Circuit Breaker

A circuit breaker is an electrical safety device that automatically interrupts current flow through a circuit when that current exceeds a safe level, protecting wiring and equipment from overheating and fire, and unlike a fuse it can be reset and reused rather than replaced after it trips. Thomas Edison described an early circuit breaker concept in an 1879 patent application, though his own Pearl Street power system relied on fuses instead, and the modern thermal magnetic miniature circuit breaker still found in homes today traces to a 1924 patent by Brown, Boveri and Cie, credited to engineer Hugo Stotz. By 1935 specially engineered circuit breakers built for the Boulder Dam project could interrupt faults of up to 2,500 megavolt amperes within three alternating current cycles, a major advance in handling the high voltage systems large power projects required. Circuit breakers today range from small household devices interrupting a few thousand amperes to switchgear rated above 1,200 kilovolts that protects the high voltage lines serving entire cities, making them a basic safety component at every scale of the electrical grid.