Insulators are categorized by installation method into suspended 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-pollution insulators for polluted areas; by voltage type, into DC insulators. There are also various special-purpose insulators, such as insulating crossarms, semiconductor glaze insulators, tension insulators for distribution, reel insulators, and wiring insulators, etc. Additionally, based on the possibility of insulation breakdown, they can be classified into two types: A-type, non-breakdown insulators, and B-type, breakdownable insulators.