| In recent years,the State Grid Corporation has carried out a large number of related plans for UHV construction.Because it can save the width of the corridor and improve the transmission capacity and stability,the double-circuit transmission line has also become an indispensable part of UHV construction.This paper conducts a safety assessment of the electromagnetic environment of a double-circuit transmission line that few people have studied.Through quantitative research on the electromagnetic environment parameters,the public can have an intuitive understanding of the electromagnetic environment of the double-circuit transmission line,reducing the public's concerns about the electromagnetic environment safety of the double-circuit transmission line,which is conducive to China's construction of the double-circuit transmission line.Secondly,through the study of this paper,considering the electromagnetic environment,the selection of related parameters for UHV double-circuit transmission line is also of certain reference significance.In this paper,the finite element software COMSOL is used to calculate the magnetic induction and induced electric field strength values directly under the wire under different parameters.Next,the effects of power-frequency magnetic fields and power-frequency electric fields on the human body of double-circuit UHV AC transmission lines were simulated and compared with the exposure guidelines for safety assessments developed by the International Commission on Non-Ionizing Radiation Protection(ICNIRP).For the electric field effect,the differences in the electric field distribution and size of the human body in different postures are also compared.Finally,in order to verify the accuracy of the simulation results,field experimental measurements were carried out under certain UHV double-circuit transmission lines.The results show that:for power frequency electric field,the voltage level,minimum height to ground,phase sequence,number of conductor splits and phase spacing all affect the electric field strength under the double-circuit lines,among which the voltage level,the effect of minimum height to ground and phase sequence are more obvious.For the power frequency magnetic field,the load current,the minimum height to ground,phase sequence,phase spacing and number of conductor splits all affect the magnitude of magnetic induction,while effect of the minimum height to ground and phase sequence have a significant effect.Regardless of whether it is an umbrella-shaped tower or a drum-shaped tower,under the power frequency magnetic field environment,the magnetic induction intensity,the induced electric field intensity,and the induced current density are all far less than the safe limit of ICNIRP.The maximum values of the them under the umbrella-shaped tower are 3.33?T,0.417mV/m and 0.042mA/m~2 respectively,they are 1.6%,0.1%,2.1%of the safety limits;The maximum values of them under the drum-shaped tower are 4.23?T,1.54mV/m,and0.154mA/m~2,respectively,they are 2.1%,0.4%,7.7%of the safety limits.In the power frequency electric field environment,the induced electric field strength values of the umbrella-shaped tower and the drum-shaped tower are smaller than the safety limits specified by ICNIRP,the maximum values are 97.9mV/m,100mV/m.They are 24.4%and 25%of the safety limits,respectively.Larger values of induced current density are located in the lower legs and feet of the human body.This suggests that ordinary people and related professionals should take certain measures to protect their feet and calves.The different postures of the human body will also affect the distribution of the electric field in the human body,and the specific changes are related to the shape of the human body.The research in this paper shows that the electromagnetic environment of UHV double-circuit AC transmission lines will not pose a threat to human health. |
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