I. INTRODUCTION
In a direct current transmission project, lots of work has been done by scholars all over the world using different methods to calculate an ion flow field under the direct current transmission line. Ref. [1]used the analytical method proposed by M P Sarma et al. based on the Deutsch hypothesis that the resultant field strength formed by the combined action of the wire exterior charge and the spatial ion charge is in the same direction as the electric field strength formed by the wire exterior charge alone, and the assignment is different. The influence of structural parameters such as traverse radius on the exterior synthetic field strength and ion current density was first proposed by Canadian scholar Janischewch et al. in the late 70s of the 20th century [2], and has been improved since then [3], which abandons the Deutsch hypothesis and has high calculation accuracy. The upflow FEM proposed by Professor Takuma [4] is possible to be utilized to deal with an ion flow field considering wind speed, and method has been