To improve the reliability and quality of electric power systems, preventive diagnosis and regular maintenance of high voltage capacitors are required. Dielectric response measurements in both time domain and frequency domain are potential tools for assessing the condition of dielectric of high voltage capacitors. Modern measurements in time domain include polarisation and depolarisation current (PDC) and recovery voltage (RV) measurements, whereas frequency domain measurements include dielectric dissipation factor (DDF) measurements. To understand the physical behaviour due to the effect of moisture and aging, a detailed analysis of dielectric test results is required. In this paper, a detailed equivalent circuit model of the insulation system in high voltage capacitors has been given. The values of the parameter of the circuit model have been calculated from the dielectric test results. Correlation between the physical condition of the insulation and the equivalent model parameters are also presented in this paper.
Keywords: polarisation and depolarisation current, PDC, recovery voltage, dielectric dissipation factor, DDF, dielectric response, Debye model, high voltage capacitor, oil-paper insulation, condition monitoring, aging, power energy