Characteristics of phase resolved partial discharge pattern in spherical voids

Prior experience shows that partial discharges in small spherical voids embedded in dielectric material are leading to regular phase resolved partial discharge (PRPD) patterns. A study was carried out with artificial spherical voids. Consecutive PRPD patterns were recorded with the (transparent) voids covered or exposed to UV light, while the voltage was increased stepwise. At present a second study covers the recording of consecutive PRPD patterns originating from treeing within short samples of medium voltage cables. With this study the voltage is kept stable, while the consecutive patterns are being recorded during the evolution of the electrical tree. A special PC program provides a quick-motion replay of the PRPD-pattern recorded previously. This quick-motion replay allows the evaluation of the evolving discharge characteristics. The influence of the relation between actual electrical field and inception field or the impact of ionizing radiation, for instance, can be studied easily by means of this movie-like replay.