1, cable structure Generally speaking, the cable consists of the following parts: wires used for current or electromagnetic wave information transmission; Insulating layer, a member covering the electric wire and playing an electric insulation role; A protective layer for protecting the components of the insulating layer; Shielding, a component that isolates the electromagnetic field of the cable from the outside world; Filled structure, component 2 with gap filled between cores, cables are classified according to conductor materials: copper-core cables and aluminum-core cables, and optical fibers are classified according to insulation materials: cable insulation materials are divided into two layers: conductor insulation materials and sheath insulation materials, including fillers between single-core cables. The insulation materials of conductor and sheath of cable can be the same or different. See the following table for specific classification: classification by voltage level: the voltage level of cables is expressed as U0/U(Um), U0 is the conductor-to-ground voltage, U is the conductor-to-conductor voltage, and Um is the maximum value of the highest voltage of the system using the equipment.
Among them, U0 can be divided into two categories according to the duration of system grounding fault. The first type of cables are used in systems where the duration of each single-phase grounding fault does not exceed 65,438+0 minutes, such as small resistance grounding systems and direct grounding systems. The second type of cable is used in systems with long duration of single-phase grounding fault, and it is integrated into neutral grounding through arc suppression coil or high resistance grounding system and ungrounded system. .
2. Knowledge about power cables
Hello: Power cables are used to transmit and distribute electric energy.
It is often used in urban underground power grid, power station outgoing lines, internal power supply in industrial and mining enterprises and underwater transmission lines across rivers and seas. In power lines, the proportion of cables is gradually increasing.
Power cable is a cable product used to transmit and distribute high-power electric energy in the trunk line of power system, including various voltage levels and insulation of 1-500KV. Basic structure The basic structure of power cable consists of four parts: core (conductor), insulating layer, shielding layer and protective layer.
(1) The wire core is the conductive part of the power cable, which is used to transmit electric energy and is the main part of the power cable. (2) Insulation layer The insulation layer is an indispensable part of the power cable structure, which electrically isolates the core from the earth and the cores in different phases to ensure the transmission of electric energy.
(3) Shielding layer 15KV and above power cables generally have conductor shielding layer and insulation shielding layer. (4) Protective layer The protective layer is used to protect the power cable from foreign impurities and moisture and prevent external forces from directly damaging the power cable.
According to the voltage level, it can be divided into medium and low voltage power cables (35kV and below), high voltage cables (1kloc-0/0kV and above), extra-high voltage cables (275-800kV) and extra-high voltage cables (1000kV and above). In addition, according to the current system can be divided into AC cable and DC cable.
According to insulation materials, it is divided into 1, oil-impregnated paper insulated power cable and oil-impregnated paper insulated power cable. Its application history is the longest.
Safe and reliable, long service life and low price. The main disadvantage is that the laying is limited by the drop.
With the development of drip-free impregnated paper insulation, the problem of drip limit has been solved, and the oil-impregnated paper insulated cable can continue to be widely used. 2. The insulation layer of plastic insulated power cable is extruded plastic power cable.
Commonly used plastics are polyvinyl chloride, polyethylene and crosslinked polyethylene. The plastic cable has the advantages of simple structure, convenient manufacturing and processing, light weight, convenient laying and installation, and is not limited by laying drop.
Therefore, it is widely used as medium and low voltage cables, and has a tendency to replace viscous impregnated oil-paper cables. Its biggest disadvantage is dendrite breakdown, which limits its application at higher voltage.
3. The insulation layer of rubber-insulated power cable is made of rubber and various additives, which are fully mixed and wrapped on the conductive wire core, and then vulcanized by heating. Soft and elastic, suitable for frequent movement and small laying bending radius.
Commonly used rubber compounds for insulation include natural rubber-styrene-butadiene rubber compound, ethylene-propylene rubber, butyl rubber and so on. Model description (1) Category: H- local communication cable HP-distribution cable HJ-local cable (2) insulation: Y- solid polyolefin insulation YF-foam polyolefin insulation YP-foam/solid skin polyolefin insulation (3) inner sheath: A- plastic-coated aluminum tape bonded shielded polyethylene sheath S- steel double-layer metal shielded polyethylene sheath V-PVC sheath (3) BVV copper core PVC insulated PVC sheathed wire; BLVV aluminum core PVC insulated PVC sheathed wire; BVR copper-core PVC insulated cord; RV copper core PVC insulated installation cord; RVB copper core PVC insulated flat connecting wire; BVS copper-core PVC insulated stranded wire; RVV copper core PVC insulated PVC sheathed flexible cord; BYR polyethylene insulated cord; Polyethylene insulated PVC sheathed flexible cord; RY polyethylene insulated cord; RYV polyethylene insulated PVC sheathed flexible cord 1 has the advantages of occupying less land.
Generally buried in soil or laid indoors, in ditches and tunnels. The insulation distance between lines is small, there is no iron tower, so it occupies less land and basically does not occupy ground space. 2. High reliability.
Less influenced by climate conditions and surrounding environment, stable transmission performance and high reliability. It has more favorable conditions for the development of ultra-high voltage and large capacity, such as low temperature and superconducting power cables.
4 large distributed capacitance. 5. Less maintenance work.
6 the possibility of electric shock is small. I hope my answer can help you. Thank you for your adoption.
Global wire and cable portal-cable network.
3. Cable TV knowledge
Wire and Cable model specification catalogue plastic insulated power cable 0 RF cable 0 cable cable
Implementation standard of XLPE insulated power cable: the performance of XLPE insulated power cable conforms to GB12706.3-1991,which is equivalent to IEC60502- 1997, and the flame retardant performance conforms to GB12666.5-/kloc-. (Flame-retardant performance requirements are not applicable to non-flame-retardant cables) Usage characteristics: rated working voltage of cable U0/U0.6/1kV; Test voltage (duration ≤ 5min) 3.5kV; Long-term working temperature of cable conductor ≤ 90℃; During short circuit (duration ≤5s), the temperature of cable conductor is ≤ 250℃; When laying cables, the minimum bending radius of single-core cables should be ≥ 20 times of the cable outer diameter, and multi-core cables should be ≥ 15 times of the cable outer diameter; When laying cables, the ambient temperature should be ≥0℃, and if it is lower than 0℃, it should be preheated in advance, and the laying is not limited by the drop.
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4. Electrical and cable knowledge
1, 25 is it copper or aluminum around 25 square meters? Is it hard wire or cable? According to the 32.5kw provided by you, the calculated current I = 32.5/1.732/0.9/0.38 = 55a for long-term use can be calculated. Generally, the cable will be increased by one level according to the circuit breaker. If the YJV or VV national standard cable is 25 square meters, there is absolutely no problem. If the national standard hard conductor of copper is selected (the current carrying capacity is about 80, which is slightly different according to the pipe penetration situation), there should be no problem; 1, about 70 If three central air conditioners are used at the same time, the current is 55*3= 165A, and the current carrying capacity of YJV national standard cable is 209a. The current carrying capacity of VV national standard cable is 179A, and 70m2 is definitely small. At least leave some margin, not to mention the national standard.
5. Cable TV knowledge
Representation method of wire and cable The representation method of wire and cable mainly consists of three parts: model, specification and standard number.
1, the meaning of the model The wire and cable models of electrical equipment and power cables are mainly composed of the following seven parts: Some special wire and cable models have finally derived codes. The following will introduce the meaning of letters in the most commonly used wire and cable models: 1) category, Usage code A- installation wire B- insulated wire C- marine cable K- control cable N- agricultural cable R- flexible wire U- mining cable Y- mobile cable JK- insulated overhead cable M- ZR- flame retardant NH- flame retardant ZA-A flame retardant ZB-B flame retardant ZC-C flame retardant WD- low smoke halogen-free 2) conductor code T- copper conductor (omitted) L. -PVC plastic Sheath code V-PVC sheath Y- polyethylene N- nylon sheath P- copper wire braided shield P2- copper tape shield L- cotton yarn braided waxing gram Q- lead package 5) Characteristic code B- flat R- soft C- heavy Q- light G- high voltage H- S- used for electric welding machine. 2— Double steel strip 3— thin round steel wire 4— thick round steel wire 7) outer sheath code 1— fiber layer 2—PVC sleeve 3—PE sleeve 2, Examples of the most commonly used types of wires and cables for electrical equipment VV-copper core PVC insulated PVC sheathed power cable VLV-aluminum core PVC insulated PVC sheathed power cable YJV 22-copper core XLPE insulated steel belt armored PVC sheathed power cable KVV-PVC insulated PVC sheathed control cable 227IEC 01(BV)-BV for short, Universal single-core hard conductor unsheathed cable 227IEC 02 (RV for short)-RV Universal single-core soft conductor unsheathed cable 227IEC 10 (BVV)-BVV for short is 227IEC 52 (RVV)-RVV for short is 227IEC 53 (RVV). -RVV is abbreviated as ordinary PVC sheathed flexible cord BVR- copper core PVC insulated wire BVR- copper core PVC insulated flexible cable bvvb-- copper core PVC YQW—- light rubber sheathed flexible cable YH-welding machine cable 3. Specifications and specifications consist of rated voltage, number of cores and nominal cross section.
