Gas-Insulated Switchgear (GIS) is a complete set of equipment that seals high-voltage electrical components (such as circuit breakers, disconnectors, earthing switches, instrument transformers, surge arresters, etc.) in a metal casing and fills it with insulating gas (typically sulfur hexafluoride, SF₆) as the insulating and arc-extinguishing medium.

The difference between 3-way and 4-way Ring Main Units (RMUs) lies primarily in the number of cable compartments and the configuration of the internal busbar, which directly impact flexibility, reliability, and application. Here's a breakdown:

he primary differences between Air-Insulated Switchgear (AIS) and Gas-Insulated Switchgear (GIS) in terms of international standards and commonly used voltage levels lie in their construction, insulation medium, footprint, maintenance requirements, and environmental adaptability. Below is a detailed comparison:1. Voltage Level Classification

RMU and SF6 switchgear serve different power distribution needs. RMUs are compact, medium-voltage (7.2-24kV) units ideal for urban networks, offering air/solid/SF6 insulation and ≤25kA breaking capacity. SF6 switchgear uses sulfur hexafluoride gas for superior insulation and arc quenching, handling up to 800kV/63kA in GIS systems. While RMUs are cost-effective for space-constrained applications, SF6 units excel in high-capacity scenarios but require strict gas management due to SF6's high GWP (23,500). The industry is shifting toward SF6-free RMUs and digital solutions. Choice depends on voltage needs, fault levels, space, and environmental factors.

Grid-connected voltage level standards and technical specifications for distributed photovoltaic systems in various countries worldwide