English entry name: plug-in bus
Also known as protective, closed and intensive insulated bus' is made up of steel or aluminum bus, protective shell is gold screen, and wiring is assembled according to a certain module combination. You can use incoming and outgoing broadcast connection boxes (equipped with automatic switches) and socket boxes connected with bus bushings for power distribution. Mainly used in machine tool intensive workshops, crystal production workshops, face detection rooms, high-rise civil buildings, auto production line and other places.
Bus bar:
Connect the conductor of the cut-off branch circuit in the electrical equipment. It is the carrier for collecting and distributing electricity, also called bus bar. It is customary to call the conductor of the current-carrying branch circuit in each power distribution device a bus. The function of bus is to collect, distribute and transmit electric energy. Because there is huge electric energy passing through the bus in operation, it bears huge heating and electrodynamics effect when it is short-circuited. Therefore, the bus material, cross-sectional shape and cross-sectional area must be reasonably selected to meet the requirements of safe and economic operation.
The types of buses are hard cars and soft cars. Hard bus bars are made of copper or aluminum and have several shapes, such as rectangle, trough and tube. Most of them are used for indoor power distribution devices of 35 kV and below, and sometimes aluminum tube buses are used for outdoor power distribution devices of 1 10 kV ~ 220 kV. Commonly used flexible buses include aluminum stranded wire, copper stranded wire or steel-cored copper wire. Flexible bus is mostly used for outdoor power distribution devices above 35 kv.
Selection and Application of Busbars Under different environmental conditions, buses of different types and materials should be considered. In addition, for various buses, the bus section should usually be selected according to the maximum long-term working current. Check the short-term thermal stability and dynamic stability of the bus according to the maximum short-circuit current.
Due to the influence of conductor resistance and alternating current trend effect when multiple conductors approach, the bus will generate heat when passing through the current. The allowable heating temperature of bare copper-aluminum bus is 70℃ when it works for a long time, but when the contact surface has reliable tin coating (such as ultrasonic tin lining, etc.). ), the allowable temperature can be increased to 85℃. Limited by the allowable temperature of continuous heating, the long-term allowable current values corresponding to buses with different materials and different sections are given. When selecting a bus section, the actual maximum long-term working current of the bus (considering overload for more than half an hour) should be less than the long-term allowable current value of the selected bus section. In the case of large annual load and large conductors and buses (such as buses of outdoor distribution equipment), buses are usually selected according to the economic current density method. Economic current density is the current flowing through the unit cross-sectional area of the bus when the bus loss, annual maintenance and depreciation expenses of the bus and ancillary equipment are considered to be the lowest. Divide the economic current density by the long-term working current without considering artificial overload, and get the bus section. The bus section selected by the economic current density method is generally larger than that selected by the maximum long-term working current method.
When the bus is thermally stable and short-circuited, a large amount of heat generated in the conductor cannot be dissipated into the surrounding air, which makes the temperature of the conductor rise rapidly. Because of the short duration of short circuit, its allowable temperature is much higher than that when heating for a long time. The allowable heating temperatures of bare copper bus and aluminum bus are 300℃ and 200℃ respectively. When selecting the bus, the short-time heating temperature calculated during the short-circuit transient process of the bus should be less than the above-mentioned short-time heating allowable temperature of the actual bus.
When the dynamic stability of the bus is short-circuited, a great impulse current will flow in the bus, resulting in a great electromotive force. When the mechanical strength of bus and post insulators is not enough, deformation or damage accidents will occur. For three-phase buses arranged in the same plane, when the three-phase buses are symmetrically short-circuited, the electromotive force of the middle phase is the largest, and the maximum electromotive force of the short-circuit appears in several 0.0 1 after the short-circuit. Therefore, the dynamic stability of the bus is usually checked according to the three-phase short circuit. Under the action of this maximum electromotive force, the maximum stress of the bus should be less than the allowable stress value of the bus material.
