Surface aging effects of long-term energized conductors on spectrum characteristics of audible noise

The impact of surface aging level of long-term energized conductors on spectrum characteristics of audible noise is studied in this paper. It is found that the average roughness and root-mean-square roughness of conductors increase with the operating time, namely the aging degree, through the quantitative measurement. A-weighted equivalent continuous sound pressure level (LAeq) is found to increase with the aging level. As the aging aggravation, the LAeq and its high-frequency components (>1 kHz) increase substantially and high-frequency components are mainly contributing to the increasing of LAeq. The high-frequency components (>1 kHz) of the new and aged stranded conductors have a marked increasing trend as the surface potential gradient increases, while the low-frequency components are mainly environment noise.