Audible noise is closely related to corona current on a high voltage direct current (HVDC) transmission line. In this paper, we measured a large amount of audible noise and corona current waveforms simultaneously based on the largest outdoor HVDC corona cage all over the world. By analyzing the experimental data, the related statistical regularities between a corona current spectrum and an audible noise spectrum were obtained. Furthermore, the generation mechanism of audible noise was analyzed theoretically, and the related mathematical expression between the audible noise spectrum and the corona current spectrum, which is suitable for all of these measuring points in the space, has been established based on the electro-acoustic conversion theory. Finally, combined with the obtained mathematical relation, the internal reasons for these statistical regularities appearing in measured corona current and audible noise data were explained. The results of this paper not only present the statistical association regularities between the corona current spectrum and the audible noise spectrum on a HVDC transmission line, but also reveal the inherent reasons of these associated rules.
Corona inception voltage is of great significance for the design of ultra‐high‐voltage direct current transmission lines. In this study, based on the change rule of frequency‐domain characteristics of corona current, a new method for calculating corona inception voltage is proposed. First, corona current waveforms are collected through experiments and the range of measuring voltages is determined according to the frequency spectrum characteristics of corona current. Then, the curves representing the relationship between the change rate of corona current octave power and the voltage at different centre frequencies (6–20 kHz) are obtained through least‐square fitting. The voltage at which the fitted curve reaches the first peak value with the rise of voltage is identified as corona inception voltage. Finally, with the proposed method, the corona inception voltage for a six bundled conductor system in the biggest outdoor corona cage of the world is obtained. Combined with the experimental results of A‐weighted sound level of audible noise, the comparisons between the obtained corona inception voltage and that calculated with I/U−U curve fitting method, I−U curve fitting method and an audible noise‐based method prove that the proposed method is reasonable.
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