Insulator is used to support and fix busbar with electric conductor, and provide sufficient distance and insulation between each electric conductors or conductor and ground. Insulator is usually made of glass or ceramic as a kind of special insulation control, and plays an important role in the overhead transmission line.

1. Insulator is usually divided into breakdown type and non-breakdown type.

2. According to the structure, Insulator is divided into column (pillar) insulators, suspension insulator, needle insulator, butterfly insulator, strain insulator, pollution proof insulator and bushing insulator.

3. According to the application, Insulator is divided into line insulator, power plant insulator, and electrical insulator. Breakdown type insulator for line application has needle type, butterfly type and bar suspension type; non-breakdown type insulator has cross arm type and rod suspension type. The breakdown type insulator for power plant, electrical system application has needle type column, hollow column and bushing type; non-breakdown type has rod shaped column and porcelain container.

4. The insulators used in overhead line normally have needle type, butterfly type, suspension type, porcelain pole arm type, bar type and strain type etc.