Current Status of Application and Operational Experience of Alternative Switchgears using Natural-Origin Gases in Japan

SF6 alternative gases, Japan’s industry and academia have jointly worked on creating application guidelines for alternative gases and a development roadmap for alternative gas equipment, and quantitatively assessing environmental impacts. Ahead of these trends, 72/84 kV equipment designed to reduce environmental load without using SF6 had already been developed and commercialized about twenty years ago in Japan. Today, approximately 4,400 vacuum circuit-breakers (VCB) with dry air insulation and about 600 units of cubicle-type gasinsulated switchgear (C-GIS) using low-pressure dry air have been operating satisfactorily.

This paper describes the application status of equipment applying natural-origin gases (NOGs) in Japan and shares operational experience, including the long-term performance and the initial characteristic data collected during installation. The data acquisition and evaluation were conducted on dry air-insulated 72/84 kV VCB and C-GIS that have been in service for roughly 15 to 20 years. No signs of deterioration were observed, and measurements of dry air gas pressure, moisture content, and composition analysis showed no abnormalities. More recently, operations have begun for 72/84 kV VCB and gas-insulated switchgear using higher-pressure dry air, and measurements of gas pressure, moisture content, and gas composition have verified stable conditions. The operational experience with NOG equipment indicated that maintenance and installation procedures were largely consistent with those for SF6-filled equipment. The paper also presents recent efforts to extend voltage ratings from 245 kV up to 420/550 kV and to expand capacity for equipment using NOGs.