Improving DC surface flashover property in SF6 by short time fluorination of model spacers

Surface charge accumulation of high voltage direct current (HVDC) spacers can influence the surface flashover voltage and affects the reliability of the insulation systems. The cone type model spacer was manufactured based on the industrial 550 kV spacer as the prototype. The model spacers were fluorinated and tested in case of AC, DC and polarity reversal test. Experimental results of model spacers, including regular spacers and fluorinated spacers are provided. The effect of surface charges on triggering the surface flashover was discussed. The results show that the surface flashover voltage increases for the fluorinated spacer under application of both AC and DC stresses. In addition, the surface breakdown voltage of fluorinated spacers increases up to 250 kV level, compared with that of the regular spacer whose surface breakdown voltage remains at only 230 kV level.