# Internal Partial Discharge and Breakdown Characteristics of Thin Polypropylene Films

Shobha, R and Nema, RS (1993) Internal Partial Discharge and Breakdown Characteristics of Thin Polypropylene Films. In: Conference on Electrical Insulation and Dielectric Phenomena, 1993. Annual Report, 17-20 October, Pocono Manor,PA, pp. 408-413.

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One of the major causes of failure of polypropylcne(PP) film high voltage capacitors is PD (partial discharges). PD can occur in the cavities or gas pockets formed due to variation in tightness of windings, improper impregnation and swelling of the film due to its interaction with the impregnating fluid. The effect of pressure and radial dimensions are important in small cavities mostly because system impregnation is done at low pressures and the cavity size gets reduced .It is probable that with time the cavity pressure will equilibrate with that of the surrounding ambient medium due to diffusion process. An attempt is made here to study the effect of cavity dimensions such as diameter (0.9 mm to 3.2 mm) and depth (40 $_\mu$m to 200 $_\mu$m) on the various PD characteristics and the related breakdown of thin PP films.