绝缘子用以悬挂并对接地体保持电气绝缘。接触网上所用的绝缘子一般为瓷质的，即在瓷土中加入石英和长石烧制而成表面涂有一层光滑的釉质。较为理想的新型绝缘子是复合式聚合绝缘子。
Insulators are used for suspension and electrical insulation of grounding bodies. The insulators used on the contact wire are usually made of porcelain, i.e. the ceramic clay is fired with quartz and feldspar to form a smooth enamel coating on the surface. The ideal new insulator is composite polymer insulator.
这种绝缘子由两种聚合材料结合制成，一种材料提高机械强度，另一种材料提高绝缘性能，使复合式聚合绝缘子可以满足机械强度高、绝缘性能好、耐冲击、耐电弧重量较轻等的要求，这也是未来绝缘子发展的方向。
This kind of insulator is made of two kinds of polymer materials. One kind of material improves the mechanical strength, the other kind of material improves the insulation performance, so that the composite polymer insulator can meet the requirements of high mechanical strength, good insulation performance, impact resistance and lighter arc resistance. This is also the direction of the future development of insulators.