Correlation Between Partial Discharge Parameters Measured by UHF, IEC and HFCT Methods

Partial discharge signal amplitudes measured using a UHF sensor are correlated with peak charge and average discharge power measured using the standard IEC and HFCT methods. Two common types of partial discharge, surface discharge and cavity discharge, are simulated in the laboratory with different insulation materials in air environment. The results show that for the surface and cavity discharge, there is strong correlation between the UHF signal amplitudes and the peak apparent charge and discharge power over an applied voltage between 1.1 and 1.6 times the partial discharge inception voltage, with a linear relation linking the discharge parameters. The pulse repetition frequency measured with the UHF method for the case of surface discharge shows a strong correlation with those measured with the IEC and HFCT methods, and is related to them through an exponential function, whereas a linear model can be used to link these discharge parameters for the case of cavity discharge. At higher voltages, the correlation between the UHF data and the data obtained by the IEC and HFCT methods becomes weaker, presumably due to different discharge processes occurring at these voltages.