Optimal PMU placement to ensure system observability under contingencies

Optimal placement of Phasor Measurement Units (PMUs), to ensure complete observability of power system, should not only be decided at the base case operating conditions but also must consider the contingency cases. This paper presents a simple and effective method for optimal placement of PMUs considering critical contingencies. A voltage stability based contingency screening method has been utilized to select critical contingency cases. An Integer Linear Programming (ILP) based algorithm for the PMU placement has been modified to determine optimal PMU locations under the system intact and the critical contingency cases. The proposed method is tested on the IEEE 14-bus system, New England 39-bus system and Northern Region Power Grid (NRPG) 246-bus Indian system and the test results have been compared with three more modified PMU placement methods viz. depth first search, direct spanning tree and direct N-1 spanning tree methods.