The detection of partial discharges in on-line equipment

Well developed techniques are available for the detection of partial discharges (PD´s) in equipment tested in either the laboratory or factory environment. However, because of the need for clean power supplies and an RF shielded environment, most of these techniques are not applicable to on-line equipment. Consequently, recourse must be made to the detection of other signals (related to partial discharges) which are not electrical in nature. The most useful of these signals have proven to be the high frequency mechanical stress waves (acoustic emissions) introduced into the surrounding material by a partial discharge source. Using modern signal detection and manipulation techniques, it is possible not only to detect the existence of these signals but also in many situations it is possible to locate the geometric position of the PD source itself. Although these techniques were originally developed for use on operating power transformers, the technology also shows promise for use in evaluating other devices such as capacitors, bushings, and cables, etc.