Positive corona discharge and acoustic characteristics of stranded conductor under low air pressure and different humidities

•DC transmission lines can produce severe corona discharge and audible noise (AN) at high altitudes.•A climate tank test platform with adjustable air pressure and humidity was built in the paper.•The corona current pulse and AN data in the humidity range of 45 % to 90 % and the air pressure range of 78.9 to 56.04 kPa were obtained.•AN level increased significantly with decreasing air pressure and with increasing relative humidity, the changes were small. DC transmission lines can produce more severe corona discharge and audible noise (AN) at high altitudes than that in low elevation areas, which is an important factor to be considered in line erection and selection. Besides, the humidity can also affect the performance of corona discharge and AN level. In this paper, a climate tank test platform with adjustable air pressure and humidity was built, and the characteristics of positive DC corona discharge and AN level of stranded wire conductor were investigated. The corona current pulse and AN data in the humidity range of 45 % to 90 % and the air pressure range of 78.9 to 56.04 kPa were obtained, and the variation were analyzed. It is found that, as the air pressure decrease, the A-weighted AN level increase clearly. With the increase of relative humidity, the A-weighted AN level fluctuated, but the change is relatively small.