Sulphur hexafluoride (SF6) is mostly used as a current-insulating medium in gas-insulated switchgears (GIS), owing to its excellent dielectric strength and arc-extinguishing performance. The global warming potential (GWP) of SF6, however, is 23,900 times that of CO₂, and its life time in the atmosphere is 3,200 years. For these reasons, new eco-friendly gases to replace SF6 are required. In this study, the partial discharge (PD) characteristics of green gas for grid (g³) and dry air (N₂/O₂) were analyzed to compare with those of SF₆. A PD electrode system was designed to simulate the protrusion defect in GISs and fabricated for experimentation. To compare the PD characteristics of each gas, the discharge inception voltage (DIV), discharge extinction voltage (DEV), discharge magnitude, discharge pulse number, and phase pattern were analyzed. Results from this study are expected to provide fundamental materials for the design of eco-friendly GISs.