Review of technologies for current-limiting low-voltage circuit breakers

Conventional air-magnetic circuit breakers, which are widely used in low-voltage applications, utilize magnetic forces that are produced by blowout coils, the geometry of the arcing contacts, or both. The magnetic forces act to push the arc off the contacts into an arc chute, which consists of a number of metal plates. The arc chute causes the arc to be split into a number of smaller arcs, thereby facilitating the process of extinguishing the arc. In the last 20 years, the technology of circuit breakers has dramatically advanced, now including mature devices based on gas-blast (such as SF₆) and vacuum interruption. At the same time, the technology of power electronic devices has evolved rapidly, leading to suggestions of a purely static circuit breaker based on solid-state electronic devices. Recently, several different proposals have appeared for current-limiting devices to be used in conjunction with or in replacement of conventional circuit breakers. The technologies involved in these proposals have ranged from very familiar (series reactors) to quite innovative (conductive polymer devices). Several of these proposed technologies have been used to a limited extent in commercial products, but they are very likely to see increasing applications as the technology matures. This paper begins with a short review of conventional circuit breaker action for background, then reviews the recent literature for current-limiting technologies that could be applied to low-voltage electric power systems. The paper concludes with a description of work underway for further development of conductive polymer current limiters