- Classification of wires and cables
There are thousands of types of wire and cable products, which are used in all walks of life. There are two general uses for them, one is to transmit current and the other is to transmit signals. The main technical performance indicators for transmission current cables are conductor resistance and withstand voltage performance; the main technical performance indicators for transmission signal cables are transmission performance-characteristic impedance, attenuation and crosstalk. Of course, the transmission of signals mainly relies on electric current (electromagnetic waves) as the carrier. Now with the development of science and technology, light waves can be used as the carrier for transmission.
Generally speaking, cables can be divided into six categories:
- Cables for electrical equipment
Connecting wires used for electrical equipment, with internal wiring or external wiring.
- Power cable
Also known as power cable, used to transmit electric energy: it is often laid underground (urban electric power transmission).
- Overhead wire (bare wire)
Also known as bare wire, it is used for special input of electric energy; it is often used for overhead laying, which has low cost.
- Communication cable
Used to transmit electrical signals; often laid underground or overhead.
- Enameled wire (winding wire)
Also known as winding wire, it is used in motor windings to convert electrical energy into mechanical energy.
- Optical woven optical cable
It is used to transmit optical signals. Because of its low attenuation performance, it is often used as the backbone of long-distance communication.
Second, the meaning of wire and cable specifications and models
- Model and name
RV－Copper core vinyl chloride insulated connecting cable (wire)
AVR－Tinned copper core polyethylene insulated flat connecting flexible cable (wire)
RVB－Copper core PVC flat connecting wire
RVS-copper core PVC stranded connecting wire
RVV－Copper core PVC insulated PVC sheathed round connecting flexible cable
ARVV－Tinned copper core PVC insulated PVC sheathed flat connecting flexible cable
RVVB－Copper core PVC insulated and sheathed flat connecting flexible cable
RV-105 copper core heat-resistant 105oC PVC insulated PVC insulated flexible connection cable
AF-205AFS-250AFP-250 silver-plated polychloroethylene fluoride plastic insulation, high temperature resistance -60oC~250oC connecting flexible wire
- The meaning of specification notation
The specifications are expressed by the number of cores, nominal cross-section and voltage level
①Single-core branch cable specification representation: the number of cables in the same loop* (1*nominal section), 0.6/1KV, such as: 4*(1*185)+1*95 0.6/1KV
②The specification of multi-core stranded branch cable: the number of cables in the same loop * nominal cross section, 0.6/1KV, such as: 4**185+1*95 0.6/1KV
Wire and cable specification model description
| Model | Name | use |
| BX（BLX）
BXF（BLXF） BXR |
Copper (aluminum) core rubber insulated wire
Copper (aluminum) core neoprene rubber insulated wire Copper core rubber insulated cord |
Suitable for electrical equipment and lighting devices with AC 500V and below or DC 1000V and below |
|
BV（BLV） BVV（BLVV） BVVB（BLVVB） BVR BV-105 |
Copper (aluminum) core PVC insulated wire Copper (aluminum) core PVC insulated PVC sheathed round wire Copper (aluminum) core PVC insulated and sheathed flat wire Copper (aluminum) core PVC insulated cord Copper core heat-resistant 105°C PVC insulated cord |
Suitable for all kinds of AC and DC electrical installations, electrical meters, instruments, telecommunications equipment, power and lighting circuits for fixed laying |
|
RV RVB RVS RV-105 RXS RX |
Copper core PVC insulated cord Copper core PVC insulated parallel cord Copper core PVC insulated stranded flexible wire Copper core heat-resistant 105°C PVC insulated flexible connecting wire Copper core rubber insulated cotton yarn braided twisted flexible wire Copper core rubber insulated cotton yarn braided round flexible wire |
Suitable for the connection of various AC and DC electrical appliances, electrical instruments, household appliances, small electric tools, power and lighting devices |
|
BBX BBLX |
Copper core rubber insulated glass wire braided wire Aluminum core rubber insulated glass wire braided wire |
Applicable voltages are 500V and 250V respectively, which are used for indoor and outdoor fixed installation or pipe laying |
Note: B (B)-the first letter represents wiring, and the second letter represents glass fiber weaving.
V (V)-The first letter represents polyethylene (plastic) insulation, and the second letter represents polyethylene sheath.
L(L)——Aluminum, if there is no L, it means copper
F (F)-compound type
R-flexible cord
S-twisted pair
X-insulating rubber
Third, the basic structure of the cable
Generally, the most basic structure of a cable includes conductor, insulating layer and outer protective layer. Add another structure according to requirements, such as shielding layer, inner protective layer or armor layer, etc., and add some filling materials for the roundness of the cable. A conductor is a carrier for transmitting current or signals, and other structures are used for protection. There are three types of protection performance according to the needs of cable products. One is to protect the various units of the cable itself from mutual or reduce influence, such as withstand voltage, heat resistance, anti-loss caused by electromagnetic fields, and anti-signal interference of communication cables. The other type of protection is to protect the current in the conductor from affecting the outside, such as preventing current leakage and electromagnetic wave leakage, etc.; the last type of protection is to protect the outside from affecting the inside of the cable, such as compression resistance, tensile resistance, heat resistance, weather resistance, Flame-resistant, waterproof, anti-electromagnetic wave interference, etc.The following is a brief introduction to the structural units of the power cable.
