However, when encountering humid weather such as fog, dew, drizzle, melting ice, and snow, the dirt on the surface of the composite insulator absorbs water, causing the electrolyte in the dirt layer to dissolve and ionize, resulting in an increase in the conductance of the dirt layer. At this time, the composite insulator's Surface leakage current will increase.
Due to the influence of the shape and structural size of the composite insulator, as well as the uneven distribution of the dirt layer on the surface of the composite insulator and the different degrees of moisture, the current density at various parts of the surface of the composite insulator is different. As a result, dry spots are formed in the parts with relatively high current density. bring. For example, near the steel feet of suspension insulators and at the junction of rod-type pillar insulator skirts and core rods. The formation of the dry zone makes the surface voltage distribution of the composite insulator more uneven, and the dry zone bears higher voltage. When the electric field intensity is large enough, a glow discharge will occur. As the leakage current increases, the glow discharge may transform into a local arc. At this time, the surface of the composite insulator is equivalent to a local arc and a series of remaining dirt layer resistors. . The local arc at this time may be extinguished or may develop. Totally random. The thermal effect of the local arc will expand the dry area, and the local arc will rotate along the dry area and continuously adapt to its own length. When local arcs continue to occur and develop, reaching and exceeding the critical state, the arc penetrates both poles and completes flashover.
