Study on the Pressure Field Reconstruction Method and Its Relationship With Audible Noise of DC Corona Discharge

DC corona audible noise (AN) is one of the electromagnetic interference from power grids and the key factors affecting the electrical design of power transmission and distribution equipment. The measurement method is crucial to study the generation mechanism of audible noise. This paper proposed a Schlieren optical measurement with a corresponding numerical reconstruction method to measure the audible noise within DC corona discharge and quantified it with the pressure field. Numerical experiments are conducted to verify the accuracy of the pressure field re-construction method. The relationship between the pressure field and sound pressure during DC corona discharge is experimentally studied. Results show that the reconstruction error is within 5%; the Schlieren system captures the gas expansion process and pressure field in the discharge region at the microsecond timescale. During corona discharge, the radial radius of the discharge region increases while its pressure decreases and overpressure increases. A relationship of non-linear proportional increase appears between the pressure field and audible noise, and only a small portion of the pressure field is converted into audible noise. The new method demonstrated in this paper is an effective way of measuring and analyzing the pressure field in the DC corona discharge, which would be the key to understanding the mechanism of acoustic wave (or AN) generation from DC corona discharge on transmission lines.