Operating Experience with High-Speed Oil Circuit Breakers

This paper outlines the experience of the New York, New Haven and Hartford Railroad with three high-speed oil circuit breakers which were installed in 1925 to serve an electrified branch line carrying freight and passenger traffic, both local and through. Satisfactory operation of paralleling commercial communication circuits, as well as of its own, presented an immediate problem, which after study outlined in the paper, finally yielded, and the answer, in part, was high-speed circuit breakers. The electrical and mechanical characteristics of these are set forth in detail and illustrated. A number of tests of the circuit breakers and communication circuits made by short-circuiting the 11,000-volt lines on the branch showed currents up to 3000 amperes, and openings in from one-half to one and one-half cycles, with satisfactory operation of commercial and railroad communication plant. A detailed record of the service operations of the circuit breakers along with a statement of failures is given. It is proper to say that the latter were more numerous in the early days of their use than they have been in recent months, and that a number of the faults are chargeable to the railroad´s urgent need for the equipment, thereby considerably limiting the development and testing time desired by the manufacturer. While it was not discussed in detail in the paper it goes without saying that in the design and installation of the circuit breakers safety was a paramount consideration.