A study on partial discharge degradation of polypropylene films

Abstract

One of the major causes of failure of polypropylene (PP) film high voltage capacitors is PD (partial discharges). PD occurs in the air gaps in the inter layer spaces present due to variation in tightness of windings. It is also possible that the air gaps present may be at different sub-atmospheric pressures due to vacuum impregnation. Therefore it becomes essential to undertake PD studies at pressures below atmospheric. An attempt is made here to study the PD degradation (on the basis of electric strength measurements) of PP films in short term ageing tests at pressures of 500 and 250 mm Hg in dry air.