cableThe direct cause of the malfunction is insulation degradation and breakdown. There are many factors that can reduce the sensitivity of insulation, and based on practical experience, the following situations can be summarized.

1. External damage. For example, construction of cable laying and installation that is not qualified can easily cause mechanical damage, and in civil construction, underground cables are also prone to cable damage and other operations. Sometimes, if the damage is not severe, it may take several months or even years to cause breakdown faults in the damaged area. Sometimes, serious damage may occur, leading to short circuit faults that directly affect the safety production of electrical units.

2. Insulation is damp. For example, if the cable joints are not made properly and in humid climates, the joints can cause water or water vapor to mix with the ground water tree for a long time under the action of an electric field, resulting in gradual damage to the insulation strength and cable failure.

3. Chemical corrosion. In the area of acid-base interaction, long-term exposure to chemical or electrochemical corrosion caused by armored cables, wires, or corrosion protection layers and outer protective layers often leads to poor insulation of the protective layer and cable failure.

4. Long term overloaded operation. Overload operation, due to the current, the thermal effect of the load current passing through the cable will inevitably cause heating in the conductor. At the same time, skin effect and eddy current loss of charges, as well as dielectric loss of steel armor, can also generate additional heat, thereby increasing the temperature of the cable.

5. Cable joint malfunction. Cable joints are the weak links caused by frequent cable joint failures by cable personnel, resulting in direct negligence. In the manufacturing method of cable joints, if the crimping is not tight and the heating is not sufficient, the insulation of the cable head may decrease, causing accidents.