Study on the Relationship Between Self-Healing Properties and Insulation Performance: From Metallized Films to Devices

Metallized polypropylene film capacitors (MPPFCs) are commonly used in high dc transmission systems due to their self-healing capabilities. This study investigates the impact of the self-healing process on insulation performance, from both the film and device perspectives. To quantify these effects, custom-built measurement platforms were used to assess leakage current and insulation resistance (IR) in both metallized films and capacitors. The results show that as the number of self-healing events increases, the insulation performance of both the film and the capacitor decreases to varying degrees. Additionally, a microscopic analysis revealed significant carbon accumulation in the self-healed areas. Simulation of the carbonization process at a single self-healing point showed that at 8.4 kV, carbonization leads to a 68% decline in insulation performance at the self-healing site, closely matching experimental results. This confirms that the formation of carbonized channels during the self-healing process under high electric fields is the primary cause of increased leakage current and reduced IR. Based on these findings, a theoretical model of self-healing and carbonization was developed, uncovering the fundamental mechanisms behind the degradation of MPPFC insulation performance. This provides a theoretical foundation for the design and improvement of future high-reliability power electronic components.