3) The insulation of the oil-impregnated paper insulated cable is lost.
(4) The power cable is used over time. 4. Overvoltage Overvoltage can cause electrical breakdown of defective cable insulation and cause cable failure. The main reasons are: atmospheric overvoltage (such as lightning strike); internal overvoltage (such as operating overvoltage).
5. Poor design and production process The poor design and production process of the cable head and the middle will also cause cable failure. The main reasons are: the design of electric field distribution is not thorough; improper selection of materials; poor technology, not according to regulations.
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