Influence of metallic materials on the generation characteristics of decomposition products of SF6 high-energy discharge faults

High-energy discharges are the main cause of inducing sudden failures in gas-insulated switchgear (GIS) equipment. This paper focuses on the decomposition of SF6 gas under high-energy discharge, focusing on the influence of metal materials (stainless steel, aluminum and copper) on the generation characteristics of SF6 decomposition products under controlled high-energy discharge (0.25 Hz, 10 800 cycles), and analyzing the gases and solid products by combining the techniques of gas chromatography-mass spectrometry and X-ray photoelectron spectroscopy (XPS). The results show that different metallic materials have a significant effect on the generation of decomposition products: the generation of CF4 is driven by carbon impurities and the composition of the electrode materials, following the rule of Fe > Cu > Al; whereas the generation of sulfur-containing products (SOF2, SO2F2, SOF4, and SO2) exhibits the pattern of Al > Cu > Fe, which is attributed to the exothermic heat of fluorination of the different metallic materials under high-energy discharge faults, differences in the escape work and the oxide layer of different metallic materials. The production of SOF2 and SOF4 increases linearly with the number of high-energy discharges, while SO2F2 and SO2 increase exponentially, reflecting competing pathways in the SF4 hydrolysis and oxidation reactions. XPS analysis of the solid residues showed Al/W > Cu/W > Fe/W molar ratios, confirming that Al reacts to the highest extent with SF6, producing mainly AlF3 and Al2O3, while Fe and Cu mainly produce FeF3 and CuF2/CuO. This study provides an important guideline for the optimization of electrode materials for GIS and the development of decomposition-based diagnostic strategies for high-energy discharge faults.