Measures to increase bus stability ① reduce the distance between the supporting insulators of the same phase bus; ② Increase the distance between buses; ③ Limit short-circuit current.
Busbars are divided into hard buses and soft buses according to the structure. Hard bus is divided into rectangular bus and tubular bus.
Rectangular bus is generally used from the main transformer to the distribution room. Its advantages are convenient construction and installation, small operation change, large current carrying capacity, but high cost.
Flexible bus is used outdoors. Because of the large space, the wires will swing, which will not cause insufficient wire spacing. Flexible bus has simple structure and low cost.
Cable:
Wires and cables refer to materials used for power, communication and related transmission purposes. There is no strict boundary between "wire" and "cable". Usually, products with few cores, small product diameter and simple structure are called wires, those without insulation are called bare wires, and others are called cables; A conductor with a larger cross-sectional area (greater than 6 square millimeters) is called a large conductor, a conductor with a smaller cross-sectional area (less than or equal to 6 square millimeters) is called a small conductor, and an insulated wire is also called a distribution wire.
Wires and cables mainly include bare wires, electromagnetic wires and insulated wires, power cables, communication cables and optical cables for electrical appliances.
Nomenclature of wires and cables
The complete naming of wires and cables is usually complicated, so people sometimes replace the complete name with a simple name (usually the name of a category) combined with model specifications. For example, "low voltage cable" represents all plastic insulated power cables of 0.6/ 1kV class. The type spectrum of wires and cables is relatively perfect. It can be said that as long as the standard model specifications of wires and cables are written, a specific product can be defined, but what is its complete name?
The naming of wire and cable products has the following principles:
1. What is included in the product name.
(1) Product application name or size grade
(2) Material or type of product structure;
(3) Important features or additional features of the product
Basically, they are all named in the above order. Sometimes, in order to emphasize important or additional features, features are written before or before the corresponding structural description.
2, the order of the structure description
The product structure is described according to the principle from the inside out: conductor-> conductor; Insulation->; Inner sheath->; External sheath->; Armor type.
Step 3 simplify
In order not to cause confusion, some structural descriptions are omitted or abbreviated. For example, aluminum conductors are not allowed to be used in automobile wires and flexible cords, so conductor materials are not described.
Case:
Rated voltage 8.7/ 15kV flame retardant copper core XLPE insulated steel belt armored PVC sheathed power cable.
(It's too long! )
"Rated voltage 8.7/15kV"-application/voltage level
"Flame-retardant"-the characteristic of emphasis
"copper core"-conductor material
"XLPE insulation"-insulating material
"Steel Strip Armor"-material and type of armor layer (double steel strip gap packaging)
"PVC sheath"-inner and outer sheath materials (the inner sheath material is omitted).
"Power cable"-the general name of products.
The corresponding model is written as ZR-YJV22-8.7/ 15, and the model description is as follows.
model
The model composition and sequence of wires and cables are as follows:
[1: category and use ][2: conductor ][3: insulation ][4: inner sheath ][5: structural features ][6: outer sheath or derivative ]-[7: use features]
Items 1-5 and 7 are represented by pinyin letters, and polymer materials are represented by English initials, and each item can be 1-2 letters; Item 6 is the number of 1-3.
Ellipsis principle in the model: copper is the main conductor material used in wire and cable products, so the copper core code T is omitted, except bare wire and bare conductor products. Bare wires and bare conductor products, power cables and electromagnetic wires are not marked with large-scale codes, and wires and cables for electrical equipment and communication cables are not marked with large-scale codes, only small-scale or series codes are listed.
Item 7 is the identification of various special use occasions or additional special use requirements, which is marked with pinyin letters after "-". Sometimes in order to highlight this item, write this item at the front. Such as ZR- (flame retardant), NH- (flame retardant), WDZ- (low smoke and no halogen, enterprise standard), -TH (used in hot and humid areas), FY- (termite prevention, enterprise standard) and so on.
