Space charge observation under periodic stress — Part 2: Signal improvement and corresponding procedure

Several signal processing methods are introduced to improve the signal detected under periodic stress in terms of the signal-to-noise (S/N) ratio and behaviour in an arbitrary phase. In the filtering process for the averaging and fitting methods, it is assumed that the variation of space charge can be neglected for a given detecting phase. The averaging process is associated with the phase identification under periodic stress. The fitting process is shown to further enhance the S/N ratio based on space charge behaviour at different positions. A fitting model is chosen based on the signal characteristics, such as the dynamic response of the charge signal and the voltage waveform in the excitation source. The process is based on the premise that the space charge distribution can be detected without significant mutation near the interpolation phase. The procedure proposed optimises signal processing that is associated with space charge.