What is an electrical insulator?

Insulators are devices installed between conductors of different potentials or between conductors and grounded components and can withstand voltage and mechanical stress. There are many types of insulators in different shapes. Although the structures and shapes of different types of insulators are quite different, they are all composed of insulating parts and connecting fittings.

The insulator is a special insulation control that plays an important role in overhead transmission lines. In the early years, insulators mainly were used on telephone poles. Later, many disc-shaped insulators were hung on one end of high-voltage wire connection towers to increase the creepage distance. They were usually made of glass or ceramics and were called insulators.

Insulators should not fail due to various electromechanical stresses caused by changes in environmental and electrical load conditions, otherwise, the insulator will not play a significant role and will damage the use and operating life of the whole line.

Insulators can be divided into suspension insulators and tension insulators according to different installation methods, according to the different insulating materials used, they can be divided into porcelain insulators, glass insulators, and composite insulators (also called polymer insulators), according to different voltage levels used, they can be divided into low-voltage insulators and high-voltage insulators; according to the other environmental conditions of use, pollution-resistant insulators for use in polluted areas are derived; according to different types of voltage used, DC insulators are derived; there are also various special-purpose insulators, such as insulating cross arms, Semiconductor glazed insulators and tension insulators for power distribution, bobbin insulators, and wiring insulators, etc.

In addition, according to the different breakdown possibilities of insulating parts, they can be divided into two types: type A, which is a non-breakdown insulator, and type B, which is a breakdown-type insulator.

Suspension insulator

It is widely used in the insulation and mechanical fixation of high-voltage overhead transmission lines and busbars in power generation and substations. Suspension insulators can be divided into suspension insulator discs and long rod suspension insulators. Disc suspension insulator is the most widely used insulator for transmission lines. Long rod suspension insulators have been widely used in Germany and other countries.

Post insulator

Mainly used for insulation and mechanical fixation of busbars and electrical equipment in power plants and substations. In addition, post insulators are often used as electrical equipment components such as isolating switches and circuit breakers. Among post insulators, they can be divided into pin post insulators and long rod post insulators. Pin-type post insulators are mostly used in low-voltage distribution lines and communication lines, while long rod post insulators are mostly used in high-voltage substations.

Porcelain insulator

Insulators with insulating parts made of electrical ceramics. Electrical ceramics are baked from quartz, feldspar and clay. The surface of porcelain parts of porcelain insulators is usually covered with enamel to improve its mechanical strength, waterproof infiltration and increase surface smoothness. Among various types of insulators, porcelain insulators are the most commonly used.

Glass insulator

Insulators made of toughened glass. Its surface is in a state of compressive prestress. If cracks and electrical breakdown occur, the glass insulator will break into small pieces on its own, which is commonly known as "self-explosion". This feature eliminates the need for "zero value" detection of glass insulators during operation.

Composite insulator

Also called a synthetic insulator. The insulator is composed of a fiberglass resin core rod (or core tube) and an organic material sheath and shed. It is characterized by small size, lightweight, high tensile strength, and excellent anti-pollution flashover performance, but its anti-aging ability is not as good as that of porcelain and glass insulators.

Composite insulators include rod-shaped suspension insulators, insulating cross arms, pillar insulators, and hollow insulators (i.e. composite bushings). Composite bushings can replace porcelain bushings used in a variety of power equipment, such as transformers, lightning arresters, circuit breakers, capacitive bushings, and cable terminals. Compared with porcelain sleeves, in addition to having the advantages of high mechanical strength, lightweight, and small dimensional tolerance, it can also avoid damage caused by explosion.