Phasor measurement units (PMUs) are considered as a promising tool for future monitoring, protection and control of power systems. One of the applications of phasor measurements is state estimation. The first step in state estimation is to gather measured data from different substations in a power network. These measurements must be sufficient to make the system observable. This book adopts three algorithms for minimizing the size of the PMU configuration while allowing full observability of the network; Depth First Search (DFS), Simulated Annealing (SA) and Minimum Spanning Tree (MST) algorithms. The applied methodologies included the system observablility during normal operating conditions, as well as single branch forced outages in order to obtain a reliable system. The book also adopts two efficient heuristic techniques for optimal PMU placement; Greedy algorithm and Single Vertex Algorithm. To verify the effectiveness of the introduced algorithms, comparative studies are conducted on four test systems with encouraging results. The obtained results are compared with the results of other approaches from literature to demonstrate the effectiveness of the applied methods.