Partial discharge diagnostics for DC equipment

Partial discharges (PD) are an indication of weak spots in the insulation of DC high voltage equipment. For AC equipment, classification of the type of defect can be achieved if statistical tools are used on the PD phase distributions. In this paper, the authors propose the use of a similar technique for classification at DC voltage. One major adjustment has to be made: the phase angle used at AC voltage has to be replaced by the time between discharges at DC voltage. This method has been tried on artificial defects with success. Both the method and the test results are presented