Measurement And Analysis Of The Time-domain Characteristics Of Audible Noise In The Close Distance From Corona Discharge Of HVDC Lines

With the increase of voltage of HVDC transmission lines, more and more attentions are focused on the electromagnetic environment problems of transmission lines. Audible noise (AN) can be heard directly. The effect of AN receives more attention. There for, AN is a question need to be solved quickly. The thesis makes in-depth research on time-domain characteristics of AN caused by DC corona, to further understand its intrinsic characteristics.The thesis mainly contains the following three parts. Firstly, in order to ensure that the accurate measured data from close distance for AN, the thesis conducted some experimental and theoretical researches on how to select the measurement distance for AN from DC corona. The experiments were conducted in the anechoic chamber to reduce the influence of the background noise. In the experiments, the frequency sweeping method is employed, the measurement and theoretical values of sound pressure at different frequencies and different measurement distance are compared and the accurate measurement range for AN was obtained. Secondly, the thesis conducted some measurements of the time-domain characteristics of AN from DC corona. The experiments included single corona sources with different size of the discharge point and different conductor, two corona sources at different distances and multiple corona sources. The time-domain characteristics of AN are carefully analyzed and some conclusions can be drawn. The study found that the diameter of wire and the size of point are negative correlation with AN. When there are multiple corona points and multi-space is small, there are interactions between discharge points. With the increase of the number of discharge points, the pulse rate of AN pulses turns to be higher gradually. Lastly, expounds a method of transfer the measured data of time-domain to frequency-domain sound pressure level analysis, in order to compare the laboratory experimental results with the engineering data. This method can transfer time domain results into sound pressure level in frequent domain on the basis of the principle of sound level meter and characteristics of the AN caused by DC corona.