The basic properties of pin insulators include electrical, mechanical and thermal properties. In addition, there are resistance to the environment and aging. Electrical properties of PIN insulators: Destructive discharge along the insulating surface is referred to as flashover, while flashover characteristics are the primary electrical characteristics of PIN insulators. For different voltage levels, the pin-type insulators have different withstand voltage requirements. This indicator is the influence of dry and wet power frequency withstand voltage, lightning impulse withstand, shock wave pressure, working pressure and so on.
In order to avoid operational failure, the breakdown voltage of the insulator is higher than the flashover voltage. In factory tests, porcelain insulators can be broken down, which is usually caused by a spark test, that is, high pressure causes the insulating surface to generate frequent sparks so that it can be held for a certain period of time to see if it is punctured.
Some insulators must be subjected to corona test, radio interference test, partial discharge test and dielectric loss test. In high-altitude insulators, the electrical strength is reduced due to the decrease in air density. Therefore, the withstand voltage conversion to standard atmospheric conditions should be improved accordingly. The flashover voltage of the dirty insulator is lower than the dry and wet flashover voltage. Therefore, the contaminated area should be reinforced or anti-fouling type insulator. The creepage distance (ratio of creepage distance to rated voltage) should be higher than that of ordinary type. .
Compared with AC insulators, DC pin insulators have poor electric field distribution, low adsorption of dirt and electrolysis, and low flashover voltage. They have special structural design and general requirements, and the creepage distance is larger.