The general rated voltages of wires and control cables are 300/300V, 300/500V and 450/750 V; The rated voltages of medium and low voltage power cables are generally 0.6/ 1kv, 1.8/3kv, 3.6/6kv, 6/6( 10)KV and 8.7/10 (15). The number of cores of wires and cables depends on the actual needs. General power cables have 1, 2, 3, 4 and 5 cores, wires have 1~5 cores, and control cables have 1~6 1 cores.
The nominal cross-section is an approximation of the cross-section of the catheter body. An integer value near the cross section of a conductor is specified in order to achieve the specified DC resistance, which is convenient for memory and unification.
The cross section of unified conductor in China is 0.5, 0.75, 1, 1.5, 2.5, 4, 6, 16, 25, 35, 50, 70, 95,/kloc-0. It should be emphasized here that the nominal cross section of the conductor is not the actual cross section of the conductor. Many actual cross sections of conductors are smaller than the nominal cross section, and some are larger than the nominal cross section.
In the actual production process, as long as the DC resistance of the conductor can meet the specified requirements, it can be said that the cross section of this cable is qualified. 4. standard number most of the wires and cables we produce now have clear standards, and the main purpose is of course to unify design and use.
Here I mainly introduce several wire and cable standard numbers related to the products produced by our company. 1)GB 5023- 1997 PVC insulated cable with rated voltage of 450/750V and below 2)JB 8734- 1998 PVC insulated cable with rated voltage of 450/750V and below 2) GB 5013-/kl. GB/T 12706-2002 rated voltage 1kV to 35kV extruded insulated power cable and its accessories 4)GB/T 9330- 1988 plastic insulated control cable 5. Give an example a) vv-0.6/13 */. T 12706.2-2002 copper-core PVC insulated PVC sheathed power cable, with rated voltage of 0.6/ 1 kV, 3+ 1 core, nominal section of main core of150m2 and section of fourth core of 70mm2.
B) bvvb-450/750V2 *1.5jb8734.2-1998 copper-core PVC insulated PVC sheathed flat cable, with rated voltage of 450/750v, 2 cores, and nominal conductor section of1.5mm2 c) yjlv22-.
4. The main material of the cable is 1, and the copper wire: the copper wire made of electrolytic copper by continuous casting and rolling process is called low oxygen copper wire; Copper wire made by up-drawing method is called oxygen-free copper wire. The oxygen content of low oxygen copper wire is 100~250ppm, the copper content is 99.9~9.95%, and the conductivity is100 ~1%.
The oxygen content of oxygen-free copper wire is 4~20ppm, the copper content is 99.96~9.99%, and the conductivity is 102%. The specific gravity of copper is 8.9g/cm3.
2. Aluminum wire: All aluminum wires used as wires should be annealed and softened. Aluminum wires used for cables generally do not need to be softened.
The resistivity of aluminum for wire and cable is required to reach 0.028264Ω. mm2/m, and the specific gravity of aluminum is 2.703g/cm3. 3. Polyvinyl chloride (PVC): PVC plastic is based on PVC resin and mixed with various additives, such as antioxidants, fillers, brighteners and flame retardants. Its density is about 1.38~ 1.46g/cm3.
The characteristics of PVC material: superior mechanical properties, chemical corrosion resistance, non-flammability, good weather resistance, good electrical insulation and easy processing. Disadvantages of PVC materials: ① There is a lot of toxic smoke when burning; ② Poor thermal aging performance.
PVC can be divided into insulating materials and sheath materials. 4. Polyethylene (PE): Polyethylene is polymerized from refined ethylene and can be divided into low-density polyethylene (LDPE), medium-density polyethylene (MDPE) and high-density poly according to density.
6. Who knows the common sense of wires and cables?
As the main carrier of power transmission, wires and cables are widely used in electrical equipment, lighting lines, household appliances and so on.
Consumers should pay attention to the following points when choosing wires and cables: First, it is recommended to buy brand-name products produced by well-known enterprises. These enterprises have strict quality control over their own products, which guarantees the quality of their products to some extent. Second, pay attention to product identification.
