Abstract:There are limitations in using common ultra high frequency method, ultrasonic method and high frequency current method individually to detect internal discharge in transformer. At the same time, the large electromagnetic environment interference of substation, continuous vibration interference during the operation of transformer, and its metal closed structure cause the low success rate of detection and location of internal partial discharge. A joint positioning method is proposed, that is, acoustic and electrical joint positioning method with high frequency current and ultra high frequency joint positioning, which can accurately judge the failure of internal discharge in 500 kV transformers. The disassembly inspection of the transformer after returning to the factory is completely consistent with the results of on-site positioning, which verifies the effectiveness of the proposed method.