Simulation Study Of Material Properties Influence On Electric Field Of Main Insulation On The Converter Transformer

In recent years,Chinese national economic growth is very rapid,the people’s living standards is increased significantly,the status of energy in the national life is more and more important,and electricity as secondary energy in all energy consumption occupies an extremely important position.Therefore,how to transport high-quality energy fast and reliable to the user has becoming the main consideration of the construction of transmission systems.The converter transformer plays a vital role in the high voltage direct current transmission system.It connects the DC side and the AC side of the grid so that the electrical energy can be transmitted to each other.However,the converter transformer is faulty happens sometimes because the very poor operation of the converter transformer.The converter transformer to withstand the role of different voltage types,the insulation structure of converter transformer is designed very complex and it is the weak link of converter transformer in the actual operation process.Therefore,it is necessary to study the electric field under the action of different voltage.Establishing the oil-paper insulation according to the RC equivalent circuit,establishing the upper part electric field simulation model of one ?400kV converter transformer valve side winding,simulating the valve side and the net side winding of the converter transformer when it withstand the role of DC,AC,polarity reversal voltage by using the finite element software ElecNet,and inferring the distribution of electric field and equipotential lines of the converter transformer under different voltage.Taking into account the temperature and nonlinearity of the insulating medium to the effect of the simulation results,the nonlinear change rule of conductivity of transformer oil and insulation cardboard is studied.The electric field of the converter transformer side winding is simulated when the polarity reversalvoltage is applied at different temperatures.The electric field strength of linear and nonlinear oil are increased with the temperature rise,while nonlinear oils can significantly reduce the maximum electric field strength present in the oil.According to the simulation results,finding out the weak link of the insulation.Optimizing the insulation by increasing the electrostatic plate thickness and the radius of curvature.Considering the anisotropy of the insulating medium,simulating of the electric field under the action of DC and polarity inversion voltage.The electric field of the converter transformer is simulated when the conductivity of the insulation cardboard is changed,under the action of DC voltage.It is concluded that the electric field of the insulating structure has little effect on the anisotropy of the paperboard.The electric field of the converter transformer is simulated by three kinds of an-isotropic nonlinear,an-isotropic nonlinear and an-isotropic nonlinearity under the effect of polarity inversion voltage.Without considering the nonlinearity of the insulating paperboard,the anisotropy of the insulating paperboard has little effect on the size of the electric field when the polarity inversion voltage is applied.The anisotropy of the insulating medium will weaken its nonlinear effect when considering the nonlinearity and anisotropy of the insulating medium.