Post insulator is a special insulation control, which can play an important role in overhead transmission lines. In the early years, post insulators were mostly used for electric poles, and gradually developed into high-voltage wire connection towers with a lot of suspended insulators hanging at one end. It is to increase the creepage distance, usually made of silica gel or ceramics, called insulators. Insulator plays two basic roles in overhead transmission line, namely supporting conductor and preventing current from returning to ground. These two roles are guaranteed. Insulator should not fail due to various mechanical and electrical stresses caused by changes in environment and electrical load conditions. Otherwise, insulator will not play a significant role and will damage the service life and operation life of the whole line.



1、 Scope of application, use conditions and classification:
The outdoor rod-shaped post porcelain insulator is suitable for the insulation and support of the conductive part in the power frequency AC system nominal voltage 35-750kv substation, power distribution device and power station electrical equipment. The altitude of the insulator installation site shall not exceed 1000m, and the ambient temperature shall be - 40 ℃ ~ + 40 ℃.
According to the cleanliness of the atmosphere, insulators are divided into three types: common type, pollution resistant type and heavy pollution resistant type.
According to the different supporting electrical equipment, it can be divided into three types: bus bar, disconnector pole, wave arrester pole and air reactor pole.

2、 Structural features:
The insulator is made of porcelain parts and upper and lower metal accessories with cement adhesive. Brown glaze is applied on the surface of porcelain parts, or according to the color required by users.
The surface of metal accessories is hot-dip galvanized, and the insulator of 330kV and above used to support the bus is equipped with a grading ring at the top.
Standard umbrella type insulator is adopted for common type insulator (see Figure 1). The pollution-resistant and heavy pollution-resistant insulators are umbrella shaped with large and small umbrella phases and edges under the umbrella, which are optimized by artificial pollution test (see Figure 2). Because the small umbrella is not easy to be polluted under the protection of the big umbrella, and the distance between the big umbrella is large, the discharge characteristics between the umbrella are improved, so the pollution resistance of the insulator is improved, and it is conducive to the charged water washing.
The heavy pollution resistant insulator is suitable for 0.08-0.25mg/cm2 salt tight condition.

3、 Technical standards:
The insulator shall be manufactured in strict accordance with iec168 test for internal and outdoor porcelain or glass post insulator of system users with nominal voltage higher than 1000V, gb8287.1 technical conditions for high voltage post insulator and gb12744 pollution resistant outdoor post insulator.

4、 Electrical performance: