Contents I. Introduction
AN INCREASING number of power generation are installed in the power system to satisfy the rapidly growing demands for large power load. As a result, the increasing high fault current level in the grid is going above the capacity of the existing power equipment, such as circuit breakers, which may threaten the reliability and security of the power system. Under the circumstances, two methods are usually adopted by the grid company to cope with the problem. One is to replace the existing circuit breakers with the ones with large current breaking capacity, which will inevitably increase the costs. The other is to limit the fault current by using conventional current-limiting measures, which can be equivalent to integrating permanent high impedance to the power grid not only in fault condition but also in normal operation. Obviously, it results in high net loss and decrease in grid stability.
