In order to evaluate the electromagnetic environment of the 750 kV four-circuit transmission lines accurately, and design the optimal tower type and phase sequence of the four-circuit lines, the finite element method is used to analyze the distribution characteristics of power frequency electromagnetic field under the line. The excitation function method and the empirical formula method are used to calculate the radio interference and audible noise distribution under the line respectively. Electromagnetic environment parameters of various phase sequences of two tower types are analyzed to determine the optimal phase sequence of 750 kV four-circuit transmission lines. The results show that the electromagnetic environment of transmission lines is strongly influenced by different tower types and phase sequences. The magnetic flux density and radio interference of the various phase sequences of the two tower types reach the limit of code, and 43.52% and 64.81% phase sequences reach the audible noise limit conditions respectively. Electric field intensity is a main influence factor of electromagnetic environment. The optimal phase sequence layouts of the two tower types are 1661 and 1522, and the electric field intensities are 9.66 kV/m and 9.12 kV/m. The calculation method and results can be used for reference in practical engineering.
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