New 550-kV Gas-insulated Switchgear

OVERVIEW: Hitachi has developed smaller and more reliable gas-insulated switchgear (GIS) in response to demands for lower costs and stable power supplies. Reliability of this GIS was improved and the enclosure diameter was reduced in order to minimize the installation space by using new analysis techniques and rationalization in insulation design and in temperature rise criteria. Furthermore, the use of vertical, single-break circuit breakers and a three-phase common GIB (gas-insulated bus) reduced the substation area to 46% of its original size. A reliability test for the GIS was conducted in consideration of the service condition. The test included a limit-performance check test, a type test under hard operating conditions, a temperature-rise test at the site and factory, as well as other tests. The reliability of the GIS was improved by applying new structural design and manufacturing technologies. For example, high-precision parts and a GIS-specific assembling device were used. Large all-weather assembly houses were also used at the site and the assembly process was improved. Hirohiko Yatsuzuka Manabu Takamoto Masaharu Matsuyama