Abstract :
THE RECENT PROGRESS in the electric arc furnace installation has produced improvements in virtually all phases of the installation with automatic operation and minimum maintenance of the equipment one important goal. Arc furnace switching, which is one important part of furnace operation, is generally well known for the severe duty it imposes on the switching device. Since fault protection as well as automatic switching is required, the practice has been to use a circuit breaker for both switching and protection. However, in order for the circuit breaker to withstand the mechanical duty, it has been necessary to use a circuit breaker especially designed for the purpose. Oil circuit breakers were used originally on arc furnace circuits, but because of the frequency of switching operations the oil deteriorated rapidly by carbonizing, and it was necessary to replace the oil frequently. Unless the oil was replaced, it became very likely that it would fail as an insulating medium when voltage surges appeared. These voltage surges, which are characteristic of arc furnace circuits, make it necessary that the switching equipment for such applications be one voltage class higher than the circuit in which it will operate.
