| In recent years,China’s demand for electricity has been continuously increasing,and due to the uneven distribution of energy between the east and west of China,ultra-high voltage transmission has become an important way of resource allocation.With the continuous development of ultra-high voltage technology,the electromagnetic environment problems brought by ultra-high voltage transmission lines are gradually becoming prominent,and more and more people are paying attention to the safety issues of human beings under ultra-high voltage transmission lines.In this thesis,we use COMSOL finite element software to model the±800 k V UHV DC transmission line to obtain the distribution of ground nominal electric field,synthetic electric field and ion current density.The influence of line structure on nominal electric field,synthetic electric field and ion current density on the ground is calculated by taking conductor height,subconductor radius,split spacing and pole spacing as parameters.Based on the Chinese human body size standard,a three-dimensional human model for minors is constructed,and the safety of the electromagnetic field generated by ± 800 k V UHVDC transmission line during transmission to the minors is evaluated.The electric field effects of minors in nominal and synthetic electric fields,as well as the effects of different conductor heights and different standing positions on the electric field effects of minors are studied.At the same time,adult human models are established to compare the results with the limits set by the International Commission on Non-ionizing Radiation Protection(ICNIRP).The relevant research and results are as follows:(1)The influence of UHV DC transmission lines on minors was studied.When the transmission lines were close to residential areas,the height of the conductors was 21 m.In the nominal electric field,the electric field intensity of minors’ bodies was mainly distributed in the ankles,necks and underarms,and the maximum value of the electric field intensity appeared at the ankles and was 0.195 V/m,and the maximum value of the electric field intensity of brain tissue was 32.5 m V/m;In the synthetic electric field,the maximum value of the electric field strength was 0.360 V/m for minors’ bodies and 58.6 m V/m for brain tissue;the maximum value of the electric field strength for minors’ bodies was within the ICNIRP general population body limit of 0.4 V/m,and the maximum value of the electric field strength for brain tissue was also within the ICNIRP general population central nervous system limit of 0.1 V/m.By lowering the height of the wire to 18 m,the maximum value of the electric field intensity in the synthetic electric field was 0.412 V/m in the minor’s body and 72.8 m V/m in the brain tissue.The electric field intensity at the minor’s ankles was slightly greater than the ICNIRP general population limit at this point,but the electric field intensity in the brain tissue was still within the ICNIRP general population limit for the central nervous system.To change the standing position of minors,when the human body is in the center of the transmission line,the electric field intensity mainly distributes in the thorax,axillary,inner thigh and ankle.In the synthetic electric field,the maximum of the electric field intensity appears in the armpit,the maximum value is 0.049V/m,the maximum value of the electric field intensity of the brain tissue is 2.46 m V/m,and the electric field intensity of each part of the minor is far less than the limit of the general population of ICNIRP.(2)The influence of UHV DC transmission lines on adults is studied and the results are compared with those of minors.In a synthetic electric field,the maximum body electric field strength was 0.607 V/m for adults and 48.5 m V/m for brain tissue.In any electric field environment,the maximum body electric field strength of minors was less than that of adults,but the electric field strength of minors’ heads was slightly greater than that of adults,so that the exposure of minors’ heads is of greater concern.The exposure of minors under UHV DC transmission lines was obtained in this study.When the transmission lines were close to residential areas,the body electric field intensity and brain tissue electric field intensity of minors under the conductors were below the ICNIRP limits,indicating that electromagnetic exposure under ±800 k V UHV DC transmission lines does not cause significant damage to the human health status of minors. |
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