Abstract
The contents
- introduction
- 1. The characteristics of the cable
- 2. Design cables
- 3. Sources of scrap cable and wire products
- The list of sources
introduction
Quite difficult to imagine modern society without costing electricity. With the advent of electrical appliances, our lives became more convenient and comfortable. Today, electricity is a necessity, without which people cannot exist. To ensure that the electricity functioned for the benefit of mankind, for many years we developed a huge number of various accessories. Among them the important place occupied by the conductors of electrical energy, the most common of which is the cables and wires. Each cable has a specific function and has its purpose. Cable is a device used to transfer electric energy. The cable consists of one or more isolated from other conductors. Each of them is equipped with a hermetic protective sheath of plastic, rubber, aluminium or lead. Cable, for example, power used for transmission and distribution of electrical energy in the lighting and power installations. And, for example, the control cable is used to create control circuits and alarms. In a separate group communication cables, optical cables, telecommunication cables. By types of protection are divided into armored cables that are over protective sheath armored with steel tapes or wire, and naked, if the protective sheath of the cable does not have a jute impregnation. All cable products can be divided into several types: Copper cable – type cable conductors, the core of which is made of copper. Cable, copper, as a rule, performs the functions of a power cable. Copper cable characterized by enhanced durability and is fire-resistant.
1. The characteristics of the cable
The material core
In a domestic environment the most commonly used aluminum, copper and alumold. The first two all clear, but what is alumold? It's not the alloy, as one might think at first, because of the heavy and light metals combine very badly, and a composite material consisting of an aluminum core and topped with a layer of copper. Why combine these two materials, it will be clear after consideration of their properties.
Aluminium — a great material: light, cheap, has good conductivity, gives good heat and chemical resistant. However, there are several "but" substantially podrachivaya reputation of this metal.
1. Aluminum wire may not be flexible. Remember how good break in two a wire of this material, if you bend it a few times. The conclusion is simple — this wire is used only in fixed installations where there are no acute angles of twist of the cable while laying.
2. Aluminium oxidises in air. Aluminium oxide — refractory film of dark color formed on the metal surface and which is dielectric. At the points of contact can seriously hinder the flow of electric current. Hence, excessive overheating, and the risk of losing contact in the joints. 3. Aluminium is a very good conductor, but only in the case that does not contain impurities, which make very difficult. Compared to copper this metal has a conductivity of less half.
3. Aluminium is a very good conductor, but only in the case that does not contain impurities, which make very difficult. Compared to copper this metal has a conductivity of less half.
Copper, along with its many advantages has fewer drawbacks. Advantages: conductivity is higher than that of aluminium, the flexibility, does not form an oxide film. From flexibility depends on the thickness of the veins. Aluminum cables can be thinner than 2.5 mm, and copper can be made of wires 0.3 mm thick?. Disadvantages: high cost, high density, and hence weight, of the impossibility of a direct connection to aluminum conductors. Upon contact of these two metals form a galvanic couple and the resulting currents destroy the contact. Therefore, if necessary, contact using special terminal connections. Alumold — mechanical composite consisting of an aluminum core and a copper shirt, which is 10 % of the volume of the core. Combines the positive qualities of aluminium and copper. Cons: in all respects inferior to the conductors of the individual metals. Plus: low cost. Conductor cross-section Wires and cables are produced with a cross section of the core from 0.3 mm to 800?. In the home, such extreme values are not used. Extreme performance for home — they are guides with a section of tendon from 0.35 to 16 mm, rare — 25 mm. First of all, the thickness of the core depends on the voltage and amperage. Dependence is simple: the greater the ratio, the higher the current load. The calculation of the required sections depending on the load produced by complicated formulas, so all data for this question are shown in the table below.
2. Design cables Coal mine cable For multiple strip mines developed a special semi-flexible cables with insulation and sheath from polivinilo-ridnyi plastic stamps EVT on voltage 660 and 6 000 V AC. The cable has three main conductor (cross-section 10-95 mm2 ), one grounding (10 mm2 ) and two to four auxiliary cores (2.5 and 4 mm d ). Conductive cores are made of copper stranded (type II). The main and auxiliary cores of isolated PVC plastic.
Use uninsulated grounding mine. Over insulation of main conductors is applied to the screen of semi-conductive of PVC or copper tape. Auxiliary leads are twisted around the core made of PVC and wrapped with copper tape. Main cores and pre-made auxiliary leads are twisted around the grounding conductor and insulation applied waist. Then placing the armor – seven wire rope of galvanized steel wire with a diameter of at least 0.4 mm and a shell of plastic polusrednego. To simplify the cable construction it is possible to replace the seven wire ropes, galvanized round steel wire.
