PD detection and localization by means of acoustic measurements on hydrogenerator stator bars

Acoustic partial discharge detection appears useful for the location of PD sources within various kinds of insulating systems. The usefulness of such a method to locate discharge sources in hydrogenerator stator bars is illustrated. The adopted measuring procedure, based on two piezo-electric transducers positioned on a bar, allows the identification of the discharge site position within an error range of ~2 cm. Such a measuring procedure appears useful as a diagnostic tool in quality control for bars that do not pass the specified acceptance test or in the development of new insulating systems. The measurement circuit and the relevant test procedure are presented. Further comments about the measured acoustic velocities of the acquired signals are given