Abstract: Monitoring of system operation conditions is essential for secure operation of power systems. This is traditionally accomplished by state estimators which provide creditable data from raw data acquired from measurement devices. Measurement devices of state estimators may vary from power flow/injection and voltage/current magnitude to phasor measurement unit (PMU). On the other hand, observability is fundamental part of state estimators. Four kinds of observability algorithms are used in state estimators; algebraic, numerical, topological and hybrid. This paper aims to provide a survey of topological observability algorithms. To do this, such algorithms are firstly classified into conventional and PMU based. Then, related studies are investigated and summarized. It is observed that PMU based algorithms are computationally more simple, systematic, and efficient than conventional ones.

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