| HVDC transmission technology has become the development trend of China's power transmission project in recent years due to its large transmission capacity,long transmission distance and so on.But because of the corona effect,the surrounding electromagnetic environment of HVDC transmission line is very complex,it increases the difficulty of live operation,and even threaten the life safety of the operators and the stable operation of the line.Because of the complex channel condition,the typical tower structure,polar distribution of polar line and the typical and changeable operation mode,the electromagnetic environment of double circuit HVDC transmission lines on the same tower is more complex,at the same time,the probability of outage of two circuit is very low,all these factors have brought more technical problems in live operation.Therefore,it is of great significance for the safe operation and maintenance of UHV DC transmission lines to study the electric field around the double circuit HVDC transmission lines on the same tower,and to evaluate the electric field on the surface.In this paper,based on the control equations of the combined electric field of double circuit HVDC transmission system,the finite element method(FEM)is used to solve the complex electric field of double circuit HVDC transmission lines on the same tower.At the same time,based on the above method and combined with actual live working of double circuit HVDC transmission lines on the same tower,a simplified model of the live working condition of double circuit HVDC transmission lines on the same tower is established,the distribution of electric field on the body surface of the double circuit HVDC transmission lines on the same tower is studied.The main work is as follows:First of all,all kinds of live working methods and related inspection and repair techniques of the±500kV double circuit transmission lines on the same tower are sorted and introduced.Then the main factors affecting the safety of live working personnel are combed and summarized;the principle and calculation steps of the finite element method are studied,the electromagnetic field equations and boundary conditions of the double circuit HVDC transmission lines on the same tower are analyzed,the governing equations for solving the composite electric field and the corresponding assumptions and conditions for the solution are determined.Secondly,according to the actual situation of the ±500kV double circuit transmission lines on the same tower and the simulation environment of COMSOL,the simplified transmission line model is established,the potential,charge density and electric field are calculated,the distribution of them in space and ground are studied,and the variation of electric field and ion current density at different altitudes is discussed.Finally,on the basis of the research on the multi line live operation method and the related maintenance technology of the ±500kV double circuit transmission lines on the same tower,in order to simulate the actual live working condition more comprehensive,in this paper,the modeling and simulation of the electromagnetic environment of the typical tower and the typical live operation under different operating modes are carried out.The distribution law of electric field is summarized.The safety suggestions for the actual safety protection and maintenance mode selection of live working of ±500kV double circuit transmission lines on the same tower are given out.It can be used as reference for the safety protection of live line operation in the ±500kV double circuit transmission lines on the same tower. |
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