Study On The Ion Flow Field And Nearby Insulators In HVDC Transmission Lines

With the rapid development of HVDC transmission project in China,the domestic 500 kV ultra high voltage direct current(HVDC)transmission technology has been widely used,and the 800 kV UHVDC transmission line has been put into operation.The insulation problem is a critical problem of the HVDC transmission.The ion flow of HVDC that emerge space charge has influence on the flashover of the insulator,so the design of insulator on DC transmission line need to be considered.The numerical calculation method of ion flow field of the DC transmission line is studied in this paper,the upstream finite element method which used to solve the ion flow field of DC transmission line is discussed,At the same time,the influence of space charge distribution of ion flow field in DC transmission on the operating parameters of insulator is analyzed under certain conditions.In this paper,firstly,through the analysis of ion flow field theory,the mathematical equations and boundary conditions are derived,and the upstream finite element method is used to solve the convergence problem in the iterative process,which make the iterative process completed faster;Then,finite element method is used to solve the mathematical model;Finally,a program based on MATLAB is achieved which is confirmed the validity of the calculation by comparing the analytical solutions of cylindrical structure with the function of getting ground electric field strength and ion flow density of DC transmission line.The influence of wind speed,height of wire,wire voltage on the ion flow field is analyzed,which results show that the height of wire near the ground ion flow is large,the wire voltage level has a certain impact on the ion flow field;also the space charge on the surface of the insulator and the voltage distribution is also affected.The research results of this paper can provide the basis for the electromagnetic environment evaluation of HVDC transmission project.Further more,it can provide guidance for the flashover of HVDC insulators under complex atmospheric conditions.