Valuable information! Classification and applications of insulators

Classification of Insulators
Insulators can be classified into high-voltage insulators and low-voltage insulators based on the operating voltage.
Insulators can be classified according to their manufacturing materials into porcelain insulators, glass insulators, and organic-material (epoxy-resin-cast) insulators.
Insulators can be classified into indoor insulators and outdoor insulators based on their installation location.
Insulators can be classified into 11 subcategories and 48 series based on their structure and intended use.
The primary uses of insulators
1) High-voltage line insulators
① High-voltage line rigid insulators: These include pin-type porcelain insulators, porcelain cross-arm insulators, and butterfly-type porcelain insulators, among others.
High-voltage line porcelain cross-arm insulators can be classified into four types according to their structural forms: all-porcelain type, cement-bonded type, single-arm type, and V-shaped type. According to their installation method, they can be divided into two types: upright type and horizontal type. Based on the 50% full-wave impulse flashover voltage, they are available in the following voltage ratings: 185 kV, 210 kV, 280 kV, 380 kV, 450 kV, and 610 kV. These insulators are used in high-voltage overhead transmission and distribution lines, where they can replace pin-type and suspension insulators and eliminate the need for tall porcelain cross-arms.
High-voltage line butterfly-type porcelain insulators are classified into two voltage ratings: 6 kV and 10 kV.
It is used on overhead transmission and distribution line terminals, tension poles, and angle poles as an insulating and fixing component for conductors. It is also widely employed in conjunction with suspension insulators to serve as a component of line hardware, thereby simplifying the hardware structure.
② High-voltage line suspension insulators: These include disc-type porcelain suspension insulators, disc-type glass suspension insulators, porcelain rod insulators, and ground wire insulators, among others.
Disc-type suspension porcelain insulators for high-voltage lines are available in two types: standard and pollution-resistant. They are used on high- and extra-high-voltage transmission lines to suspend or tension conductors and ensure electrical insulation from the tower poles. Suspension insulators feature high mechanical and electrical strength; by varying the number of units in a string, they can be adapted to different voltage levels and meet diverse strength requirements, making them the most widely used type. The standard type is suitable for general industrial areas. In comparison with the standard type, the pollution-resistant insulator boasts a longer creepage distance and a design that facilitates cleaning by rain and wind, making it ideal for use in coastal regions, areas affected by metallurgical dust, chemical pollutants, and other regions with severe industrial contamination. When used in these environments, pollution-resistant insulators allow for smaller tower dimensions, thereby offering significant economic benefits.
Disc suspension glass insulators for high-voltage lines serve essentially the same purpose as disc suspension porcelain insulators for high-voltage lines. Glass insulators feature high mechanical strength, excellent resistance to mechanical impacts, superior thermal and cold performance, long service life, and outstanding electrical performance as well as excellent lightning withstand capability. Moreover, when damaged during operation, the shed of a glass insulator automatically breaks, making it easy to detect and significantly reducing the workload associated with insulation testing.
High-voltage porcelain pull rod insulators are used on terminal tension and angle poles of overhead power lines rated 10 kV and below, serving both as insulation and for securing conductors. They can replace certain types of butterfly porcelain insulators and disc suspension porcelain insulators.
③ Rod-type porcelain insulators for electrified railway catenary systems
2) Low-voltage line insulators
① Low-voltage line pin-type, butterfly-type, and rod-type porcelain insulators: Low-voltage pin-type porcelain insulators are used in overhead power lines below 1 kV for insulation and wire fixing. Low-voltage butterfly-type porcelain insulators are employed at the terminals, tension poles, and angle poles of power distribution lines for insulation and wire fixing. Low-voltage rod-type porcelain insulators are also used at the terminals, tension poles, and angle poles of power distribution lines for insulation and wire fixing.
② Overhead line tension porcelain insulators: Used on overhead transmission and distribution lines, as well as communication lines, at terminal corners or on poles with large spans for both AC and DC systems. They balance the tensile forces acting on the poles and serve to provide tension insulation and electrical connection.
③ Insulators for tram lines: Used for insulating and tensioning conductors in tram lines, or as insulating and supporting components for conductive parts on trams and power stations.
④ Pin-type porcelain insulators for communication lines: Used for insulating and fixing conductors in overhead communication lines.
⑤ Insulating insulators for wiring: including drum-shaped insulators, porcelain cleats, and porcelain tubes, etc. They are used for low-voltage wiring.
3) High-voltage substation insulators
① High-voltage indoor post insulators for power stations: These insulators are used on busbars and switchgear in indoor power stations and substations with rated power-frequency voltages ranging from 6 to 35 kV. They serve as insulating supports for high-voltage conductive parts. Typically, they are installed at altitudes not exceeding 1,000 meters, under ambient temperatures ranging from -40°C to 40°C, and should be operated in environments free from pollution and condensation. Specially designed plateau-type insulators can be used in regions at altitudes of 3,000 meters and 5,000 meters.
② Outdoor pin-type post insulators: These are suitable for use as insulating components or on switchgear installations in electrical equipment with rated AC voltages ranging from 3 to 220 kV, in environments where the surrounding ambient temperature is between -40°C and +40°C and the altitude does not exceed 1,000 meters. They serve both to provide insulation and to securely hold conductors in place.
③ Outdoor rod-type post insulators: Used in high-voltage electrical equipment and high-voltage switchgear, they serve to provide insulation and secure conductors. They have largely replaced the use of outdoor pin-type post insulators.
④ Anti-pollution outdoor rod-type post insulators: Suitable for moderate pollution areas with salt deposit densities up to 0.1 mg/cm², serving as insulation and support for high-voltage electrical equipment and switchgear.
⑤ High-voltage bushings for wall penetration: including indoor wall-penetration bushings, outdoor wall-penetration bushings, busbar wall-penetration bushings, and oil-paper capacitive wall-penetration bushings, among others.
⑥ Electrical porcelain bushings: including transformer porcelain bushings, switchgear porcelain bushings, and current/voltage transformer porcelain bushings.
Transformer porcelain bushings include two major categories: bushing-type porcelain bushings for power transformers and testing transformers, as well as post-type porcelain bushings.
Switch porcelain bushings include porcelain bushings for bulk oil circuit breakers, porcelain bushings for minimum oil circuit breakers, porcelain bushings for load switches, explosion-proof switch porcelain bushings, porcelain bushings for isolating switches, and porcelain bushings for air circuit breakers, among others. They are primarily used as insulators for high-voltage leads of switches to ground, as well as containers for the insulation and internal insulation of circuit breakers.
The porcelain bushing of a current transformer and voltage transformer serves as an insulating component.