Insulators for electrical equipment or conductors subjected to potential differences in electrical insulation and mechanical fixation with the device, it is used to support the conductor insulator. Insulators can ensure that the conductor and cross-arms, towers have sufficient insulation. It should be able to withstand the vertical direction of the conductor load and the horizontal direction of the tensile force in operation, but also withstand the sun, rain, climate change and chemical corrosion, therefore, the insulator should have good electrical properties, but also to have sufficient mechanical strength. We commonly used insulators according to the material points are porcelain insulators (we often called porcelain vase), glass insulators, synthetic insulators and so on.
Insulator string refers to two or more insulator elements combined, usually we say that the insulator string also contains insulators on both sides of the connecting fittings, insulators used to suspend the wire and make the wire with the tower and earth insulation. So the insulator string contains insulators, insulators are part of the insulator string.
The following is illustrated by a diagram: