Ⅰ. What is a cable?
Ⅱ. The basic structure of the cable
Ⅲ. The main characteristics of wire and cable
Ⅳ. Common cable types
Ⅴ. What are the categories of wire and cable products?
Ⅵ. The application of the cable
Ⅶ. Advantages and disadvantages of power cables and overhead cables
Ⅷ. Why use power cables?
Ⅸ. How many types of cable wires are there?
Ⅹ. What is the difference between cables and wires?
Ⅰ. What is a cable?
A cable is a component that connects two devices to transmit electrical signals and consists of two or more wires bonded, twisted or braided together. Cables have a wide range of uses, and their functions range from the transmission of electrical energy, electrical signals, and wire products for the conversion of electromagnetic energy.
Power cables usually consist of a core for transmitting power or electrical signals and a sheath for protection and insulation. A cable with a single core and a small diameter is usually called a wire, while a wire without an insulating sheath is called a bare wire. The core in the cable is made of metal that conducts electricity well, usually copper, which is a good conductor, or aluminum, which is less expensive.
Ⅱ. The basic structure of the cable
The basic structure of a power cable consists of four parts: a core (conductor), a protective layer, a shielding layer and an insulating layer.
1. Core
The core is the conductive part of the power cable and is used to transmit electrical energy. It is the main part of the power cable.
2. Protective layer
The function of the protective layer is to protect the power cable from the intrusion of external impurities and moisture, and to prevent the power cable from being directly damaged by external force.
3. Shielding layer
15KV and above power cables generally have a conductor shielding layer and an insulating shielding layer.
4. Insulation layer
The insulation layer is to electrically isolate the wire core from the ground and the wire cores of different phases to ensure power transmission. It is an indispensable part of the power cable structure.
Ⅲ. The main characteristics of wire and cable
1. Mechanical properties
It refers to tensile strength, elongation, flexibility, elasticity, softness, vibration resistance, abrasion resistance and impact resistance. For example: mobile rubber-sheathed soft cables for open-pit mining equipment have excellent tensile strength, elongation, tear strength and wear resistance.
2. Flame retardant performance
It refers to the characteristic that the sample is burned under the specified experimental conditions, and after the fire source is removed, the spread of the flame on the sample is only within a limited range and the characteristic is self-extinguishing. It can achieve flame retardant properties through flame retardant cable materials, flame retardant glass fiber ropes and other materials.
3. Electrical properties
(1) Insulation properties: insulation resistance, dielectric constant, dielectric loss, and withstand voltage characteristics.
(2) Electrical conductivity: Most products require good electrical conductivity, and individual products require a certain range of resistance.
(3) Transmission performance: refers to high-frequency transmission characteristics, anti-interference, etc. For example: frequency conversion cables have good shielding performance.
4. Fire resistance
It means that under the experimental conditions specified in the national standard GB/T19666, the sample is burned in the flame, the flame temperature is 750-800 degrees Celsius, the continuous fire supply time is 90 minutes, and the cooling time is 15 minutes. During this time, the cable will still maintain normal operating performance.
5. Corrosion resistance and weather resistance
It refers to galvanic corrosion resistance, biological and bacterial corrosion resistance, chemical corrosion resistance, sunlight resistance, cold resistance, mildew resistance and moisture resistance. For example, anti-corrosion steel-cored aluminum stranded wire, submersible pump cable, etc. have good corrosion resistance.
6. Thermal performance
It refers to product heat resistance grade, working temperature, heat generation and heat dissipation characteristics of power cables, current carrying capacity, short circuit and overload capacity, thermal deformation and thermal shock resistance of synthetic materials, thermal expansion of materials and dripping performance of coating materials. For example, load-bearing detection cables, silicone rubber insulated high-temperature resistant cables, etc. all have high temperature resistance.
Ⅳ. Common cable types
1. BVR
It means polyvinyl chloride insulated, copper core (soft) cloth wire, often referred to as soft wire. Because the wire is relatively soft, it is often used to connect with the motor in electric dragging and where the wire often moves slightly.
2. BVVB
It means copper core PVC insulated PVC flat sheathed cable. It is suitable for places requiring high mechanical protection and humidity, and can be applied openly or secretly.
3. BVV
It indicates copper core PVC insulated PVC round sheathed cable, copper core (hard) cloth wire. It is often referred to simply as jacketed wire. The single-core is round, and the double-core is flat, which is often used for surface-mounted wires.
4. BV
It means single copper core PVC ordinary insulated wire without sheath. It is suitable for wires and cables used in AC voltage 450/750V and below power devices, household electrical appliances, instruments and telecommunication equipment.
5. RVS
It means copper core PVC stranded connection wire. It is often used in household appliances, small electric tools, instruments, control systems, broadcasting audio, fire protection, lighting and control wires.
6. SYWV
Physically foamed polyethylene insulated cable TV system cables, video (radio frequency) coaxial cables (SYV, SYWV, SYFV) are suitable for closed-circuit monitoring and cable TV projects.
7. RG
It stands for Physically Foamed Polyethylene Insulated Cable. It is often used in coaxial fiber hybrid network (HFC) to transmit data analog signals, as well as video transmission, communication systems and signal control systems.
8. SYV
Solid polyethylene insulated RF coaxial cable. It is suitable for closed-circuit monitoring and cable TV projects.
9. BVVP
It means hard copper core flat type PVC insulated PVC sheath, copper mesh shielded wire.
10. VV (VLV)
It means a copper (aluminum) core PVC insulated PVC sheathed power cable, suitable for laying indoors, tunnels, and trenches. It cannot bear the action of external mechanical force and can be laid directly in the ground.
