Views:225 Author:Site Editor Publish Time: 2020-10-01 Origin:Site
Cable faults are frequently encountered problems now. Generally, we will install an automated electric wire fault indicator monitoring system for monitoring, and also use some tools to troubleshoot fault points, such as earth fault indicators, fault passage indicators, arc fault indicators, etc. Today we mainly introduce the common causes of mobile cable failures.
The direct cause of common mobile cable failure is the failure caused by the reduction of the insulation. The main factors affecting the degradation of insulation performance are external force damage, insulation humidity, chemical corrosion, long-term overload operation, cable joint failure, temperature and environment, and the natural aging of the cable itself.
Cable failures caused by mechanical damages account for a large proportion of cable accidents. Some mechanical damages are small and do not cause any malfunction at the time. It takes months or even years for the damage to develop into a failure.
The main reasons for cable mechanical damages are:
1) Damaged during installation.
A. The cable is accidentally scratched during installation.
B. Pull the cable with too much mechanical traction.
C. Excessive bending of the broken cable.
2) Direct damage from the external force.
After installation, the civil construction on or near the cable channel is carried out, so that the cable is directly damaged by the external force.
3) The vibration or shock of moving vehicles can also cause cracks in the lead (aluminum) package of underground cables.
4) Damage caused by natural phenomena.
A. For example, the inner insulating rubber of the intermediate joint or the terminal head bursts the casing or the cable sheath.
B. The cable sheath installed on the nozzle or bracket is scratched.
C. The tension caused by the ground subsidence is too large, and the intermediate joint or wire is broken.
When the insulation is wet, it will cause the cable withstanding voltage drop and cause malfunction. The main causes of the cable damp are:
1) The water ingress is caused by an unsealed structure or poor installation of the junction box.
2) The cable is not well done, and there are small holes or cracks in the metal sheath.
3) The metal sheath is pierced or corroded by external objects.
The aging of the insulation will cause the cable voltage to drop and fail. The main causes of cable aging are:
1) The slag or air gap in the cable medium is dissociated and hydrolyzed under the action of an electric field.
2) Overload of offshore cables or poor wind communication causes local overheating.
3) Insulation loss of oil-impregnated paper insulated cables.
4) Excessive use of marine power cables.
The over-voltage will damage the cable insulation and cause cable short circuit. The main reasons are atmospheric over-voltage (such as a lightning strike), internal over-voltage (such as operating over-voltage).
Improper design and manufacture of cable heads and intermediate layers can also lead to cable failure. The main reasons are: the design of the electric field distribution is not careful, the selection of materials is inappropriate, the workmanship is not good and does not meet the specified requirements.
When there are chemical substances or underground sewage in the surrounding environment where the cable is buried, these sewage and chemical substances will corrode the cable, causing the cable sheath and armor to corrode, and ultimately leading to a power short circuit.
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