For supply of mobile transformer substations of district developed a special cable for voltage 6000 in brand CSPN. This cable has three main, one ground and two auxiliary cores. The main current-conducting core made of a cross section of 25, 35 and 50 mm2 , and grounding and auxiliary leads - at 10 mm g . Main cores isolated rubber with a thickness of 5.6 mm, AUX - 2 mm thick; on top place a layer of semi-conductive rubber with a thickness of 0.5-1.0 mm, wrapped with rubberized fabric tape and braid of tinned copper wire with diameter of 0.3 mm with a density of at least 90%. The insulation for auxiliary conductors is applied a layer of semi-conductive rubber with a thickness of 1.7 mm. Earthing cover mine semi-conductive rubber with a thickness of 3.4 mm.
Isolated main, auxiliary and grounding conductor are twisted around the core of rubber and put a rubber sheath based on polychloroprene rubber with a thickness of 8 mm.
Mining flexible cables are intended for connection of mobile machines and mechanisms to the network AC voltage of 660 V. the Cables are intended for operation at ambient temperatures from -30 to +50° C. permissible working temperatures on the veins +66° C. the Conductive cores of the cables HRSA twist of wires in strands and strands in the vein in the same direction (type III). Stranding of the main cores and control cores are produced in the left direction, and the lived ground - in the right direction. The main conductors of isolated rubber thickness 1.6-2.2 mm overlay them on top of a semiconducting layer with a minimum thickness of 0.3 mm. shielding of main conductors in these cables are used to ensure work safety in coal mines. Screens connected to the system cable protection, which disconnects the cable at the damage of its shell. Mine ground cover semi-conductive rubber. Control cores are isolated by rubber thickness of 1.0 mm. Main cores and control cores have different colors or markings. Shielded main cores and control cores twisted around the conductor in increments of no more than 10 D. the Direction of lay - right.
Twisted core is applied a strip of polyethylene terephthalate, polyamide or other synthetic tape and a sheath of rubber based on polychloroprene rubber with a thickness of 4-5 mm. Cables are made with three main conductors cross-section 4-70 mm2 one conductor cross section 2.5-10 mm2(depending on the section of main conductors) cores and three control sections 1.5-4.0mm2 (depending on section of main conductors). In mine the cables when tested on the mechanical, durability to deformations of bending and torsion main cores utterance 4-16mm2 can withstand at least 3,000 cycles, and the core cross-section 16-70 mm2 - not less than 2000 cycles.
Firm Bronco (USA) such cables are manufactured with insulation on the basis of butyl rubber, ensuring the permissible operating temperature to 85° C. Over laid in the same plane as the reinforcing cores impose rare (one thread in pasme) the braiding of the cord and the shell of the rubber based on polychloroprene rubber with a content of at least 67,32%. Two-, three - and four-core cables working with the periodic winding and a winding on it, this company produces with cores twisted into cable with a filling of fibrous material, over which is applied a rare braid of the cord (in one thread) to harden the shell of sharp with the contents of neoprene 67,32%. For (attachment drilling and other hand tool to the AC mains with a nominal voltage up to 127 V at ambient temperature from -30 to +50°C release shielded cables brand SRBA and unshielded SHRB (GOST 10695-63).
A conductor cross section of 1.5, 2.5 and 4 mm2 made from wires with a diameter of 0.20 mm and a cross section of 6 mm2 - wires with a diameter of 0.26 mm.
Stranding of wires in strand and strands in the vein produce one (left) side, with the exception of the grounding conductor, the direction of lay of which is right. The step of lay of strands is not more than 16 D, and the strands in the cable is not more than 14 D. stranding of the strands of the grounding conductor is produced around a core of cotton or other material in increments not more than 5D. Conductive core, with the exception of the ground to insulate the rubber thickness of 1.0 mm, wherein for each conductor by color or marking. To ensure work safety in coal mines over insulation of main and auxiliary conductors of the cable is applied to the screen of semi-conductive rubber with a thickness of 0.7 mm. Three main and subsidiary strands are twisted in the right direction around an uninsulated grounding conductor with a pitch of not more than 3.5 D and put a sheath of oil-resistant rubber, not spreading burning, thickness 2.5-3.5 mm depending on the diameter of the cable. Samples of cable tested in a mechanical strength to the deformations of bending and torsion, which must be at least 22,000 cycles to composite cable cross-section 1,5 and 2,5 mm and 15000 cycles for composite cable cross-section 4 and 6 mm2 .
