Cable Industry
Kablo SanayiiA cable is a metallic conductive wire covered with an insulating material used to transmit electric current. One or more wires are covered with an insulating material. The conductors can be a single wire of copper or aluminum or a plaited wire made of finer wires. It requires aluminum wires to be 1/2 diameter larger than copper to carry the same amount of current. Therefore, copper cable is used in places with space problems. Aluminum is mainly preferred for airborne lines that are not too heavy. If the cables are desired to be stronger, they are strengthened with steel braids. They are mainly used on long lines that pass high in the air, such as high voltage lines around the country. The strength required from the cable is related to carrying both its own weight and, in addition, the weight of the ice that will freeze or the snow that will fall on it. In addition, the tension caused by the wind must be taken into account in the determination of this force.
Cables used underground
Underground cables are always exposed to excessive moisture as they are laid with a duct system. They are usually enclosed in a lead enclosure and classified as multi- or single-conductor according to the number of separately insulated conductors within it. Single-conductor cables are used in high voltage circuits that require large diameter cables. In this case, more than one cable cannot be laid in the duct. Therefore, solid single-conductor cables are laid in separate ducts. Multi-conductor cables are used to distribute electrical energy at relatively low voltage. They can be placed in a single channel. Their costs are low. But their current carrying capacity is limited. Basically, three types of insulators are used in underground cables: Rubber, varnished cambric and impregnated paper, cables carrying energy up to 15,000 volts are insulated with rubber. If the cable is exposed to the effects of chemicals or oils, it is usually coated with a synthetic material such as neoprene over a rubber insulator. For use in very hot areas, the cables are protected with asbestos or non-combustible plastics. If there is a possibility that the cable is corroded or water seeping into it, a lead shield is placed on the cable.
When insulated with polished calico, more layers are made than rubber or paper and the cable becomes rigid. Therefore, it is mainly used to insulate short connection cables in switchboards and similar auxiliary units. Polished calico is effective for cables of all sizes used at voltages up to 15,000 volts.
Insulation with wax paper is preferred because it reduces electrical energy loss and is low in cost. Such insulated cables are used up to 300,000 volts. But when exceeding 69,000 volts, the pressure of the duct where the cable is located is increased with oil or nitrogen gas. The purpose of the pressure is to eliminate the gaps or the places where the paper is separated from each other and to prevent the ionization of the gas in the gaps. It is impossible to prevent gaps while insulating the cable, both during the winding of the insulator to the cable and during the laying of the cable. The bends in the cable cause the insulating material layers to separate. Pressure up to 3.5 kg/cm² is required to prevent ionization at high voltage. Insulated with polished calico and oiled paper, the cables are usually covered with a protective lead layer. At the same time, certain precautions are taken against humidity. Because of the possibility of electrolysis or corrosion (rusting) in connection with the chemical structure of the soil, lead is covered with plastic. Synthetic materials are also used as insulators.
aerial cables
Lead-coated cables can be carried in the air in polar regions where conditions do not allow them to be installed underground.
The cable is carried on steel hangers supported by a strong steel cable called a guide cable. This type of aerial cable is generally used for distribution of electrical energy in residential areas where underground laying is not economical. It is also used in large factories because it is easier to maintain and more economical. Insulation of aerial cables is the same as for cables used underground. Precautions should be taken against humidity, corrosive atmosphere and abrasion caused by tree branches, for example.
low voltage cables
Generally, 3 types of cables are used in places not exceeding 1000 volts. These are cables covered with materials other than metal, metal-clad cables and mineral-insulated, metallic-sheathed cables. The cable, which is covered with a material other than metal, consists of conductors, each of which is insulated with rubber. Paper tape is wrapped around the rubber insulator covered with a layer of wax paper. Conductors thus insulated are wound with an outer winding impregnated with a moisture and fire resistant compound. A famous model of such cables is known as Romex.
Steel coiled cables
It consists of rubber insulated conductors, each of which is wrapped with wax paper, the conductors can be bent. Both types of cables, with and without steel braiding, are suitable for use in very arid areas where they are not buried in walls or concrete.
The steel braided cable is particularly resistant to wear.