Numerically mark the outer layer or sheath of armor layer.
0 None-
1 Interlocked armored fiber outer quilt
2 PVC sheath with double steel belts
3 thin round steel wire polyethylene sheath
4 thick round steel wire
5 corrugated (embossed) steel strip
6 Double aluminum (or aluminum alloy) adhesive tape
8 copper wire weaving
9 steel wire weaving
The applications of wires and cables are mainly divided into three categories.
1, power system
The wire and cable products used in the power system mainly include overhead bare wires, buses (bus bars), power cables (plastic cables, oil-paper power cables (basically replaced by plastic power cables), rubber cables and overhead insulated cables), branch cables (replacing some buses), electromagnetic wires and wires and cables for electrical equipment.
2. Information transmission system
The wires and cables used in the information transmission system mainly include local telephone cables, television cables, electronic cables, radio frequency cables, optical cables, data cables, electromagnetic cables, power communication or other composite cables.
3, mechanical equipment, instrument system
This part is applicable to almost all other products except overhead bare wires, but mainly power cables, electromagnetic wires, data cables, instrument cables and so on.
Wire and cable products are mainly divided into five categories.
1, bare wire and bare conductor products
The main characteristics of this kind of products are: pure conductor metal, without insulation and sheath, such as steel-core aluminum stranded wire, copper-aluminum bus, electric locomotive wire and so on. The processing technology is mainly pressure processing, such as melting, calendering, stretching, twisting/compression twisting, etc. Products are mainly used in suburbs, rural areas, main lines of users, switch cabinets and so on.
2. Power cable
The main characteristics of this kind of products are: extruding (winding) insulation layer outside the conductor, such as overhead insulated cable, or multi-core stranded (corresponding to phase, neutral and ground wires of power system), such as overhead insulated cable with more than two cores, or adding sheath layer, such as plastic/rubber sheathed wire and cable. The main technologies include drawing, winding, insulation extrusion (winding), cabling, armoring, sheath extrusion and so on. There are some differences in different process combinations of various products.
Products are mainly used for the transmission of high-voltage electric energy in power generation, distribution, transmission, substation and power supply lines, with large current (tens of amperes to thousands of amperes) and high voltage (220V to 500kV and above).
3. Wires and cables for electrical equipment
The main characteristics of this kind of products are: many varieties and specifications, wide application range, and the application voltage is mostly 1kV and below. Facing special occasions, new products are constantly derived, such as fire-resistant cables, flame-retardant cables, wdz/wdz, termite-proof cables, rat-proof cables, oil-resistant/cold-resistant/temperature-resistant/wear-resistant cables, medical/agricultural/mining cables, thin-walled wires and so on.
4. Communication cables and optical fibers (introduction)
In the past twenty years, with the rapid development of communication industry, products have also developed at an amazing speed. From 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.
This kind of products usually have small and uniform structural dimensions and require high manufacturing accuracy.
5. Electromagnetic wire (winding wire)
Mainly used in various motors, instruments and meters, etc.
A derivative/new product of wire and cable
Derivative/new products of wires and cables are mainly produced due to different application occasions, application requirements, equipment convenience and equipment cost reduction, adopting new and special materials, changing product structure, improving process requirements, or combining different kinds of products.
Use different materials such as flame retardant cable, wdz, termite-proof cable, rat-proof cable, oil/cold/temperature resistant cable, etc.
Change the product structure, such as fire-resistant cables;
Improve the technological requirements of medical cables;
Combined products such as OPGW；;
Convenient installation, reducing the cost of equipment, such as prefabricated branch cables.
Classification of cables and wires
1. What are the common wires and cables? Answer: According to the purpose, it can be divided into bare wire, insulated wire, heat-resistant wire, shielded wire, power cable, control cable, communication cable and radio frequency cable.
