Electric cable usually consists of several or numerous sets of wires. Specifically, it consists of two different definitions. Frist, it consisted of one or more insulated conductors and an outer insulating protective layer to transfer power or information from one location to another. Another, it is usually cable that is twisted from several or several sets of wires (at least two in each set). Each set of wires is insulated from each other and often twisted around a center. The entire outer bread has a height. Insulated overlay. The cable has the characteristics of internal energization and external insulation.
Electric cable also has diverse types, such as power cable, control cable, compensation cable and so on. They are composed of single or multiple strands of wire and insulation to connect circuits, electrical appliances, etc.
And here is talking about the causes for cable aging, common cable faults and correspondingly countermeasures.
① External force damage.
Judging from the operational analysis in recent years, especially in Shanghai Pudong, where the economy is developing at a high speed, quite a number of cable faults are due to mechanical damage.
② Insulation is damp.
This is equally common and occurs generally at cable joints in direct buried or drained pipes. For example, if the cable joint is unqualified and the joint is made under humid climatic conditions, the joint will be a lot of water or mixed with water vapor. After a long time, the water branch will form under the action of the electric field, which will gradually destroy the insulation strength of the cable and cause malfunction.
③ Chemical corrosion.
The cable is directly buried in an acid-base area, which often causes the cable armor, lead or outer sheath to be corroded. The shielding layer is chemically corroded or electrolytically corroded for a long time, causing the protective layer to fail and the insulation to be lowered. Cable failure. Chemical: The corrosion of the cable in the unit is quite serious.
④ Long-term overload operation.
Overload operation, due to the thermal effect of the current, the load current will inevitably lead to the heating of the conductor when passing through the cable. At the same time, the skin effect of the charge and the eddy current loss of the steel crucible and the loss of the insulating medium will also generate additional heat, thereby increasing the cable temperature.
⑤ The cable connector is faulty.
Cable joints are the weakest link in cable lines, and cable joint failure caused by direct personnel failure (poor construction) often occurs. During the process of making the cable joints, if the joints are not tightly pressed or insufficiently heated, the insulation of the cable head will be reduced, causing an accident.
⑥ Environment and temperature.
The external environment and the heat source where the cable is located can also cause excessive cable temperature, insulation breakdown, and even an explosion.
Common faults in cable lines are automated damage, insulation damage, insulation moisture, insulation aging deterioration, overvoltage, cable overheating faults, etc. And the most direct cause of cable failure is insulation breakdown and breakdown. Specifically:
① Overload operation.
Long-term overload operation will increase the cable temperature, insulation aging, resulting in breakdown of insulation and reduced construction quality.
② Electrical aspects
The cable head construction process can not meet the requirements, the cable head sealing performance is poor, moisture invades the cable inside, the cable insulation performance is degraded; when the cable is laid, no protective measures are taken, the protective layer is damaged, and the insulation is lowered.
③ In terms of civil construction, the drainage of the wells and trenches is not smooth, the cables are soaked by water for a long time, and the insulation strength is damaged; the work well is too small, the bending radius of the cable is not enough, and the external force is damaged by long-term extrusion. Mainly the mechanical construction of the municipal construction, the bruise cut the cable.
This cause the protective layer is subjected to chemical corrosion or cable corrosion for a long time, resulting in failure of the protective layer and lowering of the insulation.
⑤ The cable itself or the cable head accessory is of mediocre quality, the cable head is poorly sealed, the insulating glue is dissolved, and the cracking occurs, resulting in the resonance phenomenon of the station. The line disconnection fault causes the line phase capacitance and the ground capacitance to resonate with the distribution transformer excitation inductance. Loop, thereby exciting ferromagnetic resonance.
We can choose some electric fittings to protect electric cable, such as the cable protection sleeves with good quality. Because good cable protection sleeves have good insulation performance, high chemical stability, no rust, no aging, adaptable to harsh environments. It can protect the electric cable well.
And we also can use the electrical insulator, which is a machine installed between conductors of different potentials or between conductors and ground potential members, capable of withstanding voltage and mechanical stress.
When the above faults occur on the line, the power supply of the faulty cable should be cut off, found the fault points, inspected and analyzed them, and then the repair and carry out them. The cut-out can be resumed after the faults are removed.
I hope this article will be able to notice the danger of the cable, and when we choose the cable we also should buy some cable accessories to protect not only the electric cable but ourselves.