Development of a composite security index for static security evaluation

This paper proposes a composite security index for the on-line critical contingency selection and ranking in terms of both the line flow and bus voltage limit violations. In order to evaluate the vector valued security index, a scalar index is derived based on the concept of hyper-ellipse inscribed within a hyper-box. The proposed index, which provides an efficient method for filtering and ranking the credible contingencies are defined in such a way that a proper differentiation between the secure and insecure states are possible. This avoids the need for specifying any stopping criteria for contingency analysis. Test results of security evaluation using WSCC 9-bus system and IEEE 30-bus system are presented to show the effectiveness of the proposed method.