1) Conductor (or conductive core): its function is to conduct current. There are solid core and stranded. The materials include copper, aluminum, silver, copper-clad steel, aluminum-clad steel, etc. The main ones are copper and aluminum. The conductivity of copper is much better than that of aluminum. The national standard requirements for the resistivity of copper conductors are not less than 0.017241Ω.mm2/m (at 20°C), and the resistivity of aluminum conductors is not less than 0.028264Ω.mm2/m (at 20°C).
2) Refractory layer:
Only fire-resistant cables have this structure. Its function is that the cable can withstand a certain period of time in a fire, giving people more time to use electricity when they escape. The material currently used is mainly mica tape. In a fire, the cable will burn quickly. Because the mica sheet of the mica tape is resistant to high temperature and has an insulating effect, it can protect the conductor from running for a certain period of time in a fire.
The following is a brief introduction to the structural units of the power cable.
1) Conductor (or conductive core): its function is to conduct current. There are solid core and stranded. The materials include copper, aluminum, silver, copper-clad steel, aluminum-clad steel, etc. The main ones are copper and aluminum. The conductivity of copper is much better than that of aluminum. The national standard requirements for the resistivity of copper conductors are not less than 0.017241Ω.mm2/m (at 20°C), and the resistivity of aluminum conductors is not less than 0.028264Ω.mm2/m (at 20°C).
2) Refractory layer:
Only fire-resistant cables have this structure. Its function is that the cable can withstand a certain period of time in a fire, giving people more time to use electricity when they escape. The material currently used is mainly mica tape. In a fire, the cable will burn quickly. Because the mica sheet of the mica tape is resistant to high temperature and has an insulating effect, it can protect the conductor from running for a certain period of time in a fire.
4) Shielding layer:
Outside the insulating layer and inside the outer protective layer, the role is to limit the electric field and electromagnetic interference. For different types of cables, the shielding materials are different, mainly: copper wire braiding, copper wire winding, aluminum wire (aluminum alloy wire) braiding, copper tape, aluminum foil, aluminum (steel) plastic tape, steel tape, etc. Longitudinal package and so on.
5) Filling layer:
The main function of the filling is to make the cable round and stable. The filling of some cables also plays a role in water blocking and fire resistance. The main materials are polypropylene rope, glass fiber rope, asbestos rope, rubber, etc. There are many types, but one of the main performance requirements is a non-hygroscopic material, which of course cannot conduct electricity.
6) Inner protective layer:
The function of the inner protective layer is to protect the insulated core from being damaged by the armor layer or the shielding layer. The inner protective layer has several forms such as squeezing, wrapping and vertical wrapping. For those with high requirements, the squeezed bag is used, and for those with low requirements, the wrapping or vertical bag is used. Nowadays, there are many kinds of materials used for wrapping. For example, the inner sheath of steel tape armor is wrapped with PVC tape, or polypropylene tape (very thin, made of particles on the surface to make up the thickness). of. Can it be used? The main problem is the market positioning of cable product quality. This is different from whether the silane cross-linked insulated core is distinguished by color or by color band. The properties are somewhat the same, but not all. The use of PVC tape and polypropylene tape for wrapping tape here has an impact on product quality. Whether the silane cross-linked insulated core is distinguished by color or by color band has little effect on product quality, mainly due to the needs of users.
7) Armour layer:
The role of the armor layer is to protect the cable from being damaged by external forces. The most common are steel tape armor and steel wire armor, as well as aluminum tape armor and stainless steel tape armor. The main function of steel tape armor is compression resistance, and the main function of steel wire armor is tension resistance. According to the size of the cable, the thickness of the steel strip used for armoring is different, which is stipulated in various cable standards.
8) Outer sheath:
The component that plays a protective role on the outermost layer of the cable.
There are three main types: plastic, rubber and metal. Among them, the most commonly used plastics are polyvinyl chloride plastics and polyethylene plastics, as well as flame-retardant, low-smoke and low-halogen type, and low-smoke and halogen-free type according to cable characteristics.
The above is the basic structure of general cables. Some types of cables have simpler structures, only conductors and insulation layers, and some cables do not have armor or shielding layers. Therefore, various types of cables are produced according to different structures and materials. There are thousands of types of wire and cable products, which are used in all walks of life. There are two general uses for them, one is to transmit current and the other is to transmit signals. The main technical performance indicators for transmission current cables are conductor resistance and withstand voltage performance; the main technical performance indicators for transmission signal cables are transmission performance-characteristic impedance, attenuation and crosstalk. Of course, the transmission of signals mainly relies on electric current (electromagnetic waves) as the carrier. Now with the development of science and technology, light waves can be used as the carrier for transmission.