22-09-2017, 11:06 AM
Internal discharges into cavities in solid dielectric materials lead to degradation, deterioration and complete failure of insulating materials. This would shorten the life of electrical equipment, which affects the reliability of the power supply. This research is a research and study of internal discharges, such as magnitude and energy, into micro-cavities in solid dielectric samples. The field distribution in these cavities was simulated, modeled and calculated for some applied voltage. Alternating the high voltage at the power frequency at room temperature was applied with different values of the initial voltage of the sample. The shape of the cavity, cylindrical and spherical, and its dimensions were changed, with the cross-sectional area of the cavity much larger than its depth. The cavity size was much smaller than the sample thickness. The study was carried out on low density polyethylene (LDPE), polyvinyl chloride (P.V.C) and ethylene polypropylene rubber (E.P.R) due to its important industrial applications. The location of the cavity w.r.t la h.v. electrode in the dielectric sample was changed, to be in the center, adjacent to the h.v. electrode and near the ground electrode. The number of cavities was changed from one to three, either horizontally or in vertical or random formation in the sample. The permittivity of the dielectric ratio was changed from 2 to 10. The field distribution and its improvement within the cavity were calculated using a program developed using the boundary element technique. The magnitude of the field within the cavity was significantly increased by increasing the relative permittivity of the dielectric, its magnitude was expanded for the cavities adjacent to h.v. electrode.