Research Status and Prospect of Space Charge Measurement Technology in Gas Medium under DC Voltage

High voltage direct current(HVDC) transmission has the advantages of large capacity, low loss and small footprint, which is an important support for solving the problems of high-density and narrow channel transmission in large cities and promoting the national strategy of "carbon peak and carbon neutrality". But high-voltage direct current transmission lines with strong corona discharge caused by the space charge effect(the electric field distortion and the ion flow field) complicated electromagnetic environment around the high-voltage direct current transmission lines, so the space charge distribution in DC transmission line characteristics and measuring method of study for guiding the engineering design of DC transmission line is of great significance. The formation mechanism of space charge is firstly described, as well as the similarities and differences of its distribution under AC and DC lines. The influence of transmission line structure and external environment conditions on the density distribution characteristics of space charge and the main influencing factors are analyzed. In addition, the research progress on the experimental measurement methods of space charge distribution in gas media at home and abroad is summarized, and the correlation, advantages and disadvantages of different measurement methods are analyzed. On this basis, the urgent problems in the space charge measurement research are proposed, such as the three-dimensional measurement method of space charge still needs to be improved and further studied, and the future prospects of space charge in the study of corona discharge mechanism are prospected.