Development of 72-kV high-pressure air-insulated GIS with vacuum circuit breaker

Abstract

SUMMARYSF 6 gas has excellent dielectric strength and interruption performance. For these reasons, it has been widely used for gas-insulated switchgear (GIS). However, use of SF 6 gas has become regulated under agreements set at the 1997 COP3. Thus, investigation and development for GIS with a lower amount of SF 6 gas are being carried out worldwide. Presently, SF 6 -free GIS has been commercialized for the 24-kV class. Air or N 2 gas is used as the insulation gas for this GIS. On the other hand, SF 6 -free GIS has not been commercialized for the 72-kV-class GIS. The dielectric strengths of air and N 2 gas are approximately one-third that of SF 6 gas. To enhance the insulation performance of air and N 2 we have investigated a hybrid gas insulation system which has the combined features of providing an insulation coating and suitable insulation gas. We have developed the world's first 72-kV SF 6 -free GIS. This paper deals with key technologies for SF 6 -free GIS, such as the hybrid insulation structure, a bellows for the high-pressure vacuum circuit breaker, a newly designed disconnector and spacer, and prevention of particle levitation. Test results of the 72-kV high-pressure air-insulated GIS with the vacuum circuit breaker are described.

Improvement of insulation performance of solid/gas composite insulation with embedded electrode

“…In these days, most of the medium voltage switchgears are the cubicle-type low pressure SF6 gas insulated switchgears (C-GIS). However, SF6 gas was designated as one of the targets of emission control in the global warming prevention conference held in 1997 (COP3), then research and development of SF6 gas free systems are advanced actively [1][2][3][4][5][6]. In the medium voltage class, the switchgears insulated with high pressure air or nitrogen has been developed [3] On the other hand, research and development of technological components aiming for the realization of a full solid insulated substation is advanced actively in the extra high voltage class.…”

Development of a high‐pressure air‐insulated 72/84‐kV disconnecting switch corresponding to bus‐transfer current switching

“…The shield and moving contact had the same outer diameters as disconnectors for SF 6 gas-insulated GIS [5]. Arc guards (boron-containing polytetrafluoroethylene) were placed on the fixed shield tip, thus preventing arcing.…”

“…Although the dielectric strength of air is only about 1/3 against that of SF 6 gas, its insulating properties can be improved substantially by means of high pressure and gas/solid hybrid insulation [4]. The authors showed that GIS of conventional size can be implemented using air insulation, and developed a 72/84-kV SF 6 gas-free GIS [5]. However, although that SF 6 gas-free GIS was of the same size as conventional GIS, it supported only a single bus.…”

Study on oxygen/nitrogen gas mixtures for the surface insulation performance in gas insulated switchgear

“…Recently, Sato et al [23] developed a solid insulated switchgear (SIS) in which an epoxy casting material was used for solid insulation. Furthermore, researchers [5,11,24,25] have examined gas insulated switchgears (GIS) in which solid insulation and dry air were used. The gaseous insulation media and insulation methods of these ecofriendly composite insulation devices were eco gases (i.e., vacuum and air) and composite insulation with solid insulation respectively.…”

“…Thus, it is required to study the performance and reliability of surface insulation in the eco gases for SIS and GIS. Precedent researchers have studied on the selection of eco gases with respect to low global warming potential [4,10,11] and insulation properties on an electrode [4,5,[24][25][26][27]. These studies have only focused on the insulation characteristics of the eco gases and on the insulation method using the coated electrode in order to compensate their dielectric strength which was lower than the dielectric strength of SF 6 .…”