| The audible noise caused by the transmission lines due to the corona is a kind of audio interference and it is generated by ionization discharge of the surrounding air which can be heard by human. The issue which occurred in transmission line over500kV voltage level is an essential part of the electromagnetic environment. It not only affects the living environment of the residents near the line and determines the wire parameters, but also has great influence on the construction cost of Extreme High Voltage (UHV) grid. Therefore it’s extremely significant to study the audible noise of UHVDC transmission line especially when our country promotes the construction and development of UHVDC project vigorously.This paper firstly discussed the acoustic parameters mentioned in the experiment study and A weighted sound pressure level, equivalent continuous A sound level and acoustic spectrum are included. Secondly, the measurement and analysis methods of audible noise and the ways to deal with background noise were introduced in detail. Then based on the idea of transforming the entire line audible noise problem into the study of one-point corona discharge, this paper makes use of the frequency multiplier algorithm which describe the spatial distribution of audible noise caused by one-point sound source was derived according to GB/T17247.2-1998(Outdoor sound propagation attenuation calculation:General method of calculation). It provides a theoretical basis for the experimental study. Furthermore, considered the ground attenuation and the influence factors of atmospheric absorption, another computing method based on the basic sound equation was provided. The method can get the source pressure distribution of single point sound source in the semi-infinite space.A measurement platform for audible noise was established in an open room in order to carry out the experimental research of the work. It consists of the sound source characteristics part and the propagation characteristics part. And the accuracy of the experiments results was guaranteed by taking advantage of the known sound source to confirm the directivity of the AWA14423microphone used in the experiment. Based on the idea of transforming the entire line audible noise problem into the study of one-point and several-points ones the corona discharge experiments with tailor-made wire of one-point and several-points corona discharge were carried out in the platform. The measurement results were analyzed by mathematical and statistics methods. Then the characteristics of sound source, transverse attenuation and spectrum of the audible noise were acquired. And the excitation source model and space propagation model of the audible noise was verified by the experimental data which provided the theory evidence to predict the audible noise of the transmission lines.For further study the incidence relation between the audible noise and other corona effects associated with corona discharge, the audible noise, ionized field, ion current density and ultraviolet photon count value under the same voltage excitation were measured synchronously indoor with the noise analyzer, ionized field measuring instrument, the ion current measurement systems, ultraviolet imager separately. Finally, by mathematical analysis and statistics of experimental data the incidence relation characteristics between the audible noise and other measurement values associated with one-point and several-points corona discharge was obtained. |
