What is a Disc Insulator? Definition: An insulator that is made up of high-grade wet processes like brown-green glazed is known as disc insulator. These insulators are used in transmission & distribution systems. The designs of these insulators mainly change based on customer requirements. The properties of every electrical insulator include the following. High resistivity Mechanical strength should be good for the conductor load. Dielectric strength is good For insulation material, its relative permittivity is high. It uses materials like non-porous or waterproof. The designing of these insulators can be done using different materials based on the application such as rubber, plastic, wood, mica, glass, etc. The exact insulating materials used in an electrical system are glass, porcelain, steatite, ceramic, polymer, PVC, etc. But, in electrical power systems, the insulators with porcelain material are the best and used in transmission & distribution system. Glass type materials are used in strain/ suspension type insulators.