The insulator is commonly called as porcelain vase, and it is the insulation part which is used to support the conductors. Insulators can ensure adequate insulation for wires, cross arms, and pole towers. It should be able to withstand the vertical load and horizontal tension of the conductor during operation. It also withstands corrosion from the sun, rain, climate change and chemicals. Therefore, insulators must have both good electrical properties and sufficient mechanical strength. The quality of insulators is very important to the safe operation of lines.
Insulators used in overhead lines commonly include porcelain insulator, pin type insulators, spool insulators, suspension insulators, cross arms insulators, rod insulators and tension insulators.
1. According to different installation methods, they can be divided into suspension insulators and post insulators.
Suspension Insulator:
It is widely used in the insulation and mechanical fixing of high voltage overhead transmission lines and soft busbars of electric station and substation. Suspension insulators can be divided into disc suspension insulator and rod suspension insulator. Disc suspension insulator is the most widely used insulator for transmission lines
Post Insulator:
Mainly used for insulation and mechanical fixation of busbars and electrical equipment in distribution lines, power plants and substations. In addition, post insulators are often used as components of electrical equipment such as isolating switches and circuit breakers. Post insulators can be divided into pin type post insulators and rod type post insulators. Pin post insulators are mostly used in low-voltage distribution lines and communication lines, while rod post insulators are mostly used in high-voltage substations.
2. In accordance with the insulator material, there are porcelain insulators, glass insulators, composite insulators and porcelain composite insulators.
Porcelain insulator:
The insulator is an insulator 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:
An Insulators made of tempered 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 polymer insulator (Synthetic Insulator).The insulation part is an insulator composed of a fiberglass resin core rod (or core tube) and a sheath and shed made of organic materials.
It is characterized by small size, light weight, 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 type suspension insulators, Cross Arm Insulator, post insulators and hollow core insulators (ie 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, it not only has the advantages of high mechanical strength, light weight and small dimensional tolerance, but also can avoid damage caused by explosion.
Porcelain composite insulator
An insulator that uses porcelain or glass as the inner insulator, high-temperature vulcanized silicone rubber umbrella material as the outer insulator, and all the porcelain or glass parts are covered.
3. According to the different voltage levels used, they can be divided into low-voltage insulators and high-voltage insulators.
Low-voltage insulators:
refers to insulators used for low-voltage distribution lines and communication lines.
High voltage insulator:
Refers 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 (pieces) of the same type are usually used to form insulator strings or multi-section insulating pillars.
4. According to the different environmental conditions of use, they are divided into ordinary insulators and anti-pollution insulator used in polluted areas.
Anti-pollution insulator:
The main measures are to increase or enlarge the insulator shed or ribs to increase the creepage distance of the insulator and improve the electrical strength of the insulator in a dirty state. At the same time, the structural shape of the shed is also changed to reduce the amount of natural dirt accumulation on the surface to improve the anti-pollution flashover performance of the insulator. The specific creepage distance of pollution-resistant insulators is generally 20% to 30% higher than that of ordinary insulators, or even more. Areas with frequent pollution flashovers in China's power grid are accustomed to using pollution-resistant insulators with a double-layer umbrella structure. Such insulators have strong self-cleaning capabilities and are easy to clean manually.
5. According to the different voltage levels used, they can be divided into low-voltage insulators and high-voltage insulators.
Low-voltage insulators:
refers to insulators used for low-voltage distribution lines and communication lines.
High voltage insulator:
Refers 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 (pieces) of the same type are usually used to form insulator strings or multi-section insulating pillars.
6. According to the different environmental conditions of use, they are divided into ordinary insulators and anti-pollution insulator used in polluted areas.
Anti-pollution insulator:
The main measures are to increase or enlarge the insulator shed or ribs to increase the creepage distance of the insulator and improve the electrical strength of the insulator in a dirty state. At the same time, the structural shape of the shed is also changed to reduce the amount of natural dirt accumulation on the surface to improve the anti-pollution flashover performance of the insulator. The specific creepage distance of pollution-resistant insulators is generally 20% to 30% higher than that of ordinary insulators, or even more. Areas with frequent pollution flashovers in China's power grid are accustomed to using pollution-resistant insulators with a double-layer umbrella structure. Such insulators have strong self-cleaning capabilities and are easy to clean manually.
| ANSI CLASS |
Disc dia. (mm) |
Unit spacing height (mm) |
Creepage distance (mm) |
Mechnical failing load (KN) |
Lower frequency flashover voltage |
Critical impulse flashover voltage |
Weight (kg) |
| Dry(kV) |
Wet(kV) |
Positive(kV) |
| 52-2 |
190 |
146 |
210 |
67 |
65 |
35 |
110 |
3.5 |
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