Purpose of the paper is to show how the combination of PRPD-shape analysis and pulse-signal separation allow a significant improvement with respect on pass/fail criteria based only on PD amplitude threshold levels provided in pC with calibration or in mV without calibration.
It will shown that two specific types of PRPD patterns can be associated to distributed micro-void PD: one detected during the voltage conditioning, the other in almost steady state conditions. These patterns can be clearly identified even in the presence of additional noise or insulation defects (after signal separation) as well as using different PD measurement systems (instruments and couplers) provided of an adequate sensitivity and testing machines having different sizes and ratings.
Significant examples of application of the proposed method to test machines in good conditions and provided with some insulation defects, will be reported and discussed in the paper to show its effectiveness.