2. What kinds of insulated wires are there? Answer: There are the following kinds of insulated wires: PVC insulated wire, PVC insulated cord, NBR-PVC mixed insulated cord, rubber insulated wire, plastic insulated wire with aluminum core buried directly in agricultural land, rubber insulated cotton yarn textile cord, PVC insulated nylon sheathed wire, and PVC insulated cord for power and lighting.
3. Where is the cable tray suitable? Answer: Cable tray is suitable for laying power cables and control cables indoors and outdoors in general industrial and mining enterprises, and can also be used for indoor and outdoor erection in telecommunications and radio and television departments.
4. What are the cable accessories? Answer: Common electrical accessories include cable terminal junction box, cable intermediate junction box, connecting pipe and terminal, steel plate junction box, cable bridge, etc.
5. What is a cable intermediate joint? Answer: The device that connects the conductor, insulation shield and protective layer of the cable to connect the cable is called the cable intermediate joint.
The cable model consists of eight parts:
1. Use code-not marked as power cable, k as control cable and p as signal cable;
Insulation code -Z oil-immersed paper, X rubber, V PVC, YJ crosslinked polyethylene.
Third, the conductor material code-not marked as copper, L is aluminum;
Four. Inner sheath code -q lead sheath, L aluminum sheath, H rubber sheath, V PVC sheath.
Verb (abbreviation of verb) derives the code -D does not drip, P is dry and insulated;
Six, the outer sheath code
Seven, specialty code-TH humid tropical zone, TA dry tropical zone;
Eight, rated voltage-unit KV
Questions about cable models
1, SYV: solid polyethylene insulated RF coaxial cable
2. SYWV (Y): Physical foamed polyethylene insulated cable for CATV system, and video (radio frequency) coaxial cables (SYV, SYWV, SYFV) are suitable for closed-circuit monitoring and CATV engineering.
Special cable structure for SYWV(Y), SYKV CATV and broadband network: (coaxial cable) single oxygen-free round copper wire+physical foamed polyethylene (insulation)+(tin wire+aluminum)+polyvinyl chloride (polyethylene).
3. Signal control cables (RVV sheath line and RVVP shielded wires) are suitable for building intercom, burglar alarm, fire fighting, automatic meter reading and other projects.
RVVP: Copper conductor PVC insulated shielded PVC sheathed flexible cable voltage 300V/300V 2-24 cores.
Uses: Instruments, meters, intercom, monitoring installation.
4.RG: Physical foamed polyethylene insulated access network cable is used to transmit data analog signals in coaxial optical fiber hybrid network (HFC).
5.KVVP: PVC sheathed braided shielded cable uses: signal transmission, control and measurement of electrical appliances, instruments and distribution devices.
6.RVV(227IEC52/53) PVC insulated flexible cable uses: household appliances, small power tools, instrumentation and dynamic lighting.
7. Flexible cable for installing AVVR PVC sheath
8.SBVV HYA data communication cables (indoor and outdoor) are used for telephone communication, connection of radio equipment and wiring of telephone distribution network junction boxes.
9.RV and RVP PVC insulated cables
10, RVS and RVB are suitable for connecting cables of household appliances, small electric tools, instruments, meters and power lighting.
1 1, BV, BVR PVC insulated cable uses: suitable for fixed wiring of electrical instruments and power lighting.
12, Ribbed Speaker Connection Line (Heating Line)
13, KVV PVC insulated control cable uses: signal transmission, control and measurement of electrical appliances, instruments and power distribution devices.
14, SFTP twisted-pair transmission telephone, data and information network
15, UL2464 computer connection cable
16, VGA monitor cable
17, SYV coaxial cable wireless communication, broadcasting, monitoring system engineering and related electronic equipment for transmitting RF signals (including integrated coaxial cable)
Coaxial cable for elevator 18, SDFAVP, SDFAVVP, SYFPY.
19, JVPV, JVVP, JVVP copper core PVC insulated and sheathed copper wire braided computer control cable