Classification of electric wires and cables
According to the use of three categories:
(1) Electric wires and cables -- The electric wires and cables used in the power system mainly include bare overhead wires, power cables, electric wires and cables used in power equipment, etc.
(2) Communication wires and cables -- The wires and cables used for the information transmission system mainly include local telephone cables, TELEVISION cables, electronic cables, radio frequency cables, optical fiber cables, data cables, or other composite cables.
(3) Electromagnetic wire -- cable, enameled wire, silk covered wire, used for electromagnetic energy conversion.
There are five categories by category:
(1) Bare wire -- pure conductor metal, without insulation and sheath layer, such as steel core aluminum stranded wire, electric locomotive wire, etc., and ground flexible wire.
(2) Power cables -- insulated, armored and sheathed (less than five cores, complex structure). The products are mainly used for the transmission of strong electric energy in the power lines of generation, distribution, transmission, transformation and power supply, with large current (tens to thousands of amps) and high voltage (220V to 500kV and above).
(3) Electrical equipment cables -- a wide variety of specifications, wide application range, use voltage at 1kV and below more, oil/cold/temperature/wear resistance cable, medical/agricultural/mining cable, thin wall wire, etc.
-- Our development direction
(4) Communication cables -- from two-core telephone lines to thousands of pairs of voice, coaxial, optical, data, and even combined communication cables.
The structure size of this kind of product is usually small and uniform, and the manufacturing precision is high.
(5) Electromagnetic wire -- mainly used for various motors, instruments and meters, etc.
Standard code for commonly used wires and cables
GB -- National standard;
JB - Standards for Machinery;
SJ - Electronic nonstandard;
YD -- Standard of Post and Telecommunications Department;
GY -- Radio and Television Department;
MT - Coal Ministry standard;
/T- is recommended
1.PVC plastic wire GB 5023-1997 JB8734-1998 P)
2. Flame retardant wire and cable GB/T19666-2005
3. Halogen free and low smoke wire JB/T10941-2004
4. Electric wires for road vehicles JB/T 8139-1999
5. Indoor telephone lines YD/T840-1996
6. General purpose radio frequency coaxial cables GB/T14864-1993, JB/T10941-2004
7. Network YD/T1019-1999
8. Conductor of cable GB 3956-1997
Structure of wires and cables
1. Cable structure
The vast majority of wire and cable products are cross-sectional (cross-sectional) products with exactly the same shape (ignoring errors due to manufacturing) and in long strips, which are determined by the characteristics used in systems or equipment as forming lines or coils.
Therefore, to study and analyze the structure and composition of cable products, we only need to observe and analyze from its section.
Generally speaking, the structural components of wire and cable products can be divided into four main structural components, namely, conductor, insulating layer, shield and sheath, as well as filling elements and pull-on elements.
According to the use of the product requirements and applications, some product structure is very simple.
(1) Conducting Wire Conducting wire is the most basic and essential main component for the product to carry out current or electromagnetic wave information transmission function.
Conductor is the abbreviation of conducting wire core, made of copper, aluminum, copper clad steel, copper clad aluminum and other non-ferrous metals with excellent conductive performance, with optical fiber as the conductor.
(2) The insulation layer is a member that is coated around the periphery of a conductor and ACTS as an electrical insulation.
That is to ensure that the transmission of current or electromagnetic wave, light wave only along the wire and not flow outside, the conductor on the potential (that is, the potential difference formed on the surrounding objects, that is, the voltage) can be isolated, that is, to ensure the normal transmission function of the wire, but also to ensure the safety of external objects and people.
Conductor and insulation layer are the two basic components that must be used to form a cable product (except bare wire).
(3) Shielding is a component that isolates electromagnetic fields in cable products from external electromagnetic fields;
The cable product of the cable also needs to be isolated from each other within its different wire pairs (or groups).
It can be said that the shielding layer is a kind of "electromagnetic isolation screen".
The conductor shielding and insulation shielding of high voltage cable are to homogenize the distribution of electric field.
(4) Sheath. When wire and cable products are installed and run in various environments, they must have components that protect the product as a whole, especially the insulating layer. This is sheath.
Because the insulation material is required to have a variety of excellent electrical insulation performance, the material must be very high purity, impurity content is very small;
It is often impossible to take into account its ability to protect the outside world, so for the outside (that is, installation, use occasions and in use) all kinds of mechanical force to bear or resistance, atmospheric environment, chemical or oil resistance, the prevention of biological damage, and reduce the damage of fire must be borne by a variety of protective layer structure.
Filling structure (5) a lot of wire and cable products are multicore, these or insulated wire core line to cabling (or grouping many cabling), one is the shape is not round, the second is a large gap between insulation wire core, so must add filling structure when cabling, filling structure is relatively rounded in order to make the cable diameter for package, sheath.
6) Tensile component.
The typical structure is steel - core aluminum strand cable, optical fiber cable and so on.
In short, in recent years, in the development of special small, soft, at the same time require many bending, twisting use of products, tensile components play a major role.