Calculation And Analysis Of Electric Field In Line Winding Side,Valve Winding Side Of Converter Transformer

Converter transformer is important equipment in HVDC. The working reliability of converter transformer has an important effect to HVDC. In respect of insulation design, the difference from ordinary transformer is that converter transformer is under the mixed effects of AC, DC voltage and polarity reversal voltage. It makes the insulation design of converter transformer is more complicated. So, the insulation design of converter transformer is worth further studying.Electric field model of±500kV converter transformer is established by finite element software ANSYS. AC field in line side winding end, AC field, DC field and polarity reversal field in valve side winding end of converter transformer are calculated. Distribution rules of electric field under the effect of different excitation are obtained, and the maximum electric field values are calculated, the weak areas of insulation in converter transformer are found. Through the calculation of polarity reversal field with different resistivity ratio and resistivity absolute figure, the effects of insulation medium resistivity to polarity reversal field is studied.Nonlinear, anisotropy DC field calculated program is compiled by APDL of finite element software. In the program, the factors that insulation resistivity changes with the electric field and the anisotropy of insulating board are considered. Nonlinear, anisotropy DC field in valve side winding end of converter transformer is calculated. The changing of nonlinear, anisotropy DC field with respect to linear electric field is obtained.Two dimension model of bushing lead-out wire in valve side winding of converter transformer is modeled by finite element software, and electric field of bushing lead-out wire under different voltages are calculated and analyzed. The electric field distribution of bushing lead-out wire under different voltages is obtained. The conclusions obtained in this thesis have significant engineering value to study the electric field and insulation structure of converter transformer.