Development of 1200-kV Compressed-Gas-Insulated Transmission and Substation Equipment in the United States

Major research and development (R&D) programs for the development of sulfur hexafluoride (SF6) compressed-gas-insulated (CGI) equipment for ultrahigh-voltage (UHV) application at 1100-1200 kV have been under way independently in both the United States and Japan. The CGI transmission and substation equipment under study and development in these countries has included the surge arrester, circuit breaker, CGI transmission bus, disconnect and ground switches, and an air-SF6 termination. The U.S. CGI program has also included development of a power transformer, shunt reactor, voltageand current-sensing instrumentation, and a line trap, all for 1200-kV application. This paper presents the overall status of development of CGI substation equipment for UHV application in the United States. It describes the major CGI components developed, highlights their key design aspects, indicates the present status of development and testing, and addresses the work remaining to establish final design concepts. The paper also includes 23 references, a number of which have not been widely distributed or included in any of the recently published bibliographies of UHV substation equipment.