Impulse creeping discharge phenomena at insulator supporting points of aerial insulated wires

A thin groove was installed on the surface of insulated test wire longitudinally from the free end of the binding wire. Creeping discharge was photographed with the aid of an image intensifier. The effect of this groove on the progression of the leader stroke under dry and wet conditions was investigated. Positive creeping discharges are shown to progress with jumps across the surface of the wire. Negative ones progress while in contact with the surface. Under dry conditions, the progression distances of negative leader strokes in the presence of a groove are longer than those without a groove. Under wet conditions without a groove, progression distances of negative leader strokes are longer than those under dry conditions