Study On Electric Field And Radio Interference Of Parallel Transmission Lines By AC And DC

To adopt parallel AC-DC line has become an important consideration in design of the transmission lines for the sake of the shortage of the transmission corridors. With the increase of both voltage level and the transmission capacity, many electromagnetic environmental issues have become increasingly evident and have aroused widespread concern. Therefore, the electromagnetic environment around the transmission lines is of importance for the design, construction and operation of high voltage transmission lines. Due to these, it is necessary and significant to theoretically estimate and analysis the electromagnetic environment around high-voltage transmission lines.Electromagnetic environmental issues of transmission lines include electric field effects, radio interference, audible noise and so on. In this work, emphasis is on the study of electric fields and radio interference around parallel AC-DC lines. For the parallel lines by500kV AC line and±800kV DC line and with the use of the finite element method, the electric field distribution under the lines and the radio interference characteristics of the lines have been studied in this work. Especially, the influences of the several factors on both the electric field distribution and the radio interference characteristics have been systematically analyzed. These factors include the center spacing, the line height relative to ground, the bundle spacing, and sub-conductor radius. The following conclusions are obtained. As the center spacing increase, the hybrid electric field become smaller and the distribution range of the radio interference get larger, and thus an optimization of the center spacing should be made. There is an ignorable effect of the center spacing on the hybrid radio interference around the DC line. Both the hybrid electric field and hybrid radio interference can be reduced by increasing the line height, but the hybrid radio interference changes a little. And there are no evident bundle spacing dependence of the hybrid electric field and hybrid radio interference in the space range between AC line and DC line. Increasing the radius of sub-conductor has little effect on hybrid electric field, but can reduce the hybrid radio interference.Based on the calculation of the electrical field of parallel AC-DC line, the capacitances of the lines have been calculated, the influences of the several factors, i.e. the center spacing, the line height relative to ground, the bundle spacing, and sub-conductor radius, on the capacitance have been systematically analyzed, and the following conclusions are given. There is no evident dependence of center spacing and line height relative to ground on the capacitance of parallel AC-DC line. The capacitance can be reduced by increasing bundle spacing and can enlarge by increasing the radius of sub-conductor.