Abridgment of the structural development of the Deion circuit breaker up to 15,000 volts

UP to the present time, the interruption of an a-c. circuit has been accomplished generally in one of two ways. The arc may be drawn between contacts located in some insulating liquid such as oil. In this case, the insulating value of the oil depreciates with each current interruption until it reaches a point where it must be renewed. On the other hand, the arc may be drawn in air with no means of extinguishing it other than lengthening it to such an extent that the generated voltage is no longer able to maintain it. For modern generating voltages, this requires arcs of great length and, for the upper range of transmission voltages, results in arc lengths which are impractical. As a result of this limitation, the oil circuit breaker has assumed a position of paramount importance on modern operating systems.