What Is an Insulator?

A device capable of withstanding the effects of voltage and mechanical stress installed between conductors of different potentials or between a conductor and a grounded member. There are many types of insulators and different shapes. Although the structure and shape of different types of insulators are quite different, they are composed of two major parts, namely insulators and connecting hardware.

According to different installation methods, insulators can be divided into suspension insulators and pillar insulators; according to the insulation materials used, they can be divided into porcelain insulators, glass insulators and composite insulators (also known as composite insulators); according to different voltage levels, they can be divided into It is a low-voltage insulator and a high-voltage insulator; according to the different environmental conditions, the pollution-resistant insulators used in polluted areas are derived; the DC insulators are derived according to the types of voltages used; there are also various special-purpose insulators, such as insulation crossarms, Semiconductor glaze insulators and tensioning insulators for power distribution, bobbin insulators and wiring insulators. In addition, according to the possibility of breakdown of insulators, it can be divided into two types: A-type non-breakable insulators and B-type breakdown insulators.

Suspension insulators are widely used in the insulation and mechanical fixing of high-voltage overhead transmission lines and soft buses in power generation and substations. In the suspension insulator, it can be divided into a disc-shaped suspension insulator and a rod-shaped suspension insulator. Disk suspension insulator is the most widely used insulator for transmission lines. Rod-shaped suspension insulators have been widely used in Germany and other countries.

Pillar insulators are mainly used for insulation and mechanical fixing of bus bars and electrical equipment in power plants and substations. In addition, pillar insulators are often used as part of electrical equipment such as disconnectors and circuit breakers. In pillar insulators, they can be divided into pin-type pillar insulators and rod-shaped pillar insulators. Pin-type pillar insulators are mostly used for low-voltage power distribution lines and communication lines, and rod-shaped pillar insulators are mostly used for high-voltage substations.

Porcelain insulator insulator is an insulator made of electrical ceramics. Electric 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 most commonly used.

Glass insulator insulator is an insulator made of tempered glass. Its surface is in a state of compressive prestressing. If cracks and electrical breakdown occur, the glass insulator will rupture itself into small fragments, commonly known as "self-explosion." This feature eliminates the need for "zero" testing of glass insulators during operation.

Composite insulators are also called synthetic insulators. The insulator consists of a glass fiber resin core rod (or core tube), an insulator composed of an organic material sheath and an umbrella skirt. Its characteristics are small size, light weight, high tensile strength and excellent anti-pollution flashover performance. But the anti-aging ability is not as good as porcelain and glass insulators. Composite insulators include: rod-shaped suspension insulators, insulation crossarms, post insulators, and hollow insulators (that is, composite bushings). Composite bushings can replace a variety of porcelain sleeves used in power equipment, such as transformers, arresters, circuit breakers, capacitor bushings, and cable terminations. Compared with porcelain sleeves, in addition to its advantages of high mechanical strength, light weight and small dimensional tolerances, it can also avoid damage caused by blasting.

Low-voltage insulators and high-voltage insulators Low-voltage insulators refer to insulators used in low-voltage power 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 insulator pillars.

Pollution-resistant insulators are mainly taken to increase or increase the insulator umbrella skirt or edge of the insulator to increase the creepage distance of the insulator to improve the electrical strength of the insulator in a dirty state. At the same time, the shape of the umbrella skirt structure was changed to reduce the amount of natural dirt on the surface to improve the anti-pollution flashover performance of the insulator. The creepage distance of pollution-resistant insulators is generally 20% to 30% higher than that of ordinary insulators, or even more. China's grids with frequent pollution flashovers are accustomed to the use of double-layer umbrella-shaped pollution-resistant insulators, which have strong self-cleaning capabilities and are easy to clean manually.

DC insulators are mainly disc insulators used in DC transmission. DC insulators generally have a longer creepage distance than AC pollution-resistant insulators, and their insulators have a higher volume resistivity (not less than 10 · m at 50 ° C), and their connection hardware should be equipped with the sacrifice of electrolytic corrosion protection. Electrode (such as zinc sleeve, zinc ring).

Type A insulator and type B insulator Type A is a non-piercing type insulator. Its dry flashover distance is less than 3 times (drying resin) or 2 times (other materials) the dry breakdown distance: Type B can be broken down. Type insulator, its breakdown distance is less than 1/3 (pouring resin) or 1/2 (other materials) of dry flashover distance. Insulator dry flashover distance refers to the shortest distance through the air along the outer surface of the insulator; breakdown distance refers to the shortest distance through the insulating material of the insulator. ^[2]

The main function of the insulator is to achieve electrical insulation and mechanical fixing. To this end, various electrical and mechanical performance requirements are specified. For example, under specified operating voltage, lightning overvoltage, and internal overvoltage, no breakdown or flashover occurs along the surface; under specified long-term and short-term mechanical load, no damage or damage occurs; After long-term operation under electrical load and various environmental conditions, no obvious degradation will occur; the metal fittings of the insulator will not produce obvious corona discharge at the operating voltage, so as not to interfere with radio or television reception. Because insulators are used in a large number of devices, the connection hardware is also required to be interchangeable. In addition, the technical standards of insulators also require various electrical, mechanical, physical, and environmental condition tests on insulators to verify their performance and quality according to different models and use conditions.

In humid weather, dirty insulators are prone to flashover discharge, so they must be cleaned to restore the original insulation level. General area one year

There are more than 200 line insulator manufacturing companies in China, of which about 40 have a certain production scale. Tempered glass insulators have been used in more than 100 countries in the world, with more than 200 million pieces. Due to the accelerated construction of the power grid, compared to porcelain insulators, the development of domestic glass insulators is more rapid, and its market supply exceeds demand, and has continuously attracted other companies to compete in this field.
Since 2004, the main business income of major enterprises in China's insulator arrester industry has continued to grow rapidly, with an average annual growth rate close to 25%. With the improvement of the technical level of China's insulating product manufacturing industry and the acceleration of the economic development of East and South Asia, major domestic enterprises seize the opportunity to actively explore the international market, and the export delivery value of the industry has increased year by year. According to relevant research forecasts, the compound annual growth rate of sales of insulator arrester manufacturing industry in China from 2012 to 2015 is 17.83%. In 2015, the sales revenue of domestic insulator arrester industry will reach 40.3 billion yuan.
In recent years, China's power industry has developed rapidly, and the installed capacity of generators has increased year by year. According to statistics, China s installed power generation capacity in 2010 was 962 million kilowatts, a year-on-year increase of 10.08%. As an indispensable component of power transmission and transformation equipment, insulator lightning arresters are inseparable from the development of the power industry.

The power industry is the most important application market for insulator arrester products. Many current power projects in China, such as the construction and transformation of urban and rural power grids, the transmission of electricity from the west to the east, the construction of electrified railways, and the launch of the UHV product market are not only for the insulator arrester industry The development of the company provides a broad market space, but also puts forward new requirements for the industry product market, and promotes the adjustment of the market structure of insulator arrester products and the research and development of new technologies.