A high-capacity high-voltage three-cycle oil circuit breaker

POWER-system designers and operating engineers quite properly are constantly endeavoring to improve the quality of their services. Increases in connected capacity inevitably accentuate the demand for reducing both the frequency and the duration of interruptions in the flow of power. This is particularly true in the case of high-voltage lines which form the “backbone” of all large systems. Circuit-breaker-design engineers welcome their portion of this problem in the fulfillment of the requirement for circuit breakers having higher interrupting ratings, shorter interrupting times, and faster reclosing times. An outstanding example of this trend is found in the recent development and field testing of a 138-kv oil circuit breaker which had the following new requirements: 1. An interrupting rating of 3,500 mega-volt-amperes. 2. An interrupting time of three cycles. 3. A reclosing time of less than 20 cycles.