Calculation Of Hybrid Electric Field Of AC/DC Transmissionlines Erected In Acommon Corridor

In the face of increasingly scarce land resources and the grim reality of new transmission corridors are difficult to obtain,our country put forward to solving approach of DC and AC transmission lines being erected in a common corridor.At the same time,with the large-scale construction of large capacity andhigh voltage level transmission project and people's enhanced consciousness of environmental protection,the electromagnetic environment problems caused by the transmission line are more and more valued by the public.Therefore,a systematic study ofelectromagnetic environment of parallel AC and DC transmission lineshas a importantly theoretical and practical significance.The parameters to measure electromagnetic environment of transmission lines include: electric field effect,the magnetic field effect,audible noise and so on.This paper mainly studies the electric field effect of parallel AC / DC transmission lines.DC and AC electric field finite element calculation model are built based on the COMSOL,what's more,calculation and analysis of the DC circuit and the AC line electric field distribution are accomplished.On this basis,the superposition model and analytical model for calculating the hybrid electric field are studied,then the superposition model is used to solve the hybrid electric field in the same corridor of the 800 kV UHVDC lines and 500 kV EHV lines,and the calculation results of the model are in good agreement with the test results.The distribution of hybrid electric field is affected by many factors,the effects to the hybrid electric field from the height of conductor to the ground,approaching distance,inter-phase distance,phase sequence arrangementand sub conductor radius are mainly discussed.The following conclusions are obtained.The change of the height to the ground of AC lines will directly result in the change of AC component while the hybrid electric field will not be affected.However,the DC component andhybrid electric field will change significantly with the change of the height to the ground ofDC lines,therefore,it is necessary to determine a reasonable height of AC / DC lines to the ground.The change of distance between AC and DC lines doesn't affect the maximum value of AC / DC component and hybrid field strength,but when the distance between the two increases,the coverage area of the high field strength increases obviously and there's an optimized approaching distance between the two.The AC component and high electric field coverage area will be significantly reduced when the AC lines inter-phase distance decreases,but the reduction of the DC linesinter-phase distancedoesn't affect the DC component and hybrid electric field distribution.The AC componenthas the maximum when the AC lines in accordance with the positive sequence,while minimum AC component of reverse order.The sub conductor radius has no effect on the AC / DC component and the hybrid electric field distribution.