Abstract: This paper analyses the reasons fracture and collapse of porcelain bushings of phase A lead wires and surge arresters in a 220kV GIS (Gas Insulated Switch-gear, GIS) in a wind farm substation. By investigating the inspection, process regulations and operation instructions from the manufacturer, and conducting on-site investigations, the reasons for the fracture of the 220kV GIS A phase lead-out porcelain sleeve and the A-phase arrester porcelain sleeve were found. According to the analysis, the reason for the fracture is that the two porcelain bushings had manufacturing quality problems. Concentration of local mechanical stress at the installation site had caused microscopic cracks in the insulating ceramic material or fracture of the ceramic sleeve. There is a large uneven thickness of the cement bonding surface at the fracture of the lower section of the porcelain sleeve of the phase A arrester (the difference in the thickness of the bonding surface is 5.05mm). This causes eccentricity of the porcelain sleeve, and therefore local stress concentration is formed at the root of the porcelain sleeve. The porcelain sleeve of the A-phase arrester breaks under the tensile force generated when the GISA-phase outlet casing breaks and collapses.