The Effect of Long Term Corona Discharge on Protrusion Characteristics in C4F7N/CO2 and SF6

This study investigates the effect of long-term corona discharge on the physical and chemical characteristics of protrusion defects in high-voltage alternating current for C
4
F
7
N(13%)/CO
2
(87%) mixture and SF
6
. Corona aging tests were carried out under maintained discharge levels using a closed-loop control system. Electrode erosion was observed for both gas types, but it was slightly more significant for the C
4
F
7
N/CO
2
mixture. Furthermore, the erosion process was different from our expectations; The tips of the needle electrodes showed deposition of material and an elemental analysis revealed traces of fluorine on the surface after aging tests.