When purchasing wire and cable products, we should observe whether the product certificate completely indicates the product model, specification, rated voltage, number of cores, production date, implementation standard, license number and other related information, and the product surface should be printed with the continuity mark of the factory name, product model and rated voltage to verify whether the relevant information is consistent. Third, check the material of the product.
Pay attention to identify the material of the cable when purchasing, such as whether the insulation and sheath are elastic, whether there are burrs or protrusions on the surface, whether the appearance should be smooth, round and uniform in color; Whether the copper (aluminum) core can meet the requirements, the conductor resistance should be tested when conditions permit. Fourth, pay attention to the length.
There is a length mark on the certificate. You can first estimate the length of a coil of wire in the finished package, and then count the number of coils to see if the length of the wire is "short of two pounds". 5. When selecting wire and cable products, you should consult experienced professional electricians, and use wires with appropriate cross-sectional size and voltage grade according to your own power load.
7. Wire and cable knowledge
There is a lot of knowledge about cables. I don't know what you need.
Provide some basic knowledge of wire and cable and summarize the manufacturing technology of wire and cable. The manufacture of wire and cable is completely different from the production mode of most mechanical and electrical products. Mechanical and electrical products usually adopt the method of assembling another part into a part and assembling multiple parts into a single product, and the products are measured by unit or number.
Wires and cables are based on length. All wires and cables are made of conductors, and insulation, shielding, wiring and protective layers are added layer by layer around the conductors.
The more complex the product structure, the more layers are superimposed. 1. Manufacturing process characteristics of wire and cable products: 1. Long-length continuous superposition combined production mode The influence of long-length continuous superposition combined production mode on wire and cable production is overall and controlling, involving and influencing: (1) Production technology and equipment arrangement All kinds of equipment in the production workshop must be reasonably discharged according to the process flow required by the product, so that the semi-finished products in each stage can flow in an orderly manner.
Equipment configuration should consider different production efficiency and balance production capacity. Some equipment may need to be equipped with two or more units to balance the production capacity of the production line. Therefore, the reasonable selection and combination of equipment and the layout of production sites must be balanced and comprehensively considered according to products and production.
(2) Production organization and management Production organization and management must be scientific, reasonable, thorough, accurate, strict and meticulous, and the operator must operate in strict accordance with the technological requirements. Problems in any link will affect the smooth process and the quality and delivery of products. Especially for multi-core cables, if the length of one pair or basic unit is short, or there are quality problems, the whole cable will be short and scrapped.
On the other hand, if a unit is too long, it must be sawed off, resulting in waste. (3) The production mode of long-length continuous superposition and combination of quality management makes any link in the production process have a little problem instantly, which will affect the quality of the whole cable.
The more inner quality defects, the greater the loss if production is not stopped in time. Because the production of wire and cable is different from the assembled product, it can be disassembled and reassembled and replaced with another one; The quality problem of any part or process of wire and cable is almost irreparable for this kind of cable.
The post-treatment is very negative, either sawing short or degrading, or scrapping the whole cable. It cannot be disassembled and reassembled.
The quality management of wires and cables must run through the whole production process. The quality management inspection department should inspect the whole production process, the operators should conduct self-inspection and mutual inspection between the upper and lower processes, which is an important guarantee and means to ensure product quality and improve the economic benefits of enterprises.
2. Wire and cable manufacturing with many production processes and large logistics involves a wide range of processes, from smelting and pressure processing of non-ferrous metals to chemical technologies such as plastics, rubber and paint; Textile technologies such as wrapping and weaving of fiber materials, wrapping of metal materials and longitudinal wrapping of metal strips, and welding metal forming and processing technology. All kinds of materials used in wire and cable manufacturing are not only of many kinds, varieties and specifications, but also of large quantity.
Therefore, the quantity, spare capacity, batch cycle and batch number of various materials must be approved. At the same time, as an important part of management, we should do a good job in the decomposition, recovery, reuse and waste disposal of waste products, and attach importance to saving.
In wire and cable production, from the import and export and storage of raw materials and various auxiliary materials, to the circulation of semi-finished products in each process, and then to the storage and delivery of products, the logistics volume is large, which must be rationally distributed and dynamically managed. 3. Special equipment Multi-core wire and cable manufacturing adopts special production equipment with the process characteristics of this industry to meet the structural and performance requirements of cable products and meet the requirements of long-length continuous and high-speed production as much as possible, thus forming a series of special equipment for cable manufacturing.
Such as extruder series, wire drawing machine series, stranding machine series, winding machine series and so on. The manufacturing technology of wire and cable is closely related to the development of special equipment and promotes each other.
