Modeling And Calculation Of Ion Flow Field Considering Dielectric Characteristics

In recent years,the development of ultra-high voltage direct current transmission in China has been rapid.The total length of overhead direct current transmission lines in operation has been increasing year by year,and the objects crossed by the lines have become more complex and diverse.This makes the modeling and calculation of ion flow field problems in ultra-high voltage direct current transmission lines more complex.Therefore,it is necessary to improve the existing ion flow field calculation models based on the electrical characteristics of different material objects under the lines,Improve the accuracy of ion flow field prediction for ultra-high voltage direct current transmission lines.This article systematically studies the calculation method of ion flow field in axisymmetric and three-dimensional fields containing multiple media,providing ideas for solving ion flow field problems in ultra-high voltage direct current transmission lines in complex environments.Firstly,this article proposes a computational method for multi medium ion flow field problems applicable to two-dimensional axisymmetric models.The main work includes:deriving a general finite element formula for Poisson’s equation when the field contains multiple media and the surface area of the media accumulates surface charges;A storage method for element and node files suitable for solving multi medium ion flow fields using upflow finite element method was provided;The complementary variational method was used to solve the field strength in different dielectric regions;Explained the detailed calculation process of the calculation method;The effectiveness of the calculation method was verified through experiments.Secondly,this article proposes a solution method for the three-dimensional ion flow field in multi media based on the calculation method of multi media axisymmetric ion flow field.The main work includes:providing the finite element matrix equation for solving Poisson’s equation in a three-dimensional multi medium ion flow field and the calculation formula for solving the current continuity equation;The addressing method of node field strength and node charge density in solving current continuity equation by upflow finite element method is explained;The effectiveness of the calculation model was verified through experiments.Finally,based on the multi medium three-dimensional ion flow field calculation method proposed in this article,the characteristics of ion flow field around the insulating medium and the influence of electrical parameters of the medium on the ion flow field were calculated and analyzed.Compare the changes in ground field strength with and without insulating media and metal media;Analyzed the distribution characteristics of field strength on different sides of rectangular insulation medium;Analyzed the effects of different electrical parameters on the field strength around the insulating medium,the ability of the insulating medium to accumulate free charges,and charge polarity.