A high voltage insulator is a specialized device used to isolate and support electrical conductors in high voltage systems. It is primarily made from porcelain, glass, or composite materials with excellent electrical insulation properties.

Its primary function is to prevent the flow of electric current between the conductor and the surrounding structure, thus ensuring safety and reliable operation of power transmission and distribution networks. 

The firing temperature for high voltage insulators varies depending on the type of material used and the specific requirements of the application. Porcelain high voltage insulators are typically fired at temperatures ranging from 2200°F to 2500°F (1200°C to 1370°C).