New technical requirements have promoted the emergence and development of new special equipment; On the other hand, the development of new special equipment promotes the popularization and application of new technologies. Such as wire drawing, annealing and extrusion; Special equipment such as physical foaming production line promotes the development and perfection of wire and cable manufacturing technology, and improves the product quality and production efficiency of cables.
Second, the main process of wire and cable wire and cable are made by three processes: drawing, twisting and coating. The more complex the model and specification, the higher the repeatability. 1. Stretching in metal pressure working. Under the action of external force, the metal is forced to pass through the die (press wheel), and the cross-sectional area of the metal is compressed to obtain the required cross-sectional area shape and size. This technical processing method is called metal drawing.
The drawing process is divided into monofilament drawing and stranded drawing. 2. Stranding In order to improve the flexibility and integrity of wires and cables, more than two single strands are intertwined in the specified direction, which is called stranding.
The twisting process is divided into conductor twisting, cabling, weaving, steel wire armoring and winding. 3. Cladding According to the different performance requirements of wires and cables, special equipment is used to cover different materials outside the conductor.
The coating process is divided into: a. Extrusion: rubber, plastic, lead, aluminum and other materials. B. longitudinal packaging: rubber and corrugated aluminum strip materials.
C wrapping: ribbon paper tape, mica tape, alkali-free glass fiber tape, non-woven fabric, plastic tape, linear cotton yarn, silk and other fiber materials. D. dip coating: insulating paint, asphalt, etc. Three. Basic process flow of plastic wire and cable manufacturing 1. Copper-aluminum monofilaments are used to draw copper-aluminum rods commonly used in wires and cables. At room temperature, the wire drawing machine is used to pass through one or more die holes of the wire drawing die, so that the cross section is reduced, the length is increased and the strength is improved.
Wire drawing is the first process of wire and cable enterprises, and the main technological parameter of wire drawing is die matching technology. 2. Monofilament annealed copper-aluminum monofilaments are heated to a certain temperature, and the toughness is improved and the strength of monofilaments is reduced by recrystallization to meet the requirements of wires and cables for conductive cores.
The key of annealing process is to prevent copper wire from oxidation. 3. Stranding of Conductors In order to improve the flexibility of wires and cables and facilitate laying and installation, the conductive wire core is twisted by multiple monofilaments. According to the stranded form of conductive wire core, it can be divided into regular stranded and irregular stranded.
Irregular twisting is divided into bundle twisting and concentric double twisting.
8. Who knows the common sense of wires and cables?
As the main carrier of power transmission, wires and cables are widely used in electrical equipment, lighting lines, household appliances and so on. Consumers should pay attention to the following points when choosing wires and cables:
First, it is recommended to buy brand-name products produced by well-known enterprises. These enterprises have strict quality control over their own products, which guarantees the quality of their products to some extent.
Second, pay attention to product identification. When purchasing wire and cable products, we should observe whether the product certificate completely indicates the product model, specification, rated voltage, number of cores, production date, implementation standard, license number and other related information, and the product surface should be printed with the continuity mark of the factory name, product model and rated voltage to verify whether the relevant information is consistent.
Third, check the material of the product. Pay attention to identify the material of the cable when purchasing, such as whether the insulation and sheath are elastic, whether there are burrs or protrusions on the surface, whether the appearance should be smooth, round and uniform in color; Whether the copper (aluminum) core can meet the requirements, the conductor resistance should be tested when conditions permit.
Fourth, pay attention to the length. There is a length mark on the certificate. You can first estimate the length of a coil of wire in the finished package, and then count the number of coils to see if the length of the wire is "short of two pounds".
5. When selecting wire and cable products, you should consult experienced professional electricians, and use wires with appropriate cross-sectional size and voltage grade according to your own power load.
9. Knowledge about cables
The spare core in the cable usually refers to the control cable! Because there are many problems in the control part! This is convenient for future modification and maintenance, and the cost is not much! But in the main circuit you mentioned, standby cables are generally not considered, mainly considering the importance of equipment and the relationship between installation and cost. If you want to add it, just pack it according to the same thread! Voltage drop is generally caused by long circuit lines and large current of equipment, and it is also caused by line aging and leakage, but it is a minority after all. The solution is 1. Minimize multiple lines. 2. Motor equipment shall adopt soft start as far as possible (such as star delta, frequency converter and step-down starting resistor, etc.). ). 3. Install power capacitor compensation at the equipment end (this is the main solution), but it is best to start and stop together with the motor for good calculation.