Calculation and Research of Audible Noise of AC Transmission Lines (Ⅰ) - Three-dimensional Distribution

Abstract

Audible noise, as an important component of the corona effect of the wire, is one of the important indicators of environmental assessment of transmission lines. Based on a simulation charge method, we established a calculation model of the electric field strength of transmission lines considering the effect of sag. In this model, the non-uniformity of the charge distribution on the wire was taken into account. Firstly, using the conformal transformation and taking the mutual influence between the sub-conductors into account, we obtained the distribution characteristics of electric field strength along the surface of the sub-conductors, and compared with the COMSOL multi-physics simulation result at the lowest point of the internal sag of the span so as to verify the accuracy of the surface electric field strength calculation model mentioned. Secondly, combining the acoustic power generation characteristics of audible noise on transmission lines and the spherical propagation law of point sources, we divided the finite length wire into several micro line segments that can be regarded as point sources, assumed that the charge density of the wires on the micro line segment is equal, and utilized the surface field to get the distribution of the sound pressure level on the micro line segment. The three-dimensional distribution of audible noise can be obtained by integrating the line along the line. Finally, using this model, we calculated the audible noise at a distance of 20 m outside the Zhongxiang electromagnetic environment long-term observation station, the relative error between the calculated result and the actual effective rainy day statistical result is only 1.73%, which verifies the accuracy of the proposed calculation model.