Behavior of sloping side of partial discharge parallelogram and application

The authors present the results of an investigation of the parallelogram method used for partial discharge measurement in insulation systems. Emphasis is placed on the behavior of the slope of the sloping side of the parallelogram. Theoretical analysis is based on the assumption of an idealized model in which partial discharges occur. It is found that the slope of the sloping side of the parallelogram varies with test voltage for a given sample and two parallelograms with two slopes will be shown under two different test voltages. A twice-measuring method for the parallelogram is then developed, and the geometrical capacitance increment introduced when the void short-circuited completely in the insulation system is measured using this method. Attention is also given to the application of this method to measure the value of the capacitance increase due to short-circuiting the void completely on artificial samples