Abstract
The current time domain spectroscopy of dielectrics provides important information for the analysis of dielectric properties and mechanisms. However, there is always interference during the testing process, which seriously affects the analysis of the test results. Therefore, the effective filtering of current time domain spectroscopy is particularly necessary. L1 trend filtering can estimate the trend items exactly in a set of time series. It has been widely used in the fields of economics and sociology. Therefore, this paper attempts to apply L1 trend filtering to the current time domain spectroscopy. Firstly, polarization and depolarization currents are measured in the laboratory. Then the test results are filtered by L1 trend filtering and the filtering effects are compared with several common filtering algorithms, such as a sliding mean filter and Savitzky–Golay smoothing filter. Finally, the robustness and time complexity of L1 trend filtering are analyzed. The filtering results show that because the polarization currents vary in a wide range of the time domain (about 2–3 orders of magnitude), smooth and undistorted curves in the whole test time range can hardly be obtained through common filtering algorithms, while they can be obtained by L1 trend filtering. The results of robustness analysis and time complexity analysis show that L1 trend filtering can extract the trend items accurately in the time series under given different noise levels, and the execution time is also lower than 176.67 s when the number of tested points is no more than 20,000. Those results show that L1 trend filtering can be applied to the time domain current spectroscopy of dielectrics.
Highlights
The time domain spectrum of insulating dielectric current refers to the currents flowing through the insulating dielectrics during the application of a step voltage and short circuit, which are called polarization currents and depolarization currents, respectively
The filtering results show that because the polarization currents vary in a wide range of the time domain, smooth and undistorted curves in the whole test time range can hardly be obtained through common filtering algorithms, while they can be obtained by L1 trend filtering
The Filtering Results with L1 Trend Filtering Algorithms. Since this is the first time that a L1 trend filter has been applied to the time domain spectrum of. Since this is the first time that a L1 trend filter has been applied to the time domain spectrum of the polarization currents, there is no reference to determine the reasonable range of the regularization the polarization currents, there is no reference to determine the reasonable range of the parameter λ
Summary
The time domain spectrum of insulating dielectric current refers to the currents flowing through the insulating dielectrics during the application of a step voltage and short circuit, which are called polarization currents and depolarization currents, respectively. Macroscopic parameters (conductivity, dielectric constant, and loss factor) and microscopic parameters (polarizability, space charge) can be obtained by polarization and depolarization currents, and the corresponding internal microstructures can be inferred. Most scholars have applied polarization and depolarization current to the diagnosis of insulation aging state. By equivalent the dielectric to the extended Debye model, the model parameters are solved according to the measured current results. The relationship between the model parameters and aging state is analyzed to judge the aging degree of insulation [9,10,11,12,13,14]. It is very important to obtain accurate polarization and depolarization currents for dielectric properties and aging state analysis
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