Outdoor vacuum switchgear-the state of the art

This paper outlines the design of outdoor switchgear, concentrating on vacuum interruption technology. The paper reviews a brief evolution of vacuum switchgear from the 1970´s to the present day, often in conjunction with SF₆ as insulation for outdoor use, including applications from 12 kV up to 132 kV. The historical review is important in order to understand the driving forces and evolution of this type of switchgear up to modern designs. The paper then goes on to look at the basic design aspects of outdoor vacuum switchgear, and in particular the needs and advantages of vacuum switching technology for this application. As with all technologies vacuum switchgear brings its own character to a design, and this must be taken into account by the switchgear designer. Specifically switchgear designed for transmission and particularly the distribution of power is examined, as well as a key specialist application for railway use where vacuum switchgear has dominated the application for over twenty years due to its inherent capabilities-both for traction and trackside use.