| With the progress of science and technology,the load of electricity in China has increased greatly,and the current 500 kV power grid structure has been difficult to meet the demand for electricity required by economic development.On the other hand,the distribution of energy and electricity load is not uniform.Most of the energy is concentrated in the north and the west,and according to different regions,the energy structure and regional load characteristics are significantly different,which determines that China needs to build a long-distance,highcapacity 1000 kV ultra-high voltage transmission and transformation system.With the development of 1000 kV UHV transmission technology,resources of the line corridor are limited,and UHV will inevitably cross the building area,although many scholars at home and abroad have studied the power frequency electromagnetic field under the UHV ac transmission line.However,according to the practical problems after the operation of UHV ac transmission lines in recent years,there is no relevant literature to study the problem of induced electricity in the buildings with a large number of steel frame structures(greenhouses dense areas,metal pipes,iron sheet buildings,etc.)under the lines.It is of great significance for the design and construction of power lines to analyze the problem of induced electric over-limit in offline buildings,and study the method of induced electric quantization budget estimation,which can do a good job for the scientific and reasonable determination of the corridor width.The main research contents and conclusions of this paper are as follows:(1)Study on theoretical calculation of power frequency electromagnetic field under transmission line.This paper starts with the numerical calculation method of power frequency electromagnetic field around the transmission line,compares and analyzes the advantages and disadvantages of these methods,introduces the infinite element idea on the basis of threedimensional finite element,and establishes the simulation model of different voltage levels with ANSYS simulation software.Through comparative analysis,it is shown that the simulation method of finite element and infinite element combination can improve the efficiency and accuracy of simulation calculation,and the established model can be used for subsequent simulation calculation of inductive electricity.(2)Study on the simulation of induced voltage and induced current density based on ANSYS.According to the method of finite-infinite element combination,the simulation calculation model of different wire erection height,running current level of different lines and spatial position parameters of different steel frame structure is established.The conductor phase sequence of transmission line is arranged in reverse sequence.The influence degree of each parameter on the induced voltage and induced current density on the steel frame is analyzed by using the simulated cloud image.The influence law is studied through data comparison.It is of great significance to the design of transmission line.(3)Research on induction electric quantization estimation method and design of auxiliary calculation software.The emphasis of this paper is to propose a method of quantifying the induced voltage and induced current density of steel frame structure under UHV line by summarizing and analyzing the simulation data.In the design process of UHV line,it provides theoretical reference for the workers,reduces or avoids the accidents caused by induced electricity after the line is built and put into operation,and guarantees the public safety.Combining the induction electric quantization estimation method with the electrical parameter calculation method,an auxiliary computing system was developed by using matlab graphical user interface,which greatly improved the efficiency and accuracy of line design.Finally,three measuring points of metal pipeline under UHV ac line are selected,and the values calculated by the software are compared with the measured values to verify the accuracy of the quantitative estimation method and the software in this paper.The finite element-infinite element simulation method combined with the mesh refinement technique can save more than 45% of the simulation time,and the accuracy is higher.Electromagnetic induced voltage and induced current are closely related to the three parameters discussed in this paper.The operating current level of transmission line has the most obvious influence on the induced voltage and induced current.The influence of line erection height on induced voltage and induced current varies with the distance between the steel frame and the line axis.The effect of limited line elevation on induced electricity is less than that of the other two parameters.Considering the factors such as line erection cost and transmission efficiency,the construction standard of steel frame building under UHV is given.The proposed method of quantifying the estimated induced voltage and induced current density is in line with the requirements of engineering calculation. |
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