Insulators are categorized by installation methods into suspension insulators and支柱insulators; by the type of insulating material used, they are divided into porcelain insulators, glass insulators, and composite insulators (also known as synthetic insulators); by voltage grade, into low-voltage and high-voltage insulators; by environmental conditions, into anti-fouling insulators for polluted areas; by voltage type, into DC insulators; and there are also special-purpose insulators, such as insulating crossarms, semiconductor glazed insulators, tension insulators for distribution use, spool insulators, and wiring insulators, etc. Additionally, they can be further classified into A-type insulators that are non-penetrable and B-type insulators that are penetrable, based on the possibility of insulation breakdown.