Effect of impregnation, compression and temperature on electric strength of polythene and polypropylene

Some Factors Affecting the Breakdown Strength of Solid Dielectrics: A Short Review

“…They showed that the AC breakdown strength as well as the partial discharge behavior improved [28]. In [15], DC and impulse breakdown strength of polypropylene increased by impregnation with suitable dipolar The breakdown strength of polythene impregnated with chlorinated diphenyl was also found to increase at room temperature under impulse conditions.…”

“…On the other hand, swelling of a polymer -in case of impregnation with liquidmay be reduced by some factors such as crystallinity. Authors in [15] reported that the breakdown strength of both polythene and polypropylene depends mainly on their semi-crystalline structure and the presence of defects rather than their chemical structure, since the two polymeric materials have similar values of breakdown strength. The preponderant role of defects was also emphasized in [16,17], since defects can vary from those of molecular dimensions up to gross defects arising from inclusions.…”

“…About four decades ago, it was shown that both DC and impulse breakdown strength of polythene increased by compression. The effect of changing from an uncompressed to a compressed sample was an increase of 38% in the mean breakdown strength (from 0.61 to 0.84GV/m) [15]. Indications of the influence of mechanical stressing on the breakdown strength of polythene were given even earlier, when it was noted that its impulse strength at 80 o C was much higher than the breakdown strength of the same material tested under the same temperature with a slowly applied electric stress [79].…”