Determination of Optimal Number and Placement of Phasor Measurement Units (PMU) in Transmission Networks

Abstract

With power demand in the world escalating day by day, interconnected power system networks are becoming progressively complex. Therefore, it is necessary to monitor and control operation of the system more accurately for smooth operation of the system. The classical state estimation of power system is based upon measurements collected from Supervisory Control and Data Acquisition System (SCADA), which is inadequate to measure fast and dynamic phenomenon. Phasor Measurement Unit (PMU) provides real time and synchronized phasor measurements with the use of Global Positioning System (GPS) with great measurement accuracy. However, placement of PMU at each and every node of the system is economically and technically not viable. Hence, PMUs are optimally placed in the network using Recursive Security N (RSN) algorithm, ensuring system's full observability and maximum reliability. Three step RSN algorithm is coded in MATLAB and utilized here to optimally place PMUs in Integrated Nepal Power System (INPS), considering presence of ZI buses. Then, System Observability Redundancy Index (SORI) was calculated for the obtained sets of optimal solution to ensure that the solution is most reliable among obtained sets. Further, to ensure validity of the method, it is implemented in IEEE 14-bus, 30-bus and 57-bus system. In INPS, 2 sets of optimal solution with 21 number of PMUs was determined. Using the same algorithm, a set of optimal solution with 3 PMUs, 4 sets of optimal solution with 7 PMUs and 2 sets of optimal solution with 12 PMUs was determined for IEEE 14-bus, 30-bus and 57-bus system. Finally, SORI is calculated for each case and the solution set that offers maximum SORI was selected. Maximum SORI for 30-bus, 57- bus and INPS was found to be 33, 54 and 82 respectively.