Calculation and Analysis of Surface Electric Field Intensity of Key Part in DC Power Transmission System

Calculation of surface electric field of key part of the DC power transmission system is important for prevention of surface discharge of the converter valve tower and control of surface field intensity; the field intensity calculation results were proposed under different schemes and the optimized positions and the structural parameters of the grading ring were validated in this article by analyzing calculation of the surface field intensity of the key part of the idealized DC power transmission converter system model by boundary element method in numerical calculation of electromagnetic field.By calculating the surface field intensity of the valve box structure without grading ring and the surface field intensity of the whole structure to which the grading ring was applied respectively and analyzing the effects of the position and the distance between grading rings to the surface Electric Field Intensity of the valve structure specifically, wherein the comparison was implemented as well to explain that the greater the distance among the external grading rings of the converter valve structure was, the greater the field intensity at the middle point on the edge corresponding to the valve box structure would be; and the surface field intensity of the corner part corresponding to the valve box model was reduced significantly as a result of application of the grading ring. That whether the parameters, such as the dimensions of the grading ring, the distance, etc. after being changed meet the requirement of shielding were studied thoroughly by calculating the surface field intensity of key part of the converter valve in the actual power transmission project, the calculating models of the valve module and the column structure of the transverse plate were proposed to take into account after adjusting the structure of the shielding system; the surface field of the key part in the valve tower structure was analyzed in accordance with the method of applying the voltage; the inexistence of corona phenomenon was validated and the laws were summarized; and the insulating feasibility of the shielding system in the practical project was verified. Moreover, the reference basis could be provided for designing and planning of the grading ring of the DC power transmission converter valve in the design scheme in the article.