Security distance for distribution system: Definition, calculation, and application

Summary This paper proposes the definition, calculation, and application of security distance for distribution system. Firstly, state space is divided into N‐1 security region, sub–security region, and insecurity region considering N‐1 contingency. Security distance is the distance from an operating point (state) to the boundary of the security region. Secondly, two types of distances, ie, geometric distance and state distance, in state space are defined. Then 18 specific security distances are defined and calculated using two‐step method based on DC and AC power flow. Thirdly, the application of the proposed security distances on security analysis is presented, including security check, security evaluation, and cross‐boundary analysis. The most insecure directions and security control schemes with minimum cost can be found by the cross‐boundary analysis. Finally, case studies are presented to illustrate and verify the effectiveness of the proposed security distances. In this paper, security distance for distribution system is systematically developed, and the cross‐boundary analysis method enriches the existing security analysis.