Switching of Extra-High-Voltage Circuits III-Design of Air Blast Circuit Breakers

A line of outdoor air blast circuit breakers is described for ratings through 700 kv. These breakers are of a modular or building-block design and are an extension of an existing 115-345-ky line. They include resistors for preinsertion during circuit closing to minimize switching surges and are designed to handle the high charging current values of line dropping and the high recovery rates expected during power faults on transmission lines of extra-high-voltage (EHV) high capacity systems. The technical problems of EHV transmission impose numerous design criteria on power circuit breakers for these systems and do not permit the simple extrapolation of requirements from breaker designs of lower transmission voltages. Breaker development has paralleled the development of a new compound circuit test facility capable of proving its EHV high capacity abi1ity.