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Classification of insulation materials

2019-05-27

Silicone waterproof sealing rings include gas insulating materials, liquid insulating materials and solid insulating materials. Involved in electrical, petrochemical, light industry, building materials, textiles and many other industries.


Gas insulating material


Under normal circumstances, the dry gas at normal temperature and pressure has good insulation properties. As a gas dielectric material for an insulating material, it is also required to meet physical, chemical, and economic requirements. Air and sulfur hexafluoride gas are commonly used gas insulating materials.


The air has good insulation properties, and its insulation performance can be automatically restored instantaneously after breakdown. The electrical and physical properties are stable, the source is extremely rich, and the application surface is wide. However, the breakdown voltage of air is relatively low, the electrodes are sharp, the distance is short, the voltage waveform is steep, the temperature is high, the humidity is high, and other factors can reduce the breakdown voltage of the air. The compressed air or vacuum is often used to improve the air blow. Wear voltage.


Sulfur hexafluoride (SF6) gas is a kind of inert gas which is non-combustible, non-explosive, colorless and odorless. It has good insulation performance and arc-extinguishing ability, far higher than air, and has been widely used in high-voltage electrical appliances. Sulfur hexafluoride gas also has excellent thermal stability and chemical stability, but at a high temperature of 600 ° C or higher, sulfur hexafluoride gas will be decomposed and toxic substances will be produced. Therefore, the following aspects should be noted in use.


(1) Strictly control the water content and do dehumidification and moisture protection measures.


(2) Use appropriate adsorbents to absorb harmful substances and water.


(3) The pressure of sulphur hexafluoride gas in the circuit breaker should not be too high and liquefaction occurs.


(4) The place where the sulphur hexafluoride equipment is placed should have good ventilation conditions.


(5) It is necessary and reliable labor protection measures for the operation and maintenance personnel.


Liquid insulation


Insulating oils are natural mineral oils, natural vegetable oils and synthetic oils as shown. Natural mineral oil is widely used. It is obtained from petroleum crude oil through various degrees of refining and refining.


A neutral liquid in golden yellow with good chemical stability


Sexual and electrical stability. Mainly used in power transformers, oil-less circuit breakers, high-voltage cables, oil-immersed capacitors and other equipment. Natural vegetable oils include castor oil, soybean oil and the like. Synthetic oils include oxidized biphenyl methyl silicone oil, benzyl silicone oil, etc., and are mainly used in power transformers, high voltage cables, and oil-impregnated paper capacitors.


Insulating oil can be contaminated and aged due to various factors during storage, transportation and operation. Heat and oxygen play a major role in the aging of oil. The measures taken in the industry to prevent oil aging include: strengthening heat dissipation to reduce oil temperature; using nitrogen and film to isolate transformer oil from air; using desiccant to eliminate moisture; adding antioxidants; and preventing sunlight. After the oil is contaminated, it can be purified and regenerated by pressure filtration or electric purification.


In order to ensure the safe operation of oil-filled equipment, it is necessary to always check the oil temperature rise, oil level, oil flash point, acid value, breakdown strength and dielectric loss tangent, and if necessary, chromatographic analysis of transformer oil. When replenishing the oil, try to use the original model or similar model, and should carry out the mixing test.


Solid insulation


There are many types of solid insulating materials, and their insulating properties are excellent, and they are widely used in power systems. Commonly used solid insulating materials are: insulating varnish, insulating rubber; fiber products; rubber, plastic and its products; glass, ceramic products; mica, asbestos and its products.


Insulating varnish and insulating rubber are all important insulating materials based on high molecular polymer and can be cured into insulating hard film or insulating whole under certain conditions.


The insulating varnish is mainly composed of a lacquer base, a solvent, a diluent, a filler and the like. The insulating varnish has a high dielectric strength after being formed and cured, and can generally be used as an impregnating or coating insulating of a motor or an electrical coil. According to the use, it can be divided into impregnating varnish, enameled wire lacquer, covering lacquer, silicon steel lacquer and anti-corona lacquer.


Insulating glue is similar to insulating varnish. It is generally filled with filler. It is widely used for pouring cable joints, bushings, current transformers of 220kV and below, and voltage transformers of 10kV and below. The insulating glue used is yellow cable glue, black cable glue, epoxy cable glue, epoxy resin glue, epoxy polyester glue and the like.


Insulating fiber products are insulating materials made of insulating paper, cardboard, paper tubes, and various fiber fabrics. The impregnated fiber product is made of insulating fiber products as the substrate and immersed in insulating varnish. It has certain mechanical strength, electrical strength and moisture resistance, and also has some special functions such as mildew proof, electric proof and radiation protection. Insulating electrical laminates are made of fiber as a substrate, dip coated with different adhesives, and are hot-pressed or rolled into a layered structural insulation material whose properties depend on the substrate and the adhesive and its molding process. It can be made into products with excellent electrical properties, mechanical properties and heat, mildew, arc resistance, corona resistance and other characteristics.


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