1. Dry lightning voltage: the low voltage required to make the insulator flashover when its surface is dull.

2. Wet lightning voltage: the low voltage between the surface of the insulator when the rain falls at an Angle of 45° with the horizontal surface.

3, breakdown voltage: when insulation aging, insulation components are damaged and even burst, lose insulation function is called insulator breakdown. Breakdown voltage refers to the low voltage that the insulation element of an insulator is damaged by breakdown and loses its insulation effect.

4, insulation leakage interval: insulation leakage interval refers to the curve length of the surface of the insulating element, that is, the creepage interval of the insulation surface between the two electrodes, commonly known as "creeping distance"