According to different installation methods, insulators can be divided into suspension insulators and post insulators; according to the different insulating materials used, they can be divided into porcelain insulators, glass insulators and composite insulators (also called composite insulators); according to different voltage levels, they can be divided into They are low-voltage insulators and high-voltage insulators; according to the different environmental conditions used, pollution-resistant insulators used in polluted areas are derived; according to the types of voltage used, DC insulators are derived; there are also various insulators for special purposes, such as insulating cross-arm, Semiconducting glaze insulators and tension insulators for power distribution, bobbin insulators and wiring insulators, etc. In addition, according to the different breakdown possibilities of insulators, it can be divided into two types: type A, that is, non-breakdown insulators, and type B, that is, breakdown insulators.
Suspension insulators are widely used in the insulation and mechanical fixing of high-voltage overhead transmission lines and soft busbars of power generation and substations. Among the suspension insulators, they can be divided into disc suspension insulators and rod suspension insulators. Disc suspension insulators are the most widely used insulators for transmission lines. Rod suspension insulators have been widely used in Germany and other countries.
Post insulators are mainly used for insulation and mechanical fixing of bus bars and electrical equipment in power plants and substations. In addition, post insulators are often used as an integral part of electrical equipment such as disconnectors and circuit breakers. Among post insulators, they can be divided into pin post insulators and rod post insulators. Pin-type post insulators are mostly used in low-voltage distribution lines and communication lines, and rod-shaped post insulators are mostly used in high-voltage substations.
Porcelain insulators are insulators made of electrical ceramics. Electrical ceramics are baked from quartz, feldspar and clay as raw materials. The surface of porcelain insulators is usually covered with enamel to improve its mechanical strength, waterproof infiltration, and increase surface smoothness. Among all kinds of insulators, porcelain insulators are the most commonly used.
Glass insulators are insulators made of tempered glass. Its surface is in a state of compression and prestress. If cracks and electrical breakdown occur, the glass insulator will break into small pieces by itself, commonly known as "self-explosion". This feature eliminates the need for "zero value" testing of glass insulators during operation.
Composite insulators are also called composite insulators. Its insulating part is an insulator composed of a glass fiber resin core rod (or core tube) and an organic material sheath and shed. It is characterized by small size, light weight, high tensile strength, and excellent anti-fouling flashover performance. But the anti-aging ability is not as good as porcelain and glass insulators. Composite insulators include: rod-shaped suspension insulators, insulating cross-arms, post insulators and hollow insulators (ie composite bushings). Composite bushings can replace porcelain bushings used in various electrical equipment, such as transformers, lightning arresters, circuit breakers, capacitive bushings and cable terminals, etc. Compared with porcelain sleeves, it not only has the advantages of high mechanical strength, light weight, and small dimensional tolerance, but also avoids damage caused by bursting.
Low-voltage insulators and high-voltage insulators Low-voltage insulators refer to insulators used for low-voltage distribution lines and communication lines. High-voltage insulators refer to insulators used in high-voltage and ultra-high-voltage overhead transmission lines and substations. In order to meet the needs of different voltage levels, different numbers of single (piece) insulators of the same type are usually used to form insulator strings or multi-section insulating posts.
Pollution-resistant insulators mainly take measures to increase or enlarge the shed or rib of the insulator to increase the creepage distance of the insulator, so as to improve the electric strength of the insulator under the polluted state. At the same time, the structural shape of the shed is changed to reduce the amount of natural pollution on the surface, so as to improve the anti-pollution flashover performance of the insulator. The creepage ratio of pollution-resistant insulators is generally 20% to 30% higher than ordinary insulators, or even more. The pollution-resistant insulators with double-layer umbrella structure are used in areas where pollution flashover frequently occurs in China's power grid. This kind of insulator has strong self-cleaning ability and is easy to clean manually.
DC insulators mainly refer to disc insulators used in DC transmission. DC insulators generally have a longer creepage distance than AC pollution-resistant insulators, and their insulators have higher volume resistivity (not less than 10Ω·m at 50°C), and their connecting fittings should be equipped with anti-electrolytic corrosion sacrifices. Electrodes (such as zinc sleeves, zinc rings).
Type A insulator and Type B insulator Type A is a non-breakdown type insulator, and its dry flashover distance is not as large as 3 times (casting resin) or 2 times (other materials) of the dry breakdown distance: Type B can break down Type insulators whose breakdown distance is less than 1/3 (casting resin) or 1/2 (other materials) of the dry flashover distance. The dry flashover distance of an insulator refers to the shortest distance through the air along the outer surface of the insulator; the breakdown distance refers to the shortest distance through the insulating material of the insulator.