Applicability of coefficients for the defect identification of partial discharges in air under AC voltage stress based on the pulse shape

Partial discharge diagnosis is an established instrument for the condition assessment of high voltage insulations and equipment. Under AC voltage stress the phase resolved pattern is of great significance in order to become aware of the type of fault. As a result of the inapplicability for DC voltage stress, approaches for alternative interpretation techniques such as the analysis of the pulse shape were identified in recent investigations. In this paper it is shown, that coefficients based on the pulse shape are also applicable for the defect identification of partial discharges under AC voltage stress. A method for analysing the pulse shapes of corona discharges, surface discharges and contact noise in air occurring in the negative and the positive half-wave of the test voltage is proposed and discussed.