Prebreakdown phenomena in liquids: propagation 'modes' and basic physical properties

Prebreakdown phenomena in liquids (usually called 'streamers') were characterized experimentally in a wide range of experimental conditions, liquid nature and additives. The description of these phenomena leads to a complex and frequently confused situation, since their properties widely vary when parameters such as liquid nature or voltage are changed. In this review paper, we try to obtain a more comprehensive presentation of pre-breakdown phenomena in liquids by considering different propagation 'modes', which can be recognized in a wide range of liquid nature and experimental conditions. On the basis of experimental results either published previously or original, we will review the main parameters and features able to better characterize these modes, and show their general interest. 'Positive' streamers observed in point-plane geometry in non-polar liquids are mainly considered here. Some elements allowing a comparison with water, characterized by a much higher permittivity and conductivity are given. The text is concluded by considerations concerning the different physical processes involved in modes.