Views:215 Author:Site Editor Publish Time: 2020-09-29 Origin:Site
With the development of the industry, the reliance on electric energy is also increasing. In order to guarantee the electricity demand of various industries and regions, the demand for wires laying length has also become huge, and potential safety hazards have gradually attracted people's attention. And nowadays, the damage caused by cable failures is getting bigger and bigger. We often use some fault indicators for fault inspection. Common fault indicators include short circuit fault indicators, ground fault indicators, etc.
According to the location of the cable fault, the general cable faults mainly include the main insulation fault of the cable and the cable outer sheath fault. There are also some common failures such as low resistance ground short circuit fault, low resistance short circuit fault, disconnection fault, high resistance ground fault, high resistance short-circuit fault, flashover faults, leakage faults, intermittent faults, etc.
1) Mechanical Damage
Cable failures caused by mechanical damage account for a large proportion of cable accidents. Some mechanical damages were minor and did not cause failures at the time, but the damaged parts developed into failures months or even years later. The main causes of cable mechanical damage are as follows:
A. Damage during installation: accidentally touch the cable during installation, strain the cable due to excessive mechanical traction, or damage the cable due to excessive bending of the cable.
B. Directly damaged by the external force: the urban construction is carried out on the cable path or near the cable after installation, so that the cable is directly damaged by the external force.
C. The vibration or shock of the driving vehicle will cause the lead (aluminum) package of the underground cable to crack.
D. Damage caused by natural phenomena: such as the expansion of the insulating rubber in the intermediate joint or terminal head and the expansion of the shell or cable sheath. The natural stroke of the cable causes the cable sheath to be installed on the nozzle or bracket to be scratched.
2) The Insulation is Damp.
If the insulation becomes damp, it will cause malfunction. The main causes of damp cables are:
A. Water ingress due to unsealed structure or poor installation of the connector box or terminal box.
B. The cable is poorly manufactured, and the metal sheath has small holes or cracks.
C. The metal sheath is pierced or corroded by foreign objects.
3) Insulation Aging and Deterioration
The internal air gap of the cable insulation medium is released under the action of the electric field, which causes the insulation to drop. When the insulating medium ionizes, chemical products such as ozone and nitric acid are generated in the air gap, which corrode the insulation, the moisture in the insulation causes the insulating fiber to hydrolyze, causing the insulation to drop.
The atmosphere and internal overvoltage will cause cable insulation to break down and form a fault. The breakdown point is generally defective.
5) Poor Design and Production Process
The waterproof and electric field distribution design of the intermediate joint and the terminal head is not thorough, the material selection is improper, the workmanship is not good, and the production is not in accordance with the regulations will cause the cable head to malfunction.
6) Material Defects
Material defects are mainly manifested in three aspects. One is the problem of cable manufacturing, the defects left by the lead (aluminum) sheath. The second is the defect in the manufacturing of cable accessories, for example, cast iron parts have blisters, ceramic parts have insufficient mechanical strength, other parts do not meet specifications or are not sealed during assembly, etc. The third one is poor maintenance and management of insulating materials, resulting in damp, dirty and aging of cable insulation.
One of the biggest consequences of cable failure is fire. According to statistics, 40% of fires are caused by unqualified wire and cable short circuit. Cable leakage caused by power short circuit can also cause electric shocks and endanger lives. And cable faults will also have an impact on the electricity consumption of various industries, and will damage electrical equipment and electronic devices, which will cause irreparable losses to the national economy.
For short circuit and earth faults, we need professional earthing and short circuiting devices for testing. Our company mainly produces cable fault indicators and fault passage indicators to accurately help you detect faults.