Porcelain post insulators are an important part of electrical equipment in power grids and power plants. The main factors affecting the mechanical strength of pillar porcelain insulators are production process, material stress and operating environment. Defects such as interlayers, pores, and microcracks are mostly caused by the manufacturer's poor firing level, and most of them are concentrated in the same batch of products from the same manufacturer. Statistics show that about 95% of the defects occur near the flange, which is caused by the concentration of internal stress caused by the different expansion coefficients of materials. The impact stress and unidirectional shear stress caused by the long-term operation of the disconnector and the porcelain post at the tube mother are the high-incidence areas for the fracture of the porcelain post insulator.
Post insulators are mainly used for insulation and mechanical fixing of bus bars and electrical equipment in power plants and substations. Additionally, post insulators are commonly used as components of electrical equipment such as disconnectors and circuit breakers. In post insulators, it can be divided into pin type post insulators and rod type post insulators. Pin-type post insulators are mostly used in low-voltage distribution lines and communication lines, and rod-type post insulators are mostly used in high-voltage substations.
Post insulator manufacturers consider porcelain insulators to be insulators made of electronic ceramics. Electronic ceramics are fired from seasoning, feldspar and clay. The surface of porcelain insulators is usually covered with enamel to improve its mechanical strength, prevent moisture penetration, and increase surface finish. Among various insulators, porcelain insulators are widely used.
The insulator of the glass insulator is made of tempered glass. Its surface is in a state of compressive prestress. If there is a crack and electrical breakdown, the glass insulator will automatically break into small pieces, commonly known as "self-explosion". This feature eliminates the need for "zero value" detection during operation of glass insulators.
Post insulator manufacturers believe that composite insulators are also called composite insulators. The insulator consists of a glass fiber resin core rod (or core tube), an organic material sheath and an umbrella shed. It is characterized by small size, light weight, high tensile strength and excellent pollution flashover resistance. But the anti-aging performance is not as good as porcelain insulators and glass insulators. Composite insulators include: rod-shaped suspension insulators, insulating cross-arms, post insulators and hollow insulators (ie composite bushings). Composite bushings can replace porcelain bushings used in a variety of electrical equipment, such as transformers, arresters, circuit breakers, capacitor 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 blasting.
Post insulator manufacturers believe that pollution-resistant insulators mainly take measures to increase or expand the shed or edge of the insulator to increase the creepage distance of the insulator and improve the electric strength of the insulator in a polluted state. At the same time, the structural shape of the shed is changed to reduce the amount of natural pollution on the surface, thereby improving the anti-pollution flashover performance of the insulator. The creepage ratio of pollution-resistant insulators is generally 20%~30% higher than ordinary insulators, or even more. Double-layer umbrella-shaped pollution-resistant insulators are used in China's power grid pollution flashover-prone areas. This insulator has strong self-cleaning ability and is easy to clean manually.