Reconstruction of Partial Discharge Waveform in Mock Simulated of Insulation Joint by Deconvolution Processing

The partial discharge measurement in the cable is usually carried out by electrically connecting the detector at the terminal or insulation joint. The system has a complicated transfer function from the discharge point to the measurement point. The observed waveform is a convolution of the transfer function and the partial discharge waveform at the discharge point, resulting in a distorted waveform. On the other hand, the waveform characteristics of the partial discharge reflect the electron avalanche process in the discharge space. It may be possible to estimate the condition of defects based on the waveform characteristics. In this study, we constructed the mock model of the insulation joint and reconstructed the partial discharge waveform at the discharge point by deconvolution processing. To obtain the transfer function, it is necessary to input a known pulse and analyze its response. In a cable at a site, it is difficult to input the pulses because the sheathed terminals of the insulation joint are insulated with an insulation coating to ensure system reliability and safety. Therefore, the transfer function was obtained by measuring the impedance from the detector side and analyzing the equivalent circuit. The validity of the transfer function was shown in comparison with the transfer function when directly inputting the pulse to the discharge point. The characteristics of the reconstructed waveform were almost the same regardless of the acquisition method of the transfer function. Furthermore, the difference in the discharge points simulated deterioration can be found based on the characteristics of the reconstructed waveform.