Analysis Of Time-domain Characteristics Of Audible Noise Generated By AC Corona Discharge

With the development of economy in our country,the demand for power is growing rapidly and the voltage level of high voltage AC transmission is increasing.As a kind of corona effect,audible noise is easy to be perceived and has a significant impact on our life,which is an important reference factor for design of transmission line.The pure tone component also deserves much attention,so the further research of the characteristics of audible noise has greatly engineering significance.In this paper,firstly,time-domain waveforms of sound pressure pulses generated by alternate current(AC)corona discharge from single corona source are measured.Considering the close correlation between noise pulse and double exponential pulse,the influence of background noise is eliminated and the noise pulse is effectively extracted.Then,the statistical characteristics of pulses in the positive and negative half cycles of the AC voltage are obtained separately and the discharge interval in negative half-cycle is devided into 4 segments because the voltage changes with time constantly.The time-domain characteristics are analyzed combined with the space charge motion.The time-domain stochastic model of audible noise is established to simulate the time-domain waveform of noise.The influence of measurement time and pulse parameters on SPL and the effect of AC voltage modulation on pure tone are revealed.Furthermore,the correlation of the corona current and audible noise is analyzed.There is a one-to-one relationship between their time-domain impulses the and linear relationship between amplitude of their pulses.In their frequency domain,obvious harmonic components are both seen due to modulation effect of AC voltage,and the width of the main lobe in the spectrum is related to the width of the pulse cluster in a single period.The harmonic components below 400Hz are related to their 50Hz components linearly and the empirical formula is calculated.Finally,the audible noise and corona current generated by corona discharge form conduct are measured in time domain,and the audible noise pulse cluster is extracted through corresponding corona current cluster.The total sound pressure level(SPL)of audible noise and the value of 1/3 octave increases with the increase of applied voltage.The distribution of FFT spectrum is similar to that of corona discharge from single point,with significant pure-tone components.With the increase of voltage,the pure-tone components increase,broadening of the pulse train leads to a decrease in the cutoff frequency of the main lobe.The results obtained in this paper will help study on the mechanism of AC corona discharge and the characteristics of audible noise,as well as promote the research on the mechanism of pure tone components.