| In recent years,the demand for electricity in various fields in our country has continued to increase,and the distribution of electricity demand has significant regional characteristics,and the demand in the eastern region far exceeds that in the western region.Therefore,UHV power transmission has become an important means of optimal allocation of energy resources.With the development of UHV,people are paying more attention to and worrying about the safety of electromagnetic exposure in the environment below UHV transmission lines.However,the current research on electromagnetic fields under transmission lines is dominated by single-circuit transmission.Due to the scarcity of land resources in the eastern and central regions of our country,the use of multiple circuits on the same tower has become an effective solution for saving line corridors and reducing project investment.Therefore,1000/500 kV four-circuit transmission on the same tower has become a development trend of UHV.Compared with the single-circuit transmission method on the same tower,the electromagnetic field distribution under the transmission line is more complicated.Therefore,it is necessary to evaluate the electromagnetic exposure in the environment of the 1000/500 kV four-circuit AC transmission line on the same tower.In this context,the thesis first modeled the actual 1000/500 kV four-circuit line on the same tower and its towers.The distributions of the magnetic field and electric field under the line under the 9 typical phase sequence arrangements are calculated and compared with the GB 8702-2014 and ICNIRP standards.Then,the influence of the magnetic field or electric field under the transmission line on the human body is studied separately,and the electric field intensity and magnetic induction intensity distribution in the body of a person standing under the line in different postures in the worst phase sequence condition are calculated.Compare these results with ICNIRP standards for electromagnetic exposure safety assessment.Finally,the electric field distribution in the body of the professional personnel wearing insulated shoes is calculated,and the relationship between the resistivity of the insulated shoes and the electric field strength in the body is analyzed.The results show that the change of the phase sequence arrangement will cause a large change in the magnetic field and electric field under the four-circuit line on the same tower.Compared with the different phase sequence arrangement,when the 1000 kV and 500 kV lines are arranged in a positive sequence and a symmetrical arrangement,respectively,The space magnetic field and electric field under the transmission line are the strongest,and the peak value of the magnetic induction intensity distribution curve at a height of 1.5m from the ground is lower than the standard limit of GB 8702-2014 and ICNIRP.When a person is located under a power transmission line,when analyzing the influence of the power frequency magnetic field generated by the high current of the transmission line on the human body,the magnetic flux density distribution in the body is basically the same as the magnetic flux density distribution in space.In the worst case,the electric field intensity distribution in the body in the hanging arm attitude is similar to that in the raised hand attitude,and the maximum value is much lower than the ICNIRP limit.The electric field in the body is vortex-like,and the electric field strength is strong in the legs,neck,shoulders,and outside of the body.After wearing insulated shoes,the electric field intensity in the legs and feet decreases,and the electric field intensity in the trunk and head does not change significantly.When studying the impact of the power frequency electric field generated by the high voltage of the transmission line on the human body,the electric field strength of the calf,neck and other parts is strong,and the electric field lines in the body are distributed from the head,shoulders,arms and other parts to the soles of the feet.In the worst case of phase sequence,the maximum internal electric field intensity in the hand-raised posture is greater than that in the vertical arm posture,the maximum internal electric field strength in the hand-raised posture is lower than the ICNIRP limit,and the electric field intensity in the head in the hand-raised posture is lower than that in the vertical arm posture.The intensity of the electric field in the head.After wearing insulated shoes,the electric field intensity in the foot decreases,but the electric field in the upper body of the human body does not change much.By comparing the calculated maximum magnetic flux density and electric field strength in the human body with the ICNIRP limit,it is shown that electromagnetic exposure under the1000/500 kV four-circuit AC transmission line on the same tower will not harm human health,but the danger of cumulative effects is not ruled out. |
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