Behavior of Partial Discharges in Mineral Oil with Solid Dielectric Barrier under Long-Term AC Voltage

The main purpose of the presented research is to investigate the variability of partial discharge (PD) phenomenon under long-term AC voltage with particular consideration of the selected physical quantities changes while measured and registered by electrical method. During the research a PD model source generating surface discharges is immersed in the brand new mineral insulation oil. There is a solid dielectric barrier made of 8mm thick Teflon (PTFE) applied in the research. The PD source is powered by the AC voltage with its relative level of 1.3 of the inception voltage (U-i) of the PD source within 168 hours. A conventional electrical method is applied for measurements on the signals generated by PDs. Signals generated by the continuously occurred PDs within 168 hours are registered. Various qualitative as well as quantitative indicators that describe the PD variability in time are assigned. Furthermore some long-term characteristics of the applied PD model source in the mineral oil are also presented. Finally various statistical tools are applied for the results analysis and presentation. According to the presented research from among all assigned indicators there are discriminated descriptors that depend as well as not depend on PD long-term duration. On the grounds of the regression models analysis there are discovered trends that potentially allow to apply the results for modeling of the PD variability in time