Recent Developments in Circuit Breakers

Sulfur hexafluoride (SF₆) circuit breakers, especially puffer-type breakers, are becoming the main equipment in switchgear for distribution voltage through the ultrahigh voltage class. A review of trends with some background history will be an aid toward a better understanding of the technology. Puffer-type SF₆ gas circuit breakers are predominantly used in gas-insulated switchgear, and their interrupting capacity has recently been increased. SF₆ circuit breakers have extended the field of application since that time supported by various improvements and developments. In most practical applications, SF₆ circuit breakers are used, and SF₆ gas is commonly used for interruption and insulation. The history of oil circuit breakers can be traced back to the experience of putting an air switch into mineral insulation oil in 1900 to cope with an increase in voltage and current. The interruption principle of air-blast circuit breakers can be classified into two major groups—the axial blast arrangement and the cross-blast arrangement.