Research On The Electromagnetic Environment Of Transmission Line On The Same Tower

Multi-circuit transmission line on the same tower can fully utilize line corridor and reduce line construction cost. That is a good way of new electricity power transmission. But electromagnetic environment of quadruple-circuit transmission lines is one of the key problems that restrict the design, construction and operation. Therefore, the research on electromagnetic environment has important guiding significance.The electromagnetic environment of several kinds of typical quadruple-circuit transmission lines on the same tower is analyzed with CDEGS, including 110kV, 220kV, 500kV, 220/110kV and 500/220kV lines. The power frequency electric field, the line corridor, power frequency magnetic field, radio interference (RI) and audible noise (AN) is calculated; and the effects of tower type, the arrangement of conductors, the height of transmission lines, the additional shield wires, the spacing of split conductors, the diameter of the sub conductors and the altitude are discussed in detail, and the measures to improve the electromagnetic environment are proposed.There are 6~4 phase sequence arrangements for quadruple-circuit transmission lines on the same tower theoretically. In order to obtain the optimal arrangement, the electromagnetic environmental factors of transmission line are analyzed including power frequency electric field, the line corridor, power frequency magnetic field, radio interference and audible noise. By taking electromagnetic environment factors into account, the optimal phase arrangement for quadruple-circuit transmission lines on the same tower is obtained.The secure distance recommended by existing regulations cannot satisfy requirements of quadruple-circuit transmission lines cross the buildings. To calculate the secure distance of quadruple-circuit transmission line on the same tower passing over buildings, power-frequency electric field distortion on the roof and the balcony is calculated and analyzed. Effects on distorted electric field near the building of many factors are analysed systematically, such as the building's structure( including its height and area, radius and density of steel bars),the tower's height and conductors' arrangement on the tower.The results show that the distortion of the electric field near the building is a key factor to decide secure distance between buildings and lines which relates to the line voltage levels, building height, tower structure and other factors. And the secure distance between conductors and building is proposed based on distorted electric field, including minimum vertical secure distance and minimum horizontal secure distance.