ABSTRACT
Gas-insulated switchgear (GIS) that uses compressed sulfur hexafluoride gas overcomes many of the limitations of the conventional open-type high voltage (HV) switchgear. The GIS enclosure forms an electrically integrated, grounded casing for the entire switchgear. The GIS enclosure can be either of the three-phase type, or of the single-phase type. The use of steel for single-phase enclosure GIS is limited to lower current densities because of the problem of electrical losses and heating in the enclosure resulting from induced circulating and eddy currents. The conductors of a GIS normally consist of aluminum tubes, the diameter and wall thickness of which depend on voltage and rated current. In addition to circuit breakers, a GIS bay includes disconnectors, voltage and current transformers, surge arresters, bushings and cable-end boxes, and gas density monitors. In the single-phase enclosed GIS, the core of a current transformer is located outside the enclosure, thus ensuring a completely undisturbed electrical field between the enclosure and the conductor.
