High voltage direct current equipment and transmission lines are highly susceptible to atmospheric environment-induced conditions, which have considerable influence on their ion current, space charge, and ground-level electric field patterns. Therefore, it is imperative to thoroughly understand the influencing factors of ion current environment for effective electric power design and planning. This requires the understanding of the physical mechanism of ion flow fields of monopolar and bipolar lines. To date, considerable research, mainly based on computational theory of ion flow, have been conducted to provide more insights on the factors influencing the ion current environment of direct current transmission lines. Nevertheless, very few studies have attempted to elucidate the effects of aerosol climate on ion current environment despite their potential effects on the environment.
To this note, a team of Tsinghua University researchers: Yong Yi, Zhengying Chen, Wenxi Tang, and Professor Liming Wang studied the ion flow environment of direct current transmission lines in the presence of charged aerosol particulates using the upwind-finite element method. Specifically, the researchers calculated the ion flow environment based on appropriate assumptions. Their research work is currently published in the journal, Electric Power Systems Research.
In their approach, the current equation continuity problem was solved by the upwind-finite difference method, while the finite element method was used to solve the passion equation with the large-scale sparse matrix solution acceleration technique. Consequently, Fuchs theory coupled with the Stokes-Einstein relation, was used to determine the ion-aerosol attachment, electrical mobility, and diffusion coefficients of the charged aerosol in monopolar and bipolar ion flow environments. The proposed method was finally used to calculate monopolar and bipolar direct current lines to verify its practicability.
The authors reported that the proposed method could be used to calculate the ion flow environment of both monopolar and bipolar high voltage direct transmission lines (± 350 kV to ± 750 kV) under different aerosol densities. Moreover, the aerosol exhibited a significant influence on the spatial distributions of the charge density. For instance, the significant increase in the ground-level electric field in the down-wind direction was attributed to the effects of the dominant charged aerosol particles. Also, the tendency in the ground-level electric field in the presence of aerosol was observed to be the same as that in the absence of aerosol.
In a nutshell, the study proposed the use of the upwind-finite element method to determine the ion flow environment of direct current transmission lines in the presence of charged aerosol particulates. The computational results based on appropriate assumptions together with the experimental validations approved the effectiveness of the proposed technique in studying the effects of the aerosol on the ion current environment of practical monopolar and bipolar direct current transmission lines. In a statement to Advances in Engineering, the authors stated that findings advance our knowledge on the physical mechanisms of the effects of the aerosol for the betterment of future research on the aerosol climate effects on the lateral profile of the ground-level electric field and ion current density of direct current transmission lines.
Yi, Y., Chen, Z., Tang, W., & Wang, L. (2020). Calculation of ion flow environment of DC transmission lines in the presence of charged aerosol particulates based on upwind-FEM. Electric Power Systems Research, 184, 106289.