| With the enhancement of public awareness of ecological and environmental protection,people pay more and more attention to the health problems caused by electromagnetic field radiation in power transmission and transformation projects.Considering that strong electromagnetic field may allect human health,it is necessary to simulate the ground field strength of transmission lines in order to liminate unnecessary concerns.At present,there are some research results on electromagnetic field pollution caused by transmission and transformation lines at home and abroad,but there are still some factors that have not been considered:the calculation of power frequency electromagnetic field intensity around transmission lines is basically based on two-dimensional model,which often fails to accurately describe the temporal and spatial distribution of electromagnetic field intensity near transmission and transformation lines at 1.5m height from the surface.In addition.there are f'ew studies on the influence of meteorological factors and line sag on the electromagnetic field strength of transmission lines.In order to improve the calculation accuracy of electromagnetic field intensity near transmission and transformation lines,the key factors to change the electromaunetic field intensity environment of transmission and transformation lines are analyzed and the electromagnetic environment of UHV transmission and transformation lines considering meteorological factors is specially studied.(1)Using Ansoft Maxwell finite element electromagnetic field simulation soltware.two-dimensional model and three-dimensional model of transmission line considering sag are built respectively.In this paper,the results of two-dimensional model and three-dimensional model are verified and compared.It is found that the three-dimensional model can simulate the distribution characteristics of electric field near the transmission line more accurately than the two-dimensional model.Based on the results of the analytical method,it is found that the deviation between the maximum electric field strength obtained by the three-dimensional model simulation and the results obtained by the analytical method is between(+3%),which verifies the accuracy of the three-dimensional model.(2)The basic parameters of transmission and transformation lines are set up by Ansoft Maxwell finite element electromagnetic analysis software.Then,according to the division of typical meteorological areas,the range of meteorological changes(temperature,wind speed and icing)in different regions under extreme severe weather is clarified.Taking 500 kV UHV transmission and transformation lines as an example,the temperature changes,ice thickness changes,wind speed changes and icing with wind are simulated and analyzed.The influence of temperature and wind on the distribution of electromagnetic field intensity at 1.5m height near the transmission line considering sag is discussed.(3)The influence of shielded conductors on reducing the electric field intensity at 1.5 m above the ground near the UHV transmission and transformation lines is discussed.The shielding effect of the maximum electric field intensity at 1.5 m above the ground near the transmission and transformation lines considering sag is simulated and analyzed by using the electromagnetic field model of transmission and transformation lines.It is proved that the maximum electric field intensity near UHV transmission and transformation lines can be effectively reduced by the appropriate number(two shielding lines)and location(arrangement width d=7.2m.arrangement height h=2m)(56.70%without mitigation measures).This paper studies the temporal and spatial distribution of electromagnetic field intensity on the ground of UHV transmission lines under the influence of meteorological factors,and discusses the effect of optimizing the number,height and width of shielded conductors on the electromagnetic field intensity of shielded transmission lines.It is hoped that this paper can provide design reference for UHV transmission and distribution projects,and eliminate people's unnecessary worries and panic about UHV transmission lines. |
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