Investigations of surface charging of DC insulator spacers

Observations of the short circuit decay of both positive and negative charge carriers on PTFE spacers in dry SF₆ at room temperature were carried out in order to obtain further insight into charge behaviour on/in the polymer spacer. The influential factors such as the contact condition of the spacer with the electrode, surrounding media, and the charging method were also experimentally investigated. It was found that, (1) a good contact produces a faster decay rate; (2) the decay rate of positive charge is greater than that of negative charge under similar conditions; (3) there were obvious negative charge accumulations on the spacer near the electrode during movement toward the electrode; (4) some of the charge produced in the flashover process seem to be more stable than that produced in a non-flashover process, such as corona charging or charge injection from the electrodes