Some Experimental Factors Affecting the Insulation Life of Polypropylene Films for Power Capacitors

Abstract

In capacitors and cables, polypropylene (PP) in film form is usually used as dielectric material and insulating material. Obviously, under the combination of high electric field and thermal stress, materials’ ageing and even failure are inevitable when the equipment runs for a long time. Previous studies have shown that the insulation characteristics of PP polymer dielectrics are mainly related to temperature and electric field strength. However, different electric field types and electric field uniformity also significantly affect the insulation performance of PP materials. In this paper, the insulation performance of polypropylene film samples was tested by changing the experimental factors such as electric field intensity, electric field unevenness, temperature and electric field type under the control of other experimental conditions. The experimental results show that the failure time of PP polymer decreases with increasing electric field strength, electric field uniformity or temperature. Electric field and temperature play essential roles in polymer ageing and decomposition. Unlike the results under AC voltage, PP film has longer decomposition time under the DC field and is less sensitive to temperature. In addition, the morphology of the samples was observed by the magnifying glass to illustrate the decomposition mechanism.