Wire and cable.
A power cable shall have the following technical characteristics
1, can withstand high working voltage and high long-term, has very excellent electrical insulation properties, so the power cable by using the voltage level can be divided into: low voltage (1 thousand volts and below), medium (6 - 35 thousand V), high pressure (66 - 330 thousand V) and ultra high voltage (500 thousand kV and above).
2, able to transmit a large current (hundreds of thousands or even thousands of security), so the use of cross-sectional area of several hundred or even thousands of square millimeters of conductive wire core. At the same time, the insulation and other materials are required to have good heat aging resistance, and the whole structure can keep the heat balance.
3, in order to make the cable can adapt to a variety of laying methods and the use of the environment (underground, water, ditch, tunnel, shaft), the use of a variety of combinations of protective layer structure.
In fact, the high voltage insulation technology, the high current transmission technology and the structural balance, the protective layer structure and so on, all represent the academic level of the electrical engineering.
(two) both wires and cables are used in power systems, so they are no longer classified as small classes, but classified by different insulating materials or structures.
(three) process equipment manufacturing power cable main insulation wire machine, coating equipment, cabling machine (3 - 5 insulation wire stranding), inner and outer sheath extrusion machine and sheathed (steel, steel wire armored equipment). Among them, different insulation structure using different equipment, and high technical requirements.
Power cable products are:
1, PVC insulated power cable with PVC plastic cheap, good physical and mechanical properties. The extrusion process is simple, but the insulation performance in general. Therefore, a large number of low-voltage power cables used to manufacture 1 thousand volts and below for low-voltage distribution system, with an annual output of up to about one hundred thousand km. Such as the use of a voltage stabilizer insulation material, allowing the production of 6 thousand volts class cable.
2, XLPE insulated power cable, because polyethylene is the best electrical insulation properties of plastics, coupled with high molecular weight after cross-linking into thermosetting materials, so its electrical properties, mechanical properties and good heat resistance. In the past twenty years, it has become the leading variety of medium and high voltage power cable in our country. It can be applied to the voltage level of 6 - 330 thousand volts.
In recent years, the cross-linking 1 thousand volt low voltage cable has become a trend of technology, the key is to reduce the thickness of insulation and PVC cable competition in price.
3, viscous oil impregnated insulation power cable in 1992 is the leading product of China's medium voltage cable. This is the classic structure of the power cable, has more than 100 years of history, electrical and thermal performance margin, long service life (1923 laying cable for domestic imports still). However, due to the production process, long cycle, less materials, etc., has been replaced by XLPE cable.
4, oil filled cable is another structure with thin oil paper cable, insulating paper wrapping, low viscosity oil under pressure to fill the gap in. Suitable for 66 - 500 thousand volts. Since 60s of last century, it is the only product of high voltage cable in our country, but in recent years, it has been replaced by XLPE insulated high voltage cable.
5, rubber insulated power cable is a kind of soft, can be used to move the power cable, mainly used for enterprises often need to change the location of the laying of the occasion. The use of natural rubber insulation, voltage rating is mainly one thousand volts, can produce a class of 6 thousand volts.
6, overhead insulated cable is essentially a insulated overhead conductor, because still erected on the pole, the insulation design margin can be smaller than the power cable. Insulation can be used polyvinyl chloride or crosslinked polyethylene. Generally made of single core, but also can be 3 - 4 phase insulation core twisted into a bundle, without sheath, known as the cluster type aerial cable
