Evolutionary Mechanism and Damage Characteristics of “Gel–Solid” Creeping Discharge of Power Device Package Insulation Under Coupled Temperature–Frequency Effects

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.