DC conduction in polymeric insulation

The importance of polymeric insulation in the electrical industry is shown by the many hundreds of published papers concerning the AC electrical conduction (or dielectric loss) of such materials. In contrast, not much attention has been given to the study of DC conduction with which we shall be exclusively concerned in this paper. Difficulty in the interpretation of the DC measurements is primarily responsible for this; however, some progress has been made in this direction and the present state of the art will be summarized in this paper.