| Ultra-high Voltage(UHV)power grid has the advantages of long transmission distance,low loss,large transmission capacity,saving line corridor width,etc.It is the only way to solve the problem of reverse distribution of energy resources and power load in China.With the improvement of voltage ratings,the influence of power frequency electromagnetic field produced by transmission lines and substations on human body is attracting more and more attention.Based on different human body models in domestic and foreign research,many valuable research results have been obtained by estimating,mathematically solving Maxwell equation,numerical calculation,etc.However,the conductor arrangement and voltage ratings in foreign research are different from those in China,the domestic application of those research findings is limited.And the research on the exposure level of UHV transmission and transformation environment to human power frequency electric field is still blank.In this thesis,the human body has been taken as the research object,and the distribution of induced current density produced by power frequency electric field in UHV transmission and transformation system has been deeply studied.The following studies have been carried out:1)The three-dimensional finite element analysis software ANSYS has been used to establish the human body model with different arm postures.The electrical characteristics parameters of the human body model have been investigated.The electrical characteristics parameters of the human body model in this paper are determined according to the research results of other scholars.The effects of power frequency magnetic field and skin-collecting effect on human body have been analyzed.2)According to the drawings provided by the design institute,the calculation models of UHV transmission lines and substation are established respectively.The distribution of power frequency electric field under UHV AC transmission lines and inside substations is simulated and analyzed.The distribution of electric fields under UHV AC transmission lines and inside substations are obtained.The positions with maximum electric field strength have been determined.3)The human body model has been set at those positions with maximum electric field strength.The electric field intensity and current density distribution inside and around the human body under the transmission line and in the substation are simulated and calculated.The effects of human body on the electric field distribution under the transmission line and in the substation are compared and analyzed.The human body's shoes and arm posture on the human body and its surroundings are studied.The influence of electric field intensity and current density distribution on human body is calculated.The resistance and capacitance of human body to the ground are calculated.The electric field intensity and current density distribution in human body under transmission line and in power station has been obtained.According to the relevant restriction standards,the safe area under the transmission line and in the substation has been proposed based on the induced current density of power frequency electric field.The research results of this paper can be used to determine whether the power frequency electric fieldof the existing UHV transmission and transformation system is safe for human body.It will also have a certain reference value for the preliminary design of the follow-up UHV projects. |
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