Composite cap and pin insulator can be divided into common insulator and anti-pollution insulator or anti-fog insulator. Anti-pollution composite cap and pin insulators design is suitable for high pollution areas.

Composite cap and pin insulator design principle:
Dirt, pollution, salt, and particularly water on the surface of a high voltage Composite cap and pin insulator can create a conductive path across it, causing leakage currents and flashovers. The flashover voltage can be reduced by more than 50% when the Composite pin insulator is wet. High voltage insulators for outdoor use are shaped to maximise the length of the leakage path along the surface from one end to the other, called the creepage length, to minimise these leakage currents. To accomplish the surface is moulded into a series of corrugations or concentric disc shapes. These usually include one or more sheds; downward facing cup-shaped surfaces that act as umbrellas to ensure that the part of the surface leakage path under the 'cup' stays dry in wet weather. Minimum creepage distances are 20–25 mm/kV, but must be increased in high pollution or airborne sea-salt areas.

Composite cap and pin insulator design is a source of application, the environment, the connection mode, the use of voltage grade, etc.