Optimal Location and Sizing of Fault Current Limiters in Mesh Networks Using Iterative Mixed Integer Nonlinear Programming

In some mature power systems located in densely populated areas, an increase in demand and supply is resulting in very high short-circuit levels that are either too close to or over the safe breaker operating limits. Fault current limiters (FCLs) built with advanced materials and methods are a potent solution in this situation wherein an in-line FCL offers a very low impedance and power loss under normal operating conditions, but a high impedance and hence a lower short-circuit current during faults. From a planning perspective for complex meshed networks where faults are concurrently fed from several sources, it is important to optimally locate and size FCLs, which is a difficult mixed integer nonlinear optimization challenge as commonly used location sensitivity index methods and heuristic search techniques seem inadequate. In this paper, an iterative mixed integer nonlinear optimization method is proposed to optimally locate and size FCLs in a power system by searching the entire solution space such that costs are the least and fault currents are curtailed to levels within breakers' limits, without prior knowledge of the best locations irrespective of the size of the system. The IEEE 9-bus, IEEE 30-bus, and a real North American 395-bus transmission system were chosen to test and demonstrate the proposed method.