A new method for operating point free power system transient stability situational awareness based on single machine equivalent approach

Abstract

Transient stability assessment is an essential element for situational awareness and decision making process of a power system operator in maintaining the secure operation. Continuous efforts have been made for devising methods to assess the transient stability. However, the existing methods have dependency on pre-fault operating condition. This article aims to report a new method, towards deriving contingency wise operating point free transient stability assessment. The method is based on single machine equivalent (SIME) approach and has two phases (a) off line tuning (b) online application. In offline tuning phase each plausible contingency is characterized by an operating point free parameter called mean critical return angle over the specified operating region. In online application phase, transient stability for a given plausible contingency is predicted using SIME approach. Two new severity indices namely stable severity index and unstable severity index are proposed and evaluated for assessing the degree of stability and instability. Further, these indices are used in contingency screening. The proposed method is tested on 3-machine 9-bus system and, 10-machine 39-bus system. Resultsshows that the proposed method is simple and can aid the existing methods in providing reliable transient stability situational awareness to the system operator.