Enhancement of linearity and constancy of PMU‐based voltage stability index: application to a Korean wide‐area monitoring system

This study presents a new wide‐area voltage stability monitoring method using synchronised phasor measurements. The salient features of the proposed index are the following: (i) It ensures constancy, which is the ability to maintain the same scale even if the system changes. (ii) It is pseudo‐linear with respect to the power system stability level, which enhances intuitiveness for real‐time operation. Accordingly, stability can be uniformly compared in various situations, and thus, the index can be used as a solid criterion or threshold point for system operation. A verification study of the proposed index with regard to constancy is carried out using Korean power system operation data. Furthermore, an implementation of the proposed method for the Korean wide‐area monitoring system is presented, and it is demonstrated that the proposed index detects event more clearly than previous stability index through an actual event measured using phasor measurement units.