Converter Transformer Winding End Electric Field Analysis And Optimization

High voltage direct current transmission because of its low cost and small circuit loss, system stability, suitable for long-distance and large-capacity power delivery and easy realization of non synchronous power grid interconnection and other advantages, which in our country has been rapid development. As an important equipment in HVDC, the working reliability of convert transformer has an important effect to HVDC. Compared to AC transmission power transformer, converter transformer not only to be under AC voltage effect, also under DC voltage and polarity reversal voltage effect. In the DC voltage and polarity reversal voltage under the action of electric field distribution in converter transformer is different from the common power transformer. Therefore, whether it is from the high voltage direct current transmission trend of rapid development and its insulating structure complexity and particularity of working condition, worth further research and study.In this thesis, a±500kV converter transformer winding end insulating structure is analyzed and calculated. Includes a DC electric field, polarity reversal electric field and angle ring radius optimization.In the calculation of DC electric field, introduced the method of calculate the nonlinear anisotropic DC electric field. Considering the electric field strength and temperature impact on conductivity and the paperboard laminate orthotropic anisotropic.In the calculation of polarity reversal electric field, analysis of model structure and material properties on the long time DC electric field effects, as well as the material properties and the length of time to reverse polarity reversal electric field effect. Finally, calculated of isotropic polarity reversal electric field and orthogonal anisotropic polarity reversal electric field.In the calculation of three-dimensional electric field, introduces the modeling and mesh generation technique. Calculated three-dimensional AC electric field, DC electric field and polarity reversal electric field and compared the calculate results with the two-dimensional field.The angle ring radius optimization, introduces the parametric modeling method and finite element method and optimization algorithm combining method. Finally, analysis the insulation margin of the optimized results.