Composite line post insulators consist of a cylindrical insulating core, bearing the mechanical load, protected by a polymeric housing, the loads being transmitted to the core by metal fittings. Despite these common features, the materials used and the construction details employed by different manufacturers may be different.

Housing of composite line post insulator, external insulating part of a composite insulator providing the necessary creepage distance and protecting core from the environment.

Shed of composite line post insulator, insulator part, projecting from the insulaotor trunk, intended to increase the creepage distance. The shed can be with or without ribs.

End fitting of composite line post insulator, integral component or formed part of an insulator intended to connect it to a supporting

Composite line post insulators are used in both a.c. and d.c. applications. In spite of this fact a specific tracking and erosion test procedure for d.c applications as a design test has not yet been defined and accepted. Composite line post insulators are often used in braced structures whose geometry varies from line to line.