| With the rapid development of China's economy, and rapid growth in electricity demand, high voltage Power Transmission Equipments has been greatly increased. Environmental problems caused by power frequency electromagnetic field which generated by a wide variety of high-voltage transmission and distribution equipments issue more and more attention; and their impact on nearby environment, their distribution, attenuation and how to protect are the main contents of this study.There are five overhead transmission lines with different voltage levels and one typical substation as representative in this paper, respectively, the power frequency electric and magnetic fields distributed under the transmission line and inside the substation is being studied, according to the electromagnetic environmental assessment standards of EMF protection of transmission equipment, some feasible suggestions are put forward on how to protect the radiation especially when the high-voltage overhead lines are across the houses and who work in the substations .EMF of over-head transmission lines are interrelated with span of lines, mode of transfers and parameter of circulation etc. From distribution and attenuation rules of PF-EMF, we bring out protective distant. The power frequency electric field (4.275kV/m) of the space between two or more lines was a bit bigger than the national commendatory standard. And then the calculated and simulated results were got by an improved charge equivalent method, which added the impact of equivalent charges form nearby power lines.In substations, there are many power frequency equipments and disposal modes. Form a large number of measured data; we can conclude that the EMF level is far below the limits.Compare these data with the radiation limits of national standards on public and occupational exposure, we can restrict protection distance. It can provide us the reference knowledge to protect healthy of public and occupational people.
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