Insulators mainly include the following types: suspension insulators, pillar insulators, porcelain insulators, glass insulators, composite insulators, low-voltage insulators and high-voltage insulators, pollution-resistant insulators, and DC insulators.
- Suspension insulators: Widely used in insulation and mechanical fixation 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 widely used in transmission lines. Rod suspension insulators have been widely used in Germany and other countries.
- Post insulators: 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: 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 most widely used.
- Glass insulator: an insulator 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 insulator: also known as composite insulator. Its insulating parts are insulators composed of glass fiber resin core rods, organic material sheaths and sheds. 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. 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 insulators of the same type are usually used to form insulator strings or multi-section insulating posts.
- Pollution-resistant insulators: measures are mainly taken to increase or increase the shed or edge 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, and their connecting fittings should be equipped with sacrificial electrodes to prevent electrolytic corrosion.