REVIEW OF TECHNOLOGIES FOR CURRENT-LIMITING LOW-VOLTAGE CIRCUIT-BREAKERS

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