Kiyoshi Inami

Application Problems of SF6/N2 Mixtures to Gas Insulated Bus

Gas insulated bus (GIB) using SF6 gas has widely been applied in the world, because it has the advantages in reliability and in minimizing installation space. However SF6 is identified as a potent greenhouse gas and thus the efforts in preventing the release of SF6 in the environment, the study on recycling SF6and the research for alternative gas are now being performed1. in designing a GIB using alternative gas, there are many application problems such as a selection of alternative gas and its rated pressure to maintain the required dielectric and heat transfer performance. the problems on recycling SF6 are also essential in applying alternative gas using SF6 such as SF6/N2 mixtures.

Development and design of DC‐GIS

In order to realize a reliable, compact, and economical converter station for HVDC transmission, applications of gas insulated switchgear (GIS) for dc transmission lines are considered. The characteristics of dc gas insulation differ from those of ac. The behavior of metallic particles left in the enclosure is one of the largest differences. The accumulation of electrical charges on solid insulators is another essential factor in designing a DC-GIS. Also, degradation of metal oxide arrester blocks under dc stress must be deliberated. Based on the fundamental studies, we developed the components of ± 500-kV DC-GIS. Electrical and mechanical performances of these components have been tested and proven to be satisfactory. Finally these components have been assembled into a full DC-GIS and subjected to a long-term voltage endurance test. In this paper, the design philosophy of ± 500-kV DC-GIS, details of the components, and the test results are described.

Improvement of Withstand Voltage at Particle Contamination in DC-GIS Due to Dielectric Coating on Conductor

±500kV DC transmission between Honshu island and Shikoku island in Japan will be operated at the beginning of the next century. High voltage DC-Gas Insulated Switchgear (DC-GIS) equipped in the DC-AC converter station has been developed. One of considerable items for designing the DC-GIS is the effect of the particle contamination to electrical properties more crucial than conventional GIS. the particles floating around the high voltage conductor with negative DC voltage give the most detrimental effect to the insulation properties at application of positive lightning impulse. Therefore it is essential to study and elucidate the phenomena for the realization of compact and highly reliable DC-GIS.