11. RVVP
It means soft copper core stranded round PVC insulated PVC sheathed soft wire. It is suitable for building intercom, anti-theft alarm, fire protection, automatic meter reading and other projects.
Ⅴ. What are the categories of wire and cable products?
Wire and cable products are mainly divided into the following five categories.
1. Bare wires and bare conductor products
It refers to products with only conductors and no insulation layer, including various metals such as copper and aluminum and composite metal round single wires, stranded wires for overhead transmission lines of various structures, flexible wiring, shaped wires, and profiles.
The main features of this type of product: it is a pure conductor metal, without insulation and sheath layer, such as steel cored aluminum stranded wire, copper-aluminum busbar, electric locomotive wire, etc. Its processing technology is mainly pressure processing, such as smelting, calendering, drawing, stranding/compression stranding, etc. The products are mainly used in the suburbs, rural areas, user main lines, switch cabinets, etc.
2. Power cable
It is used in the main line of the power system to transmit and distribute high-power cable products, including 1~330kV and above various voltage levels and various insulated power cables.
The main features of this type of product: extruding (winding) the insulation layer outside the conductor, such as overhead insulated cables, or twisting several cores (corresponding to the phase wire, neutral wire and ground wire of the power system), such as overhead insulated cables with more than two cores , or add a sheath layer, such as plastic/rubber sheathed wires and cables. Its main process technologies are drawing, stranding, insulation extrusion (wrapping), cabling, armouring, sheath extrusion and so on. There are certain differences in the combination of different processes for various products.
The products are mainly used for the transmission of strong electric energy in the transmission, distribution, transmission, transformation, and power supply lines. The passing current is large (tens of amps to thousands of amps), and the voltage is high (220V to 500kV and above).
3. Communication cables and communication optical cables
Communication cables are cables that transmit telephone, telegraph, television, radio, data and other electrical information. Communication optical cable uses optical fiber (optical fiber) as the light wave transmission medium for information transmission. Radio frequency cables are cables suitable for transmitting radio frequency signals in radio communications, broadcasting and related electronic equipment.
With the rapid development of the communication industry in the past two decades, the products have also developed at an astonishing speed. From the simple telephone and telegraph cables in the past to thousands of pairs of telephone cables, coaxial cables, optical cables, data cables, and even combined communication cables. The structural size of this type of product is usually small and uniform, and requires high manufacturing precision.
4. Magnet wire (winding wire)
It cuts the magnetic line of force in the magnetic field in the form of a winding to induce a current, or passes through the wire used to generate a magnetic field, so it is also called an electromagnetic wire. It includes enameled wire, wrapped wire, inorganic insulated wire, etc. with various characteristics.
It is mainly used in various motors, instruments and meters, etc.
5. Wire and cable for electrical equipment
Wires and cables are used to directly transmit electric energy from the power distribution point of the power system to the power connection lines of various electrical equipment and appliances.
The main characteristics of this type of product are: the widest range of use and the most varieties, and most of them must be combined with the characteristics of the equipment used and the environmental conditions of use to determine the structure and performance of the product. It continues to derive new products for special occasions, such as fire-resistant cables, flame-retardant cables, low-smoke zero-halogen/low-smoke low-halogen cables, termite-proof, mouse-proof cables, oil-resistant/cold-resistant/temperature-resistant/wear-resistant Cables, medical/agricultural/mining cables, thin-walled wires, etc.
Ⅵ. The application of the cable
1. Information transmission system
The wires and cables used in the information transmission system mainly include local telephone cables, TV cables, electronic cables, radio frequency cables, optical fiber cables, data cables, electromagnetic wires, power communication or other composite cables, etc.
2. Mechanical equipment, instrumentation system
Except for overhead bare wires, almost all other products in this part are used, but mainly power cables, magnet wires, data cables, instrumentation cables, etc.
3. Power system
The wire and cable products used in the power system mainly include overhead bare wires, busbars (busbars), power cables (plastic cables, oil-paper cables (basically replaced by plastic power cables), rubber-sheathed cables, overhead insulated cables), branch cables (replacing some busbars), electromagnetic wires, and electrical equipment wires and cables for power equipment, etc.
Ⅶ. Advantages and disadvantages of power cables and overhead cables
1. Advantages
(1) No need to erect towers;
(2) It helps to improve the power factor;
(3) The maintenance workload is small, and frequent inspections are not required;
(4) The power cable runs reliably. Because it is installed in a hidden place such as the ground, it is less damaged by external force, has fewer chances of failure, and the power supply is safe, so it will not cause harm to people.
2. Disadvantages:
(1) The cable is not easy to branch;
(2) Cable faults are concealed and difficult to test;
(3) The repair time is longer after the cable is damaged;
The investment cost of cable line construction is relatively high, which is several times that of overhead cables.
Ⅷ . Why use power cables?
1. To transmit the electric energy from the power plant to the substation, power distribution station and users needs to use overhead lines or cables.
2. In the case of limited space, we should use cables. In order to avoid interference with communication, we should also use cables. In densely populated areas and rivers and other places, we also need to use cables to transmit electric energy in order to facilitate and reduce the difficulty of overhead lines.
Ⅸ. How many types of cable wires are there?
There are more than 20 different types of cables available today, designed for applications ranging from transmission to heavy industrial use. Some of the most commonly-used ones include: Non-Metallic Sheathed Cable. These cables are also known as non-metallic building wire or NM cables.
Ⅹ. What is the difference between cables and wires?
Although the terms wire and cable are often used interchangeably. But technically, a wire is one electrical conductor, while a cable is multiple conductors, or a set of wires wrapped in a sheath. Wires are usually made of aluminum or copper.
