Step propagation of filamentary streamers in dielectric liquids

By considering the streamer filament as a cylindrical channel, we evaluate the electrical charge at its head and the local electric field. We further discuss the mode of the propagation of the streamer, i.e. by steps or continuous. The order of magnitude of the charge associated with each step of propagation is in satisfactory agreement with experimental data. The partial displacement corresponding to each step of propagation is under the dependence of the local electric field. The streamer velocity for each step of propagation increases when the charge and/or the voltage increase. Since the values of elementary charges are nearly equal when the streamer propagates in the first half to the two-thirds of the electrode gap, the local electric field remains nearly constant, and the corresponding partial displacements will be constant. Therefore, the propagation appears as constant even the streamer propagates by steps. Moreover, the more conducting the streamers, the faster they are. The occurring mechanisms are also discussed. In closing, we discuss the role of space charges in the propagation of streamers