Optimization of Space Charge Electro-Optical Detection System in Power Electronic Insulation: Toward High Sensitivity

For high-resolution measurements of solid insulation space charge in complex stress environments, an optical measurement method of space charge based on the electro-optical effect is proposed. In this article, the whole process signal conversion mechanism and transmission model of the space charge electro-optical detection system are constructed. Furthermore, the key factors affecting measurement sensitivity are analyzed for the core electro-optical detection system. The results show that the measurement sensitivity shows a positive and negative correlation with the sensor electro-optical coefficient and sensor thickness, respectively. Simultaneously, it shows a decreasing trend in measurement sensitivity as the angle of incidence deviates from the Brewster angle of the electro-optical sensor. The optimal configuration of the measurement sensitivity can be realized by adjusting the incidence angle of the detection light, the electro-optical coefficient, and the thickness of the sensor. Expanding the measuring bandwidth further decreases the signal distortion. The detector bandwidth is the primary parameter that limits the behavior of the detecting system. Ultimately, a refined design for the electro-optical detecting system is suggested for sensitivity improvement. The significant sensitivity is obtained by incorporating the optical sampling technique. The experimental results demonstrate that the established detection system is capable of accurately measuring the picosecond pulsed electric field. The enhanced electro-optical detection system achieves measurement sensitivity at the $\mu $ V level and bandwidth in the THz range. The space charge measurements with nm resolution can be realized through the proposed detection system.