Oil Circuit Breakers: A Look at the Earlier Generation [History]

In the late 19th and early 20th centuries, the interrupting media of circuit breakers were either air, oil, or water. Figure 1 depicts a collection of breakers of that vintage. The breaker shown in Figure 2 was for application at 40 kV, installed in 1901, and consisted of two barrels half-filled with water for performing interruption and oil in the upper section to provide open position dielectric. This performed fairly well until several operations were made over a short time, and it exploded, destroying the adjacent power house. Figure 3 is an oil circuit breaker (OCB) that was originally on the western Colorado power system at a voltage of 44 kV and in service for 52 years; it consisted of two barrels of oil with the interrupters and a movable current-carrying member between them.