Sub-Model Method for Ion Flow Electric Field Analysis Including Complex Buildings Adjacent to UHVDC Transmission Lines

Corona discharge on high-voltage direct current (HVDC) transmission lines generates space charges that affect the ion flow electric field on the buildings nearby. According to China's national standards, the electric field on building platforms must be controlled under the limit. Due to the variety of buildings near HVDC lines, extensive calculations are needed to obtain the distribution of the electric field. A sub-model method for the upstream finite element method is proposed to improve the calculation efficiency of the 3-D ion flow electric field by setting a reasonable cut-boundary condition, which is obtained by calculating the complete model without buildings. By analytic derivation, the potential and charge density errors at the cut-boundary are proved to have nearly linear influence on the electric field calculation results. Then the setting principle of the cut-boundary is determined by analysing various calculation results. The sub-model method was found to be over 14.7 times faster than the complete model after calculating 432 models, and the results are in good agreement with the complete model. Finally, the enhancing and weakening characteristics of the electric field on one-layer and two-layer building platforms near HVDC lines are obtained. The research results are helpful for the design of HVDC projects with buildings nearby.