The characteristics of partial discharge from particles in GIS

The characteristics of partial discharges (PDs) generated by metallic particles in compressed SF₆ have been studied. PD measurements have been obtained under AC stress in a uniform electric field configuration, with a protrusion that allowed one to measure directly the true PD pulse charge. Several gap configurations have been considered among which dielectric surfaces have been placed in the proximity of the protrusion, to study the effect of spacers on PD activity. Different measurements were carried out including phase resolved partial discharge analysis. An interpretation of the data is given, based on previously published discharge models and a tentative explanation of some physical mechanisms is presented. Moreover an approximate scaling law has been verified, which relates the PD charges to the experimental parameters (protrusion dimensions, gas pressure and electric field). The phase distribution of the PD pulses is presented and discussed