Common faults of Oil-immersed transformer in operation include winding, bushing, tap changer, core, oil tank and other accessories. Winding fault There are inter-turn short circuit, winding grounding, inter-phase short circuit, wire breakage and joint open welding. Casing failure Transformer bushing scaling causes pollution flashover in fog or light rain, which causes single-phase grounding or inter-phase short circuit on high voltage side of transformer. Serious leakage The oil leakage of transformer is serious or continuous from the damaged part so that the oil level gauge can not see the oil level. At this time, the transformer should be stopped to repair and refuel immediately. The causes of oil leakage of transformer include cracking of welding seam or failure of sealing parts, serious rust and damage of oil tank caused by shock external force in operation. Tap changer Common faults include poor contact or inaccurate position of tap changers, surface melting and b