Processing techniques applied to partial discharge measuring in rotating machines

During the last two decades, the measurement of partial discharges (PD) in rotating electrical machines that operate with high voltages is being the most effective method for detecting defects in their insulation. However, several inconveniences must be overcome by the technical analysts when on-line measurements are carried out. Among them, the most import is the high levels of background noise and interferences which, in many cases, affect significantly in the sensitivity of PD activity detection. In this article, three noise filtering techniques applied in PD measurements performed in a real installation are analyzed. In addition, the benefits of using advanced processing and diagnostic techniques for the evaluation of the dielectrics condition are evidenced. The practical experience presented was carried out in a HV installation comprising the alternator of a hydraulic plant, the plant substation and the insulated cable system that interconnects both parts. The results obtained highlight the importance of applying appropriate signal processing techniques when performing in-situ and on-line PD measurements in rotating machines.