Recent progress of high field conduction and breakdown in insulating polymers

Reviews the results of research on electrical conduction and breakdown in polymer solids which have been reported mainly since the 1980s, and comments on the present situation and future prospects of research in this field. Among the topics discussed are polar polymers, avalanche, prebreakdown, morphology and chemical structure, space charge, and localized heat generation. It is noted that, from the viewpoint of technology, it is important how the fundamental electric properties can be related to electrical insulation technology in practical apparatuses. For instance, the effective thickness of insulation used in actual 500-kV XLPE cables is 32 mm so that the average electric field reaches about 13 kV/mm. The electric stress considered in the design of XLPE increases as the operating voltage increases; higher operating voltage requires higher reliability of the insulation system