Calculation and Analysis of Audible Noise of Transmission Lines in the Crossing Area

With the rapid development of UHV transmission technology, the continuous improvement of voltage level has caused the deterioration of the electromagnetic environment, especially the audible noise. Therefore, in order to optimize the design of the UHV transmission line for early planning and economic investment, it is necessary to predict and analyze the audible noise of the transmission line to provide audible noise limitation basis for the erection of the transmission line. At present, the calculation of audible noise of transmission lines, which apply to single transmission line, mainly treat the wires as infinite and straight. This is based on the 2-D calculation method. However, the calculation of audible noise across cross-over areas requires the establishment of a 3-D model. There are few researches on the calculation of audible noise based on 3-D model. The calculation of the audible noise at a certain point in 3-D space is based on the principle of superposition. We consider a limited-length transmission line as a combination of innumerable sound sources and integrate the transmission line to calculate the audible noise at the measured point. Additionally, the audible noise with conductor-to-ground height different phases and cross angle are calculated by this method. The results indicate that the audible noise of crossing transmission lines near ground can be declined by raising the height of lines and arranging the phase and cross angle properly. Finally, the spatial distribution of audible noise of transmission lines in the crossing area can provide some reference for the design of transmission line in the future.