Monitoring and supervision is an important aspect in view of security of an interconnected power system. The work presented here gives a comparison of various advanced state estimation techniques for optimal placement of Phasor Measurement Units in Power Networks. These techniques meet two requirements i.e. to ensure the complete system observability and at the same time find the optimal locations of Phasor Measurement Units with the minimum cost. The problem is formulated as a mono-objective optimization problem and its resolution is made by implementing seven algorithms which are mentioned in this paper. The proposed algorithms are demonstrated using five test networks that include a practical system. The simulation results ensure the complete system observability.