Analysis Of Distribution Characteristics And Influencing Factors On Ion Flow Field Of HVDC Transmission Lines

With the developing of energy interne in China,the high voltage direct current(HVDC)project has faced new development opportunities and challenges.The problems of ion current field(including complex electric field and ion current density)caused by HVDC have caused more extensive attention.In order to analys the ion flow field distribution characteristics and the effects of lines structure and external environmental factors on ion flow field deeply,A two-dimensional numerical calculation model of the ion flow field of HVDC is developed based on the finite element method,which has certain reference significance for the early design and operation evaluation of the HVDC transmission lines.The main research work of this article is as follows:(1)Two-dimensional ion flow field calculation model is developed in COMSOL Multiphysics by coupling the "Transport of Diluted Species" and "Electrostatics" modules based on the existing numerical calculation model of the ion flow field of the direct current lines.In order to achieve efficient and accurate calculation results the following are considered during the modeling process:①Which had fine spatial resolution in the vicinity of conductors of the mesh and had gradually sparse away from the lines;②The direct solver is used to solve the stiffness matrix;③The optimized solver is used to modify the charge density on the surface of the conductors.And the calculation results in this paper are compared with the experimental results to verify the feasibility of the calculation model.(2)The ion flow field of HVDC line was mainly influenced by structures of the lines and external environmental factors.Firstly,the effects of lines structure,surface roughness on the ion flow field are investigated.It is shown that,the height has a greater influence on ion flow fields when compared with the pole spacing and intrabundle spacing.The increasing height of lines from the ground can effectively decrease the ion flow field.With the decrease of the surface roughness,the values of the electric fields and ion current densities increase slightly.Finally,the effects of the wind velocity on the distribution of space charge,the complex electric field and the ion current field density is analyzed.(3)By using the calculation model,the complex electric field of HVDC is calculated and analysed with a building nearby.Firstly,the complex electric field of the experimental model near the DC line was calculated,and the calculating resultes was benchmarked with the experimental results.Then the characteristics of the electric field distribution and space charge was calculated and analyzed when the HVDC transmission line is close to the building.Then the influence of the structural parameters of the building and wind speed on the complex electric field distribution of the HVDC transmission line which near the building was calculated and analysed.