Metallic protrusion defects are types of defects that are easy to occur in gas insulated switchgear（GIS）equipment.Accurate detection of such defects can be achieved by partial discharge detection.This paper is aimed atmetallic protrusion defect models with different distance in SF6 gas.The experimental research on the developmentprocess under different applied voltages was carried out.The discharge pattern of different stages were measured bypulse current method.The results show that the development characteristics of partial discharges at different distanceare different. For the small distance

there are only two development stage

and for the long distance

the developmentprocess can be divided into four.When the applied voltage is close to the breakdown voltage

the discharge patternshows a double-peak characteristic of a single half cycle.The research results provide a basis for the analysis and state evaluation of the partial discharge test results of GIS equipment.