The most characteristic features of the processes of electrical filtration of ideal and low conducting dielectric fluids are considered. It is noted that, in liquid dielectrics in highly inhomogeneous electric fields, phenomena similar to those at corona discharge in gases with all its consequences are observed. The processes of electrical purification (separation) are interpreted in terms of a corona discharge. In particular, the electric charging of dispersed particles and their transport to the “electrode–collector” are considered. The threshold phenomena at electric separation such as the appearance and disappearance of the separation effect are treated from the standpoint of a corona discharge as well. Two concepts, namely, the screening of an external electric field by the field’s spatial electric charge and the ohmic resistance of the layer of dispersed particles deposited on the collector are discussed. Both approaches lead to identical results. To clarify the above mentioned theoretical concepts and to work out recommendations for the modernization and efficient use of electrical separation, further studies of the experimental time–current characteristics of the process of the separation are needed.