Corona current and audible noise characteristics of HVDC transmission lines and their relationship at high-altitude

The audible noise (AN) of HVDC transmission lines, as an external manifestation of the corona discharge, intensifies with the increase of altitude. In high-altitude area, the AN has been a key factor in determining the type of conductors for transmission lines. In order to study the characteristics of corona current and AN of HVDC transmission lines at high-altitude, we erected a HVDC test line at an altitude of 4300 m, and carried out AN and corona current tests under different voltages. Through the test, the basic data of AN and corona current of HVDC test line at high-altitude were obtained. Based on the corona current curve, the corona inception electric field strength of the conductor was proposed. The relationship between the equivalent A-weight sound level and the high-frequency noise component was clarified. The relational expression of the AN and corona current for the HVDC test line were suggested. The research results show that, there is a relatively fixed difference of about 7-8.3 dB between the equivalent A-weight sound level and the 8 kHz sound pressure level at altitude 4300 m, and a clear logarithmic relationship between the equivalent A-weight sound level and the average value of the corona current.