Phase resolved PD patterns in treeing in the presence of voids

One of the important aspects of insulation condition monitoring through partial discharge (pd) detection is the need to establish a trend in the discharge pattern for a given insulating system. Treeing is one of the principal routes to failure in insulating materials, and its growth is accompanied by pd activity. In this work, a study of the evolution of the phase resolved pd patterns during the various stages of tree growth in the presence of void is undertaken. Air-filled artificial voids are injected into the polymer, and their effect on the growth of a pre-existing tree observed. The pd patterns were seen to change drastically on tree channels reaching the void. The tree channel reaching the void was seen to undergo intense pd activity followed by widening of the channel. Electrical pd detection is performed simultaneously with online visual observation of tree growth with a high resolution high speed camera.