Study on the distribution of thermal field in the valve-side bushing with internal crack defects of UHV converter transformer

The valve-side bushing of the converter transformer is the core component of the HVDC converter transformer, and the internal crack defect of the bushing will affect the operation of the bushing. A 3-D finite element simulation model of the valve-side bushing with the internal crack defect is established, and the thermal field distribution of the valve-side bushing is calculated when the dynamic parameters are continuously changed. The thermal field distribution law of the valve-side bushing under the change of dynamic parameters is compared and analyzed, and the influence of valve-side bushing connection failure and internal crack defects on the internal thermal field distribution and thermal characteristics of the valve-side bushing is discussed. Finally, it is concluded that the cracks in the inner conductor will cause overheating of the bushing, and the cracks in the solid medium such as capacitance core will cause electric field distortion and even electric breakdown, which will lead to the insulation failure of the bushing.