Short circuit currents can be reduced in switchgears by increasing the inductive reactance seen at the fault location1. This can be done by either increasing the inductance of the circuit or by removing parts of the circuit from the fault path1. Adding reactors is one way to increase the inductance of the circuit1. Increasing the cable length is another method to minimize the fault current in a low voltage system3.Another method to reduce short circuit currents is to use short-circuit fault current limiters2. These limiters come in a variety of kinds for use in low, medium, high, and extra high voltage systems2. Some have been in service for many years, such as the traditional limited series reactor2. Other technologies, such as solid-state limiters and superconducting, have almost completed substantial research and development and are anticipated to be put to use in commercial applications soon2.Is-limiters are another technology that can be used to reduce high short-circuit currents4. This fast-acting switching device triggers a small charge to open the main conductor, which is designed to carry high operating currents4. The current commutates to a parallel fuse with high breaking capacity, which limits the short-circuit current during the first rise4. Is-limiters are being used successfully in more than 2,500 stations in 70 countries4.Coordination between circuit-breakers is another technique that can be used to reduce short circuit currents5. The technique of “cascading” uses the properties of current-limiting circuit-breakers to permit the installation of all downstream equipment with lower short-circuit breaking capacity5.
0 Comments