located cable a Fundamentally new qualitative leap in the technology of communication bands occurred with the appearance of optical cables. In the first half of 1980-ies was carried out gasket OK for regular use of the line length from 300 to 10,000 km at depths of up to 7500 m. The damping coefficient of cables with single-mode fibers at a wavelength of 1.3 µm was 1 dB/km, the length of the regeneration area – 35 km. In 1985 it was laid the first deep-sea optic cable connection large capacity between the two Canary Islands (OK, first generation). This deep-water system contains several regenerators, the transmission speed was 280 Mbps for 2 S, the transfer was carried out at the wavelength of 1.3 µm. Currently, undersea fiber optic cables have a length of more than 300000 km and it connects 90 countries. Launched in 1988 the line of the Transatlantic TAT-8 between the United States, France and England, he also worked at the wavelength of 1.3 µm and provided a capacity of 280 Mbit/s for 2 S. Up to this point 65% of all international channels between the US and Europe provided by satellite.
Currently, more than 75% of all channels is provided by means of OK. A few months after the introduction of TAT-8 was launched a TRANS-Pacific line of TRS-3, connecting the United States and Japan. The second generation OK also used the regenerators, but was already working at the wavelength of 1.55 µm and transmission rate of 560 Mbit/s for 2 S. To this generation include TAT-9 (USA – Canada – England-France – Spain), TAT-10 (USA – Germany), TAT-11 (USA – England – France) and TRS-4 (USA – Canada – Japan). TAT-9 was provided by electronic multiplexing and de-multiplexing in the underwater part of the system. The third generation OK (1995) provided the initial segment of the first transoceanic ring system of TAT-12, TAT-13 and TPC-5. For a couple of S ensures the speed of 5 Gbit/s synchronous digital hierarchy, used erbium-doped amplifiers for optical signals and the wavelength is 1.55 µm. The fourth generation of OK allowed to use the systems that provide direct amplification of optical signals.
The forecast of growth of volumes of transmission of information long-distance communication notes that the capacity and transfer speed doubles every two years. Underwater OK must have high tensile strength and can withstand water pressure up to 75 MPa. When designing underwater OK we have to consider requirements such as flexibility, resistance to storm, necessary when laying on the bottom and the extraction directly from the bottom and from the trench to Bonham suspension repair; the ease and speed of repair.
Be aware that the cost of the OK is a significant part of the cost of the entire system. Cable design for submarine system depends on the place of their laying. There are: deep-water cables, with protection against significant hydrostatic pressure; cables for installation in shallow areas protected from the chains and anchors; cables for the coastal strip with high mechanical protection and cables for laying in ground, trenches to a junction point for connection to ground network.
In the manufacture of cable do I need to achieve low residual stresses in the CQ. Currently, the best examples of it is 0.05% of the allowable. S very sensitive to the effects of sea water. In the repair line you want to remove the pieces OK, which discovered traces of water. If you have a constant hydrostatic pressure the rate of penetration of water along the cable is constant, but can be reduced through the use of hydrophobic fill. The structure of the filler should be such that it infiltrated all the voids inside OK, without affecting S and effectively sealing the cable in the longitudinal direction. Another problem is the appearance of the inside cable of hydrogen, which has a negative effect on OS. The hydrogen can be released due to the interaction of the materials from which is made OK, with sea water. Recent studies have demonstrated that the smallest influence of hydrogen on S is achieved by metallization of the fiber surface. Started research triaxial construction S which also enhances its resistance to hydrogen.
To reduce the influence of hydrostatic pressure on S by using the design of the cable is a hollow tube which may be made of metal and bears the function of the conductor.
The tube cross section, and its size is often determined not by the pressure, and the requirement for the transmitted electric power. Up quite often made of copper or aluminum. In addition to this method, protection from hydrostatic pressure can be realized by the use of twisting the steel wires that form a solid construction.
Reinforcing steel elements must ensure the durability not only by static but also dynamic loads. When a two-layer arrangement of the wires (the direction of lay of the wires in opposite layers) achieve a neutralization of the torques and eliminate the possibility of occurrence of loops. In gives the design and characteristics of submarine OK for different operating conditions and depths of water bodies foreign companies and JSC "Sevcable-optic", Saint-Petersburg. It should be noted that the issue of deep-sea OK starting to be carried out by domestic manufacturers. So, the specialists of JSC "Sevcable-optic" fiber optic cables designed for underwater marine strip to a depth of 400 m to 1000 m. The cable is an axial design in the center of which is an optical module in the form of a sealed tube made of stainless steel with a freely positioned optical fibers. On top of the module layer is copper conductors for remote power supply.
