Electric tree is a dendritic channel due to partial discharge, which is a more common form of failure in the insulation system of power electronic modules, and silicone gel is widely used in the package insulation of power electronic modules. On this basis, this paper conducts experiments on the growth of electric trees at different frequencies, investigates the initiation and propagation mechanisms of electric tree in silicone gels at high frequencies, and analyzes the mechanism of the effect of frequency on the growth characteristics of electric trees. Furthermore, the self-healing experiments of electric trees at different temperatures and component ratios were carried out to investigate the self-healing behavior of electric trees in silicone gels and its influence mechanism. The experimental results show that Maxwell stress is the main cause of electric tree initiation at high frequencies, and the propagation characteristics of electric trees in silicone gels are different from those of conventional dielectrics. Self-healing in silicone gels can be classified into types I and II, which occur respectively during electric tree propagation and after withdrawal of voltage, and type II self-healing can be further classified into physical and chemical self-healing. The effects of temperature and A-component content on the self-healing properties are also investigated in this paper.

The multienergy conversion equipment power devices are prone to form creeping discharges at silicone gel and ceramic substrate interface. This article investigated the influence mechanism of coupled temperature–frequency effects on the creeping discharge of “gel–solid” insulation and the surface damage characteristics of the ceramic substrate. The results showed that the partial discharge initial voltage (PDIV) was independent of the change in frequency but decreased by about 35% as the temperature increased (20 °C–120 °C). The maximum discharge amplitude and pulse repetition frequency increase and then decrease with the increase of frequency, and the phenomenon of “frequency-induced inflection point” occurs around 20 kHz; it increases with the increase of temperature, and the increase of temperature has a certain weakening effect on the phenomenon of “frequency-induced inflection point.” With the aggravation of surface damage and the generation of products in different discharge stages, the surface conductivity showed a gradual upward trend. The analysis concluded that the coupled temperature–frequency effects significantly affected the development of creeping discharge, the interfacial charge distribution and the material’s dielectric properties determined the gel–solid creep discharge evolution mechanism, and the damage characteristics of the substrate mainly determined the creeping discharge pattern.

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.

To improve the ranging accuracy and reliability of high-resistance grounding faults in 35 kV high-voltage distribution networks, a ranging method based on smoothed pseudo wigner-ville Distribution is proposed to locate the fault position. Firstly, analyze the transmission characteristics and frequency features of the traveling wave of the distribution network fault, and generate the time-frequency characterization spectrum. Then, by improving the projection analysis method, the raised areas on the frequency axis of the image are determined and the resolution on the time axis is enhanced. Finally, the peak detection method is used to determine the coordinates of the fault location in the image, and the specific time when the traveling waveguide arrives at the measurement point is calculated, thereby determining the actual fault location. A 35 kV distribution network model was built using PSCAD. The verification through numerical examples shows that the proposed method can achieve high-precision positioning of high-voltage distribution lines and improve the sensitivity and robustness of the high-resistance grounding fault distance measurement method.