Purpose/Aim
As a key component of DC GIL, basin spacers have experienced repeatedly random surface discharge along the surface polishing area, which seriously threatens the reliable operation of GIS/GIL. It is necessary to investigate the influence of surface polishing on surface charging and flashover characteristics of spacer in GIS/GIL under DC condition.
Experimental/Modeling methods
To investigate the influence of surface polishing on surface charging and flashover characteristic, the basin spacers were treated with circumferential and radial polishing. The surface charge distribution of untreated and polished spacers were measured after 1 hours’ voltage application of ± 15 kV. The surface flashover voltages under DC, DC pre-voltage were compared and analyzed. The changes of surface morphology before and after polishing treatment were measured by SEM and EDS.
Results/discussion
The results show that large amount of homo-polar charges are accumulated on the untreated spacer surface. However, more accumulated heteropolar charges were observed on the polished area and outward expansion area. Polishing orientation has an effect on the flashover voltage. Compared with circumferential polished spacer, the flashover voltage of radial polished spacer decreased obviously. The flashover voltage of the radial polished spacer decreased 11% under positive pre-loading condition.
Conclusions
The correlation between the polishing orientation and the surface charge accumulation was investigated. It is confirmed that micro discharge caused by the change of surface morphology is responsible for heteropolar charge accumulation on the polished area.
 

polishing,gil,spacer,surface charge