Life Time Enhancement and Partial Discharge Performance of SiC Reinforced Polyimide Nanocomposite Insulations Under High-Frequency Electric Stress

The growing demand for renewable energy is driving advancements in power electronic devices, such as solid-state transformers (SSTs), where a reliable insulation system is critical for safe operation. SSTs are often exposed to prolonged high-frequency voltages, increasing the risk of insulation failures. However, research into the high-frequency insulation performance of polyimide (PI) materials requires further attention. This study investigates the incorporation of silicon carbide (SiC) fillers into a PI matrix and evaluates their effects on the insulation properties of PI films. Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) results demonstrate excellent dispersion of SiC within the polyimide matrix. The results show a significant improvement in the high-frequency breakdown characteristics and time of SiC-modified PI composites compared to pure PI films. Additionally, both surface and volume resistivity increase with higher SiC doping levels. The changes in dielectric properties are attributed to reduced permittivity and polarization loss. While exposure to high-frequency voltages can lead to heat buildup within the films, the reduction in dielectric loss mitigates this heat accumulation, resulting in less surface deterioration. An increase in SiC content is associated with a decrease in partial discharge (PD) amplitude and mass loss percentage of the composites. Notably, the PD performance and breakdown characteristics are optimal at a 15% SiC/PI composition. These findings offer a promising approach to develop polyimide-based insulation with improved high-frequency insulation performance.