Impact of Conductor Surface Type and Rain Intensity on HVDC Corona Losses

This paper presents the results of a series of indoor laboratory experiments carried out on dc-energized overhead conductors subjected to simulated rainfall. In a first set of experiments, the impact of rain intensity on the corona onset voltage and total corona losses was investigated. With regard to the onset voltage, no significant impact was observed, whereas a weak positive correlation with total corona losses could be established. In a second set of experiments, the impact of different conductor types on the same two quantities was examined. The most notable result is that the combined use of Z-profiled-strands and sand-blasted surfaces lead to reductions in the total corona current of around 29% and 42%, for positive and negative polarity, respectively. The corresponding reduction of ground-level ion currents and ion coupling with parallel conductors is expected to be of the same order of magnitude.