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The resolution performance of space charge measurement method determines its application environment and measured information, which has put forward higher temporal and spatial resolution requirements for the charge evaluation of electronic equipment insulation. Based on the ellipsometry detection principle and the photoelastic effect of the sensor, a novel optical method for space charge measurement is proposed. The potentials of the method in terms of single measurement with high signal-to-noise ratio, terahertz bandwidth and nanometer spatial resolution are analyzed. By deriving the mathematical relationship of the signal transmission, it is indicated that the light intensity difference measured by the system can linearly present the elastic force generated from space charge. Based on the built ellipsometry detection system, it is found that the detected signal from the sensor can quickly track the imposed elastic waves with different amplitudes and frequencies, which verifies the feasibility of the crucial detection part and the fast measurement speed of the proposed method. Further simulation results indicate that the refractivity performance of the sensor under the effect of elastic waves can present the deformation variation with a spatial resolution of 2 nm. Therefore, the given explorative research can provide the key theoretical basis and experimental verification for the proposed method.

This paper focuses on the effect of unipolar and bipolar square, sine and triangle voltages on space charge characteristics inside solid insulation based on the bipolar charge transport model. According to the model solution process and the polarization characteristics, it is found the algorithms for the model should be chosen with regard to the direction of the electric field at each subdivision inside the calculation sample. Further comparison shows that the charge amount under different conditions is mainly determined by the input power of the imposed voltage, while the migration depth of the injected charge is less than 20 μm from the sample surface. Correlation between the current injection and the charge amount indicates that the variation trends of them follow basically the same. The results under unipolar conditions are not affected by the frequency provided it is larger than 10 Hz, while the charge amount under bipolar ones is negatively correlated to the frequency. Meanwhile, the impact of the initial phase of bipolar polarization decreases rapidly with the increased simulation time. Hence, for space charge measurement inside dielectrics under such conditions, a reliable system should be established according to the polarity and waveforms of the polarization.

This paper reports the effect of DC and pulse wave voltages on space charge characteristics of polyimide material for high-frequency insulation. The pulsed electroacoustic method is used to measure the charge distribution inside the material under the pulse wave voltages with different amplitudes, polarities, frequencies and duty ratios. Comparative results show that positive charge is more likely to accumulate inside the polyimide. The amount of accumulated charge under pulse wave voltages is larger than that under DC voltages. With frequency, more space charge is accumulated under negative pulse wave voltages with a frequency above 50 Hz, while it is not larger than 100 Hz under positive voltages. The maximum distortion of electric field appears under the negative pulse wave voltage with the frequency of 500 Hz, which is 1.19 times the applied field strength. When the duty ratio of the pulse wave voltage exceeds 50%, the distribution of accumulated charge tends to be stable. The research results can provide a reference for the practical application and modification design of polyimide materials in power electronic equipment.