Insulation structure design of valve side bushing of ± 400 kV converter transformer

The design margin of valve side bushing of ± 400 kV converter transformer is lower than that of UHV converter transformer, and the number of valve side bushing used in ± 400 kV converter transformer is large in converter valve hall, so it is necessary to analyze and discuss the insulation structure design of valve side bushing of ± 400 kV converter transformer. The heating mechanism of the double conductive tube structure of the valve side bushing of ± 400 kV converter transformer is analyzed, the design size of the double conductive tube structure is given from the theoretical analysis point of view, the core insulation structure of the bushing is further optimized, the external insulation design scheme of the bushing is given from the perspective of internal and external insulation coordination, and the overall electric field distribution is calculated and checked. The radial electric field intensity is controlled at 3.11 kV/mm under wor-king voltage, and the axial electric field intensity is controlled at 0.51 kV/mm under the power frequency withstand voltage, which meet the requirements of electric field intensity control in the design of valve side bushing of ± 400 kV converter transformer. Furthermore, the type test of the developed valve side bushing of ± 400 kV converter transformer is carried out, and the results show that the developed bushing passes the typical type tests such as power frequency dry withstand voltage test with partial discharge measurement, lightning impulse dry withstand voltage test and temperature rise test. © 2021, Electric Power Automation Equipment Press. All right reserved.