Phased Methodology for Optimal PMU Placement in Distribution Networks with Consideration of Diverse Monitoring Requirements

This paper introduces a phased PMU (Phasor Measurement Unit) placement method that adheres to the post-fault sequence of ‘perception-diagnosis-restoration’. The method enables real-time monitoring of transient and steady-state grid conditions through a phased optimization framework that addresses the objectives of voltage sag monitoring, fault location, and network reconfiguration. For voltage sag monitoring, uncertainties in photovoltaic output and fault information are accounted for, and a probabilistic voltage sag observable area is proposed to ensure observability across different scenarios. In the context of fault location monitoring, a PMU placement model is developed that requires fewer PMUs than traditional methods while still meeting fault location requirements. For steady-state monitoring, a monitoring reliability constraint ensures observability in the reconfigured distribution network. Moreover, this work reveals that the combined use of power flow measurements and zero-injection buses may fail to ensure system observability. To address this limitation, new constraints are established. The proposed method was finally validated using the IEEE 33-bus and 69-bus test systems, demonstrating its effectiveness under both transient and steady-state conditions.