Investigation on the Generation Characteristics of Carbon Particles in Insulating Oil Under Discharge Energy

Particulate contamination in insulating oil is a key hidden hazard that affects the dielectric performance and operational reliability of oil-immersed power transformers. Among these, carbon-based particles generated from the decomposition of insulating oil under electrical and thermal stresses are a significant source. Although external contaminants and cellulose aging products have received considerable attention, there is still a lack of quantitative understanding of the systematic characteristics governing the formation of solid products from the self-decomposition of insulating oil driven by discharge energy. In this study, the generation behavior of carbon particles in naphthenic mineral insulating oil under different discharge energy levels was systematically examined, with a focus on analyzing the variation characteristics in particle quantity, size distribution, and morphology. The results showed that, under the experimental conditions, particle quantity exhibited a significant positive linear correlation with discharge energy. The particle size distribution was independent of discharge energy, with micro-sized particles below 5 μm constituting the majority of the carbon particles. Additionally, the regularity of particle morphology increased with discharge energy. This study quantitatively reveals the core characteristics of carbon particle generation from the self-decomposition of insulating oil driven by discharge energy, providing new experimental evidence and theoretical support for assessing the severity of internal discharge faults in transformers and for early warning of insulation risks.