Notes on oil circuit breakers for large powers and high potentials

The paper gives a brief outline of some of the important developments in oil circuit breakers which have taken place within the last two or three years. Ideal conditions require that the current should not reestablish itself after passing the first zero value following the opening of the contacts, and this emphasizes the value of high opening speed in a circuit breaker. Breakers have been designed in which resistances were introduced to limit the current to a value readily ruptured, but as this principle is difficult of accomplishment, reactance has been successfully substituted for resistance. Reactance breakers have two sets of contacts, the main set which carries the normal current, and an auxiliary set which carries the reduced current after the reactance has been introduced by the opening of the main contacts. Breakers for any power and voltage, with all the usual methods of operation are now available.