Contaminations adhering on HVDC transmission line will change its corona characteristics to generate electromagnetic pollution. The corona-induced radio interference and audible noise become important factors influencing the configuration and costs of transmission project. For understanding the effects of contaminations on the corona pulse characteristics of an HVDC transmission line

a corona cage was adopted to experimentally investigate corona pulse inception voltage and corona pulse characteristics of the conductors with different contaminations on surfaces. The contaminations include simulated contaminations

carbon powder

cement and fine sand. The results show that when conductor is covered with contaminations

the positive polarity corona pulses have high amplitude and low frequency

while the negative polarity corona pulses have low amplitude and incremental high frequency components. The corona pulse inception voltage presents a negatively exponential decrease with the increase of contamination density

showing a saturation trend. Fine sand shows the greatest effect on the corona pulse inception voltage with positive polarity

while cement shows the least effect. A function of corona inception voltage and surface contamination density is given. This study may provide reference for design of transmission lines.