A comparison of streamer and partial discharge inception voltages in liquid dielectrics

Various investigations have concerned themselves with the inception of prebreakdown streamers in liquid dielectrics. Others have focused on the inception of partial discharges under non-uniform field conditions. While the first group used mainly simple liquids such as n-hexane, toluene, poly (methyl siloxane) or transformer oil, the latter group utilized more practical fluids which are commonly used in industry. Because of this situation it is difficult to compare published data reflecting streamer initiation with those of partial discharges. To provide such comparison a study of three commercial liquids was undertaken and the results of this study are reported here. It is shown that the inception voltages for streamers and partial discharges are reasonably similar. It is suggested that the two phenomena are interrelated. The relationship between them is discussed in detail.