The we contacted in the cable , both the outer sheath and the inner sheath have a certain insulating effect. So what is the function of the cable insulation layer? The main function of the insulating layer of cable is to insulate the conductors in the cable from the surrounding environment or adjacent conductors. cable cable core is a conductor. In order to prevent the exposed wire from short circuit causing equipment damage, and the damage to wires exceeding the safe voltage to people, the cable must be added with an insulating protective layer (non-conductor). The resistivity of the metal conductor in the
The resistivity of the insulator is very small; the resistivity of the insulator is extremely high. The reason why insulators can be insulated is that the positive and negative charges in the molecules of the insulator are tightly bound, there are very few charged particles that can move freely, and their resistivity is very large. Therefore, in general, the macroscopic current formed by the movement of free charges under the action of an external electric field can be ignored, and it is considered to be non-conductive substances.
For the insulator, there is a breakdown voltage, which can give the electrons enough energy to stimulate it. Once the breakdown voltage is exceeded, this material will no longer be insulated.
In many supplier announcements of State Grid notifications, we can often see the notifications of cable companies: the thickness of the produced power cable insulating layer is unqualified. So what impact does the unqualified insulation layer have on the cable?
1. Shorten the service life of wire and cable products
This issue is easy to understand. After long-term operation, especially in direct burial, immersed in water, open-air or easily corrosive environments, due to long-term corrosion of external media, the insulation level and mechanical level of the sheath will be reduced. Additionally, conventional sheath tests or line grounding failures may cause thin clicks to penetrate. This will lose the protection of the cable sheath. In addition, internal consumption cannot be ignored. Long-term live wires and cables will generate a lot of heat. Here we add a little more common sense that the allowable operating temperature of conductors is 70°C, and the long-term use temperature of PVC should not exceed 65°C. Therefore, wires and cables are actually in a state of "internal and external troubles".
2. Increased difficulty in laying
With the development of global industry, more and more environments require that the outer diameter of high-voltage cable products must be small. During the laying process, there must be gaps to dissipate the heat generated after the wires and cables are energized. Excessive sheath thickness will increase the difficulty of laying, so the thickness of sheath must strictly comply with relevant standards, otherwise it will have no protective effect on wires and cables. You can't just pursue its thickness.
According to the above two analyses, it is not difficult to see that one characteristic of product quality is reflected in the appearance quality of the product. Whether it is power cables or simple wires, the quality of the insulation layer must be paid attention to in production and strictly control and inspect them.
However, this phenomenon occurs again in life: the surface of lighting cables and low-voltage cables are covered with a layer of insulating leather made of plastic or rubber. However, the high-voltage cables in the wild do not cover the insulating skin (the high-voltage line entering the community is equipped with an insulating layer, and the insulating layer is only an auxiliary function. It is not safe, so you must ensure a safe distance) The surface is smooth and shines under the sunlight. Why do hundreds of volt wires have insulating skins, while tens of thousands of volts and hundreds of thousands of volts do not contain insulating skins?
explains with physical knowledge: This is because, at too high voltage, some materials that are originally insulating, such as rubber, plastic, dry wood, etc., will also become conductors and will not play an insulating role. Wraping insulating skin on high-voltage cables is equivalent to wasting money and things in vain. The surface of the high-voltage wire is not covered with insulating skin. If you hang it on a high iron tower, it may leak electricity due to contact with the iron tower. To prevent this phenomenon, high-voltage wires are always hung under a long list of well-insulated porcelain bottles to insulate the high-voltage wires from the tower. In addition, when installing high-voltage cables, you must not drag them on the ground. Otherwise, due to friction between the wire and the ground, the originally bare insulation layer will be damaged and many burrs will appear. These burrs will cause tip discharge , causing leakage.
It can be seen from this that the insulation layer of the cable is set according to the needs of the cable. Moreover, the thickness of the cable sheath is not qualified if it is below the standard requirements, and the thickness exceeding the standard requirements is not qualified if it is not qualified. Therefore, during the production process, we need to carefully operate the equipment and strictly control the insulation thickness according to the standards. This not only saves resources for the enterprise, reduces material consumption, and increases profits, but also ensures the quality of the cable and creates high-quality and low-priced products. Of course, during use, you should also pay attention to whether the insulating layer is damaged. If it is damaged, it will affect the insulation performance and cannot be used normally.
Qingdao Huaqiang Cable is a manufacturer specializing in the production of wires and cables. The company's Huayu brand wires and cables have all the performances of International Electrical Commission and national standards. The leading products include: aluminum alloy cable , cross-linked power cable, polyvinyl chloride insulated power cable, control cable, computer cable, mineral insulated cable, electrical equipment wires and cables and other types of cables. You can also process and customize the required special cable according to user needs.
