Jingrui Wang

In order to improve the effectiveness of partial discharge detection in attached metal particle insulators, this paper proposes a partial discharge detection method for particle defects in insulators under high-frequency sinusoidal voltage excitation. In order to study the development process of partial discharge under high-frequency electrical stress, a two-dimensional plasma simulation model of partial discharge with particle defects at the epoxy interface is established under plate–plate electrode structure, which realizes the dynamic simulation of particulate defect partial discharge. By studying the microscopic mechanism of partial discharge, the spatial and temporal distribution characteristics of microscopic parameters such as electron density, electron temperature, and surface charge density are obtained. Based on this simulation model, this paper further studies the partial discharge characteristics of epoxy interface particle defects at different frequencies, and verifies the accuracy of the model from two aspects of discharge intensity and surface damages through experimental means. The results show that with the increase in the frequency of applied voltage, the amplitude of electron temperature shows an increasing trend. However, the surface charge density gradually decreases with the increase in frequency. These two factors make partial discharge severest when the frequency of the applied voltage is 15 kHz.

In outer space’s extreme electron radiation environment, the insulating medium will experience a deep dielectric charging effect. As an excellent insulating medium, polyimide is widely used in spacecraft. In practical use, glass microspheres and glass fibers are often added to increase its mechanical strength. However, the influence of glass microspheres and glass fibers on deep dielectric charging effects has often been ignored in previous studies. Therefore, the work in this article established a 3-D deep dielectric charging model of glass microsphere and glass fiber reinforced polyimide. Using the model, the effects of glass microsphere and glass fiber volume fraction, glass microsphere spacing, glass fiber orientation, and 3-D glass fiber structure were investigated. The results show that the larger the volume fraction of glass fiber or glass microsphere, the more obvious the decrease of polyimide composite media’s average electric field strength. Under the same volume fraction, glass fibers are more favorable to reduce the average electric field strength than glass microspheres. The surface of glass microspheres will form charge accumulation, increasing local maximum electric field intensity, which is greater than the maximum electric field value of pure polyimide under electron radiation. When the spacing of glass microspheres decreases, the degree of electric field distortion increases, but the electric field value decreases when the microspheres contact each other. When the glass fiber orientation is perpendicular to the ground plane, it can better provide the electronic release channel, thereby reducing the deep dielectric charging effect. Using 3-D glass fiber structures can reduce the polyimide’s average electric field value and reduce the maximum local electric field distortion.

When DC GIL in operation endures the lightning impulse voltage, the charge accumulation at the gas-solid interface area will seriously affect the insulation performance of the spacer. Considering that gas side conduction is one of the important factors affecting charge accumulation, for the purpose of clarifying of the insulation characteristics of gaseous medium in the flashover process of gas-solid interface, an experimental platform for simulating the working conditions of the spacer is built. The spacer flashover tests were carried out with and without aluminum particle in SF ₆ , 4% C ₃ F ₇ CN /96% CO ₂ and 20% SF ₆ /80% N ₂ gas mixture. The measurement and analysis of surface potential distribution behavior of the spacer was conducted. The experiment results show that the gas dielectric is not the factor which dominate the potential distribution process without aluminum particle, and there is little difference in potential distribution with various gaseous conditions. When the linear aluminum particle appears on the surface of the insulator, it will cause severe electric potential distortion and these potential distorted areas are located around the end of the metal particle near the central conductor, and along with flashover pathway. It has also demonstrated that the gaseous dielectric has influence on the surface charge accumulation behavior especially with metallic particle adhere to spacer surface. Under the C ₃ F ₇ CN/CO ₂ gas mixture, the surface flashover voltage decrease percentage is about 16.82% and may be lower. Besides, the insulation strength of the gaseous dielectric itself is also a key factor affecting flashover.