Repetitve nanosecond impulses in gas-insulated metal-enclosed switchgear (GIS) are likely to trigger inside flashover. Interface charges on the spacer in GIS are considered one of the main factors damaging insulation performance and may be induced by overvoltage. For good understanding of insulation failures

accumulation characteristics of charges between SF

6

and epoxy spacers under repetitive nanosecond impulses are investigated. It can be found under nanosecond impulses

the charge source in gas volume contributes to interface charge accumulation predominantly. Interface charges will be promoted by impulse number and amplitude. Accumulation processes are analyzed based on runaway electrons mechanism. When impulse amplitude exceeds a threshold value

discharge in the gas volume turns to a runaway mode. A runaway electron leads to the interface charge accumulation. Affected by motion of the runaway electrons

the potential peak gradually moves close to the grounded electrode when impulse amplitude is raised. Meanwhile

increasing impulse number can enhance surface potential. Surface potential will reach saturation eventually. H

owever

memory effect of the repetitive impulse discharge makes the half-peak width of the surface potential at the interface change little. Design of GIS gas-solid insulations can refer to this research.