On-line monitoring, data analysis for electrolytic corrosion of ±800 kV high voltage direct current insulators

•Relative humidity has a significant effect on the amount of corrosion charge.•The amount of corrosion charge is positively correlated with the Imax per minute.•The electrolytic corrosion charge of the on-line insulators is analysed. The electrolytic corrosion of insulators’ caps and pins seriously affects their electromechanical performance; therefore, it is very important to formulate good corrosion protection measures. To investigate the electrolytic corrosion rates of insulators' metal ending fittings, six monitoring equipment for the corrosion charges was installed in different climates. The variation trends of corrosion charge with current were analysed, as well as its correlation with environmental parameters. The results show that the electrolytic corrosion rate of insulators in humid areas is much higher than that in dry areas and the amount of corrosion charge is positively correlated with the maximum corrosion current per minute. Relative humidity has a significant effect on the amount of corrosion charge, and with the increase of corrosion rate, the effect of relative humidity on corrosion becomes more and more significant. The study conclusions will provide a basis for formulating metal corrosion protection measures for insulators.