What covered conductor?
Covered conductors consist of a conductor surrounded by a covering made of insulating material as protection against accidental contacts with other covered conductors and with grounded parts such as tree branches, etc
Three common covered conductors
Polyvinyl chloride (PVC) material is cheap, has good physical and mechanical properties, simple extrusion process, light specific gravity, good oil and corrosion resistance, but general insulation performance parameters, so it is used in large quantities to manufacture low-voltage wires and cables of 1kV and below. The use of insulating materials with added voltage stabilizers allows the production of 6K cables but is not suitable for use in 6w more important circuits. The cable is convenient to lay, and it is easy to make the terminal and the middle joint. The suitable climate temperature range of ordinary PVC is -1560℃, and the temperature cannot be lower than -5℃ during laying. When it is lower than 0℃, the wires and cables should be heated first in severe cold areas below 15℃. Cold-resistant PVC cables should be used. Insulation will accelerate aging under high temperature or sunlight. After adding a heat-resistant plasticizer, a core with a long-term allowable working temperature of 90°C and a heat-resistant polyvinyl chloride cable of 105°C can be manufactured. It is suitable for use in an environment with a temperature of 50°C or higher, but it requires wire joints or patterns. The joint is soldered.
Ordinary polyvinyl chloride has certain flame redundancy, but it will release toxic fumes when burned. It is not suitable for occasions where low smoke and low toxicity requirements need to be met when burning, such as underground passenger transportation facilities, underground business districts, high-rise buildings and special important Public facilities and other places with dense crowds or factories with high importance. European countries have stipulated the elimination of polyvinyl chloride cables in civil buildings. Polyvinyl chloride cables are not suitable for soils containing chemical agents such as benzene and anilines, ketone pyridine, methanol, ethanol, acetaldehyde, etc.; it is not suitable for use in soils containing trichloroethylene, chloroform, carbon tetrachloride, carbon disulfide, Acetic anhydride, ice vinegar.
XLPE has superior electrical insulation performance parameters and becomes a thermoset material with good mechanical properties and heat resistance after polymer cross-linking. In the past 20 years, it has become the leading variety of medium and high-voltage power cables in my country. It can be applied to various voltage levels from 6 to 330kV. The ⅪPE voltage level can be up to 500kV. At present, the current carrying capacity of 1kV XLPE cables of the same cross-section is about 1/4 higher than that of PVC cables, the price is about 1/3 higher, the insulation thickness is thinner, and the quality is lighter. The cost performance of the two is not much different. Low-voltage XLPE cables have developed rapidly since they were put into use in the mid-1990s, and currently have half of the market share with PVC cables. XLPE cable also has the characteristics of simple structure, convenient manufacturing, light specific gravity, convenient laying, corrosion resistance, and easy terminal and intermediate joints. It has better low temperature resistance than PVC cables, and the insulation layer has greater hardness and strength than PVC insulation, and it is difficult to peel off. XLPE cables are halogen-free, non-flammable, and will not produce a large amount of toxic gas and smoke when burned. If flame retardants are added, the mechanical and electrical performance will be reduced. The radiation process can be used to increase the temperature resistance to 125~135℃. And improve the mechanical and electrical properties. It is more sensitive to ultraviolet radiation, so PVC is usually used as the outer sheath material. Covering and shading measures should be taken when exposed to strong sunlight for a long time in the open environment. XLPE cables should adopt a waterproof structure that prevents dry cross-linking formed by water trees and three-layer co-extrusion of internal and external conductive and insulating layers, especially for important circuits of 6KV and above and when laying underwater.
The insulation voltage level of natural rubber is mainly 1kV, which can produce 6W level. It has good bending performance and can be laid in severe cold weather. It is especially suitable for mobile electrical equipment and other circuits that often need to be bent or have higher flexibility requirements, and where the horizontal height difference is large and vertical laying. When encountering oils and their compounds, they are quickly damaged. Oil-resistant rubber sheathed cables should be used in places that may be often soaked in oil.