By hmimcu 
Cable structure composition
Wire and cable product structure components, on the whole, can be divided into wire, insulation, shielding and sheathing of the four main structural components as well as filler components and pulling elements. According to the use of the product requirements and applications, some products are extremely simple structure, only a structural component of the wire, such as overhead bare wire, contact network wire, copper and aluminum busbar (bus), etc.; these products are relying on the installation of the external electrical insulation is laid with insulators and the space distance (i.e., the use of air insulation) to ensure that.
The vast majority of wire and cable products are identical in cross-section (cross-section) shape (ignoring manufacturing errors), long products, which is due to the characteristics of the system or equipment is used as a composition line or coil and decided. Therefore, to study and analyze the structural composition of cable products, it is only necessary to observe and analyze them from their cross-sections. Here to analyze the cable structure composition and cable materials in detail:
1, cable structure composition: wire
Conductor is the product for current or electromagnetic wave information transmission function of the most basic essential main components. Conductor is the conductive core of the abbreviation.
Cable conductor materials include what: the material of the conductor is generally made of copper, aluminum and other non-ferrous metals with excellent conductivity. In the past thirty years the rapid development of optical communication networks with optical fiber cable, optical fiber as a conductor.
2, cable structure: insulation
Insulation is wrapped around the periphery of the wire to play the role of electrical insulation components. That is, to ensure that the transmission of current or electromagnetic waves, light waves only along the conductor line and does not flow to the outside, the conductor has a potential (that is, on the formation of the potential difference between the surrounding objects, i.e., voltage) can be isolated, that is, not only to ensure that the normal transmission of the wire, but also to ensure that the outside world objects and the safety of the person. Conductor and insulation is composed of cable products (except bare wire class) must have two basic components.
Cable insulation material is what: today’s wire and cable, cable insulation material classification is mainly plastic and rubber two categories of surface polymer materials dominant material, derived from a wide range of types of wire and cable products for different uses and environmental requirements. Common wire and cable insulation materials are polyvinyl chloride (PVC) material, cross-linked polyethylene (XLPE), fluorine plastic, rubber material, ethylene propylene rubber material, silicone rubber insulation material.
3, cable structure: sheath
When the wire and cable products installed and operated in a variety of different environments, must have the product as a whole, especially for the insulation layer to play a protective role in the components, which is the protective layer. Because the insulating material is required to have a variety of excellent electrical insulation properties, the material must be required to be extremely high purity, impurity content is very small; often can not take into account its ability to protect the outside world, so for the outside world (i.e., installation, use of occasions and the use of) a variety of mechanical force to withstand or resistance, resistance to atmospheric conditions, resistance to chemicals or oils, the prevention of biological aggression, as well as to reduce the hazards of the fire and so on must be by the Various sheathing structure to undertake. The main functions of cable sheathing are waterproofing, flame and fire resistance, and corrosion protection. Many dedicated to a good external environment (such as clean, dry, no mechanical external force indoor) in the cable products, or insulation materials itself has a certain degree of mechanical strength, weather-resistant products, can be no sheath this component.
Cable sheathing materials which are: cable sheathing materials are mainly rubber, plastic, paint, silicone and a variety of fiber products. Rubber-plastic protective layer is characterized by soft, lightweight, in the mobile cable is extremely widely used. However, since rubber-plastic materials have a certain degree of water permeability, they can only be applied when using polymer materials with high moisture resistance as cable insulation. Then there are some users will ask why in the market to see are plastic as a protective layer? Rubber sheath and plastic sheath characteristics compared: rubber sheath elasticity and flexibility will be higher, aging resistance, but the process is relatively complex. The mechanical properties of plastic sheath, waterproof performance is better, and abundant resources, cheap, easy to process, so the market is more widely used. Industry colleagues need to pay attention to is that there is a class of metal sheath, metal sheath both mechanical protection role and the following to say the role of shielding, but also has corrosion resistance, compressive and tensile properties and water resistance, etc., can prevent moisture and other harmful substances into the cable insulation inside, and therefore is widely used as a poor resistance to humidity of oil-impregnated paper-insulated power cables in the sheath.
4, cable structure: shielding layer
Is a cable product in the electromagnetic field and the external electromagnetic field to isolate the components; some cable products in its internal different pairs (or groups) also need to isolate each other. It can be said that the shielding layer is a kind of “electromagnetic isolation screen”. Over the years, the industry is accustomed to the shielding layer as part of the structure of the shielding layer, cable treasure editorial think should be treated as a separate component. The reason is that in addition to the function of the shield is electromagnetic isolation – that is, cable products in the transmission of information does not diarrhea, not to the outside world instrumentation or other lines of interference; outside the various electromagnetic waves will not enter the cable products through electromagnetic coupling, these functional requirements and the traditional function of the protective layer is different. Also because the shielding layer is not only set up on the outside of the product, but also placed between each pair or multi-pair cable grouping. In recent years, with the rapid development of information transfer systems with wire and cable, as well as the existence of more and more sources of electromagnetic interference in the atmosphere, prompted by the shielded structure of the varieties of exponential growth, we have the shield as a basic component of the cable products in the understanding, has tended to agree.
Cable shielding layer materials: cable shielding layer using metallized paper or semiconductor paper tape as the inner shielding layer, the outer screen layer is sometimes also outside the tie copper tape or braided copper wire tape, braided layer material is generally red copper or tinned copper.
5, cable structure composition: filling structure
Many wire and cable products are multi-core, such as low-voltage power cables most of the four-core, five-core cable (for three-phase system), the city telephone cable is 800 pairs, 1,200 pairs, 2,400 pairs to 3,600 pairs. These insulated wire cores or pairs of cable (or grouped into a cable many times), a shape is not rounded, the second is the insulated wire cores leave a large gap, so it is necessary to join the filler structure in the cable, the filler structure is designed to make the outer diameter of the cable is relatively rounded in order to facilitate the package with the tape, extrusion of the sheath, and also in order to make the cable structure is stable, the internal stone in the use of the cable (manufacturing and laying of tensile, compression and bending) the force uniformity and does not Damage to the internal structure of the cable. Therefore, the filling structure is an auxiliary structure, but it is also necessary, and its material selection and shape design also has detailed provisions.
Cable filling materials: general cable filler including polypropylene tape, non-woven PP rope, hemp rope, or recycled rubber processed from the generally cheaper materials. Can be used as cable filling materials, must have no adverse effect on the insulation core, the material itself does not have hygroscopicity, not easy to shrink, non-corrosive and other characteristics.
6, cable structure: tensile components
Traditional wire and cable products are the use of armor layer of the sheath to withstand external tension or self-weight-induced tension. Typical structure is steel tape armor and steel wire armor (such as submarine cables to be ф8mm thick steel wire, stranded into the armor layer). But fiber optic cable in order to protect the optical fiber from small tensile forces, so as not to have a slight deformation of the fiber and affect the transmission performance, it is set in the optical cable structure of the primary and secondary cladding and special tensile force components. In addition, such as cell phone headset line using fine copper wire or thin copper tape around a synthetic fiber wire extruded outside the insulating layer of the structure, which is the synthetic fiber wire tensile components. In short, in recent years, the development of special small, soft type, while requiring multiple bending, twisting the use of products, tensile components play a major role.