Ten years of progress in circuit interrupters

This is the first of a series of three related articles which together will present a review of the progress made in the past decade in the protection of electric power-system circuits and equipment This article, concerned with circuit-interrupting devices, has been prepared under the auspices of the AIEE committee on protective devices. The other two articles, dealing with protective relaying and lightning protection respectively, are scheduled for later issues Power Circuit Breakers PROGRESS in the last ten years in power circuit breakers has been rapid and has been principally along the following lines: 1. Development of increased interrupting capacity to meet the increasingly severe duties imposed by the large power concentrations. 2. Increased serviceability to permit automatic reclosing and more operations between maintenance periods. 3. Reduction of interrupting time, which increases interrupting capacity and reduces system disturbances under fault. 4. Development of ability to handle severe reclosing duty cycles at large fractions of maximum rating. 5. Improved bushing designs, increased usefulness of bushing current transformers, and the introduction of bushing potential devices for relaying and other purposes. 6. Introduction of oilless types, especially for indoor service.