The recent development of phasor measurement units (PMUs), enhancing synchronization and high time-resolution of measurements, allows the creation of dynamic snapshots and makes network real-time observability possible. A proposed analysis of power system observability and the rules of PMUs placement with the aim of linear static state estimation (SE) of power system networks are presented in this paper. According to the Power System Analysis Toolbox (PSAT), MATLAB toolbox, several algorithms of PMUs allocations as well as their differences and relations are introduced such as a graph-theoretic procedure based on Depth First Search, Simulated Annealing Method, Minimum Spanning Tree Method, and others. These different methods are used to benchmark the real networks with different scales, topologies and voltage levels in Egypt besides the standard test systems of IEEE 14-bus and IEEE 30-bus. The obtained results indicate the effectiveness of the applied methods of optimal PMUs placement for power system observability with the aim of linear static SE as well as the further requirements for optimal PMUs placement, which are not provided by any of the different methods for future work. By comparing the studied methods, we found that, it could not be said that there is an algorithm is optimal for all cases.