Voltage shape of impulse breakdown in internal insulation of VI

Experimental studies of impulse dielectric strength of the samples, differed by the most probable area of initiation and path of breakdown have been carried out. Two types of samples have been considered: 1) providing the breakdown of the contact gap and 2) providing combined breakdown, including flashover along the insulator. It has been established that if the discharge current is limited by the resistor the breakdowns of such samples have substantially different typical shapes and durations of the voltage drop. The authors suggest that analysis of voltage drop can help in determining the area of breakdown.