PMU based observability reliability evaluation in electric power systems

• The optimal PMU places may lose observability in various system outages.
• A reliability index is suggested to quantify the observability reliability of power systems.
• The index is associated with PMU and transmission branch outages.
• The index shows the reliability of gathering data from PMUs.
• The paper finds the best among the multiple optimal solutions of PMU placement.

This paper proposes a new reliability index to quantify the observability reliability of power systems associated with phasor measurement unit (PMU) and transmission branch outages. The proposed index can be used to determine the most reliable PMU placement in the multiple optimal solutions that all guarantee full system observability. The studies are carried out for three cases: (a) optimal PMU placement for full observability in the normal state; (b) optimal PMU placement for full observability under N − 1 conditions of transmission branch and PMU failures; and (c) optimal PMU placement to ensure that the system observability reliability meets a pre-specified threshold. The simulation results for the IEEE 14-bus system and New England 39-bus test system demonstrate the effectiveness of the proposed concept of observability reliability, loss of data expectation index and its evaluation.