This is followed by an intermediate plastic sheath and the outer integument consisting of broniovius steel wires and polyethylene outer sheath. the design of the underwater OK to strip to a depth of 400 m stamps POK-400.
3. Sources of scrap cable and wire products
Scrap and wastes of cable products occupy a considerable share in the total volume of harvesting and processing aluminium and copper scrap. Training of this group of raw materials to recycling requires the use of special technologies and special equipment. Recycling of cable scrap can be divided into several areas depending on the types of cable to be recycled. Processing armored cable One of the ways — the use of shredders, which is ground cable and using magnetic separation to separate the magnetic fraction.
In the presence of aluminum or lead armor required additional separator, which makes it possible to separate fractions of non-ferrous metals. The main advantage of this method is performance, which depends on the type and capacity of the shredder. An alternative could be cutting armored cable on one of the two types of special machines. The first type of machine operates as follows. Idlers grab the cable and bring it to a sharp wedge on top. The depth of the opening is determined by the thickness of the armor. The principle is similar to principle of operation of the plow when plowing. Only in this case "plough" still.
Wound on steel cable insulation can be removed using another type of machine. With the help of special gear wheels twisted steel armor with piece of cable with a length of about 1.5 m. This machine can also be used for pulling out the steel wires from the air lived. These two machines have the obvious advantage over Schroeder: this is the price and the cost of consumed electricity and the cutting of the material without crushing it. Processing non-armoured cable with outer diameter of more than 10-15 mm In case, if the external diameter of cable to be recycled exceeds 10-15 mm, it is better to use machines with rotary knives. These machines feature an easy setting of the machine for any size of cable; high durability of the knives, since the round knife cuts the cable the entire circumference.
In the design of these strippers used the following principle: 10-12 rotating circular knives of different diameters arranged on the same shaft. Diameter of cable to be recycled from 1.5 to 110 mm. these machines can be to cut the cable with plastic, lead, paper and rubber insulation. Machines for cutting cable can also be used to remove the top belt isolation with multi-sector cable, to split it into smaller pieces (bundles of wires) which are then appropriate to recycle method of grinding and separation. Processing of the cable without armor and with an outside diameter of less than 10-15 mm, depending on the volume and type of recyclable material it is recommended to use units with different performance and different ways of separation of the crushed material (air or water). The operating principle is quite simple.
It is necessary that the cable previously cut into pieces with length from 500 to 1000 mm or reeled into bundles with a maximum diameter of 500 mm. During grinding in the cutting mill the material enters between the blades of the rapidly rotating rotor blades and stationary stator. At the same time there is a grinding of non-ferrous metal and separating from the plastic covering. After grinding the crushed mass is sucked off from the grinder and air flow into the cyclone and farther to the table of separation. During separation on the air table separation of mixed fractions of non-ferrous metal and plastic are moved on the inclined screen. Using vibration sieve and uniform cooling of the material by air jets mixed fractions change into a fluid state. Heavier particles are transported by the traffic flow up the working screen into the container for metal. Lighter particles flow down into the container for plastic.
Separation of metallic particles from non-metallic components on the table of water separation occurs due to the different density of materials and, as a result, different behaviour of the materials during separation. Using injector onto a vibrating table supplied with water. The metal particles move upwards in the table, and a plastic float and get washed away to the bottom of the table. This ensures almost 100% separation of materials, regardless of the structure of metal particles. But since the output is a finished product with high moisture content, wet separation, it is advisable to use only when in the processing of the source material in other ways inevitable losses (for example, when processing a copper cable with a core diameter of less than 0.2 mm or cable with aluminum foil). To increase productivity of the line can equip them with shredder pre-shredding. Pre-shredded (30-40 mm) the material is uniformly fed into the mill by belt conveyor. These 2 factors, namely pre-grinding and uniform supply provides increased efficiency by 50-60%.
Preparation of the cable to the processing of Any of the above tools and any of the installations involve the use in the processing of cable, pre-cut into pieces. For machines it is usually chunks up to 1.5 m, for installations (if not provided the preliminary shredding of the shredder) — 0,5-1 m. Cut the cable into pieces by using a hydraulic shear. Packaging After cutting the cable on the machines, it is recommended to compress aluminum and copper wires. This will ensure compact storage and transport in the form of press kits .