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

SF6 gas has excellent dielectric strength and interruption performance. For these reasons, it has been widely used for gas‐insulated switchgear (GIS). However, use of SF6 gas has become regulated under agreements set at the 1997 COP3. Thus, investigation and development for GIS with a lower amount of SF6 gas are being carried out worldwide. Presently, SF6‐free GIS has been commercialized for the 24‐kV class. Air or N2 gas is used as the insulation gas for this GIS. On the other hand, SF6‐free GIS has not been commercialized for the 72‐kV‐class GIS. The dielectric strengths of air and N2 gas are approximately one‐third that of SF6 gas. To enhance the insulation performance of air and N2 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 SF6‐free GIS. This paper deals with key technologies for SF6‐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. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(4): 13–23, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20451