Abstract: During the annual maintenance of the condenser in a converter station, it was found that the DC resistance of the rotor exceeded the standard. Therefore, the defects of the joints and connecting parts involved in the rotor conductive circuit are located. It is determined that the DC resistance of the conductive screw on the side of the inner collector ring exceeds the standard. After that, the part shall be disassembled for inspection and defect elimination. After reassembly, the DC resistance of rotor is qualified. After the annual maintenance of the camera, the camera is smoothly connected to the network. It ensures the stability of reactive power support for DC system.