Effect Of Vegetation On Electromagnetic Environment Of 1000kV Ultra High Voltage AC Transmission Line

In recent years,the demand for electricity in various fields in China has been rising,but the energy-rich areas in China are inversely distributed with the load center areas,so ultra-high voltage(UHV)transmission has become an important method to optimize the allocation of energy resources.At the same time,the electromagnetic exposure of UHV transmission lines is drawing more and more attention and concern.The dense transmission lines compress human living space and affect the natural landscape and living environment seriously.It is a challenge of the future transmission of electric energy resources in China that how to minimize the impact of UHV transmission lines on the environment.At present,studies on the influence of electromagnetic environment on human biology in UHV transmission lines conclusions have been provided some reference value.However,there is still a gap in the study of electromagnetic exposure safety in the presence of vegetation in the transmission line corridor,so the effect of vegetation on the electromagnetic environment of UHV transmission lines is an important research content.In order to study the effect of vegetation on the electromagnetic environment of ultra-high voltage AC transmission lines,the models that according to the average height proportion of adults(standing posture)and the size of common vegetation(shrubs and high trees)in real life were established by the three-dimensional modeling software Solid Works.The fourth order Cole-Cole model and the principle of vegetation electrode were used to calculate the relative dielectric constant and conductivity of human body and vegetation at 50 Hz power frequency.The Mao Tou tower that was most typical and extensive used in the Jindongnan-Nanyang-Jingmen ultra-high voltage AC demonstration engineering,was selected as the research object for tower poles.And the equation of suspension chain line based on the overhead line of equal height of the suspension point makes it more suitable to the reality.The finite-element multi-physics simulation analysis software COMSOL Multiphysics was used to determine the safety assessment models for the effects of ultra-high voltage AC transmission lines on the human body’s industrial frequency magnetic field and industrial frequency electric field in three conditions:without vegetation,with shrubs and with high trees,respectively.The magnitude and distribution of the magnetic induction intensity,induced electric field intensity and induced current density around the human body,on the skin,in the trunk and in the central nervous system in each model were calculated in sequence.Finally,the calculation results under the three conditions were compared with the electromagnetic exposure safety threshold established by the ICNIRP guidelines.In this thesis,the maximum values of the magnetic induction intensity of the human body in the three environments of non-vegetation,presence of shrubs and presence of tall trees are12.823μT,12.724μT and 12.711μT,which were nearly the same.The maximum values of the induced electric field strength and induced current density inside the human body in the presence of vegetation in the power frequency magnetic field effect were 0.475 m V/m and0.157 m A/m~2,respectively,which were 48.3%and 52.3%of those in the non-vegetated environment.The maximum values of the induced electric field intensity and induced current density inside the human body in the presence of vegetation in the power frequency electric field effect are 1.38 m V/m and 0.490 m A/m~2,respectively,which are 67.9%and 55.6%of those in the non-vegetated environment.None of the results of the simulation calculations exceeded the safety threshold of ICNIRP,and the line with the presence of vegetation was superior to the line without the presence of vegetation in terms of electromagnetic exposure dosimetry and security risks.This study provides accurate measurements of human electromagnetic exposure in different terrain environments and reduces the apprehension and panic of residents near the transmission lines.The results of this paper can provide the necessary reference for the development of electromagnetic exposure safety standards in China.