Avoiding extended failures in large interconnected power systems — Theoretical and practical issues

This paper is treating the problem of correct and complete analysis of a large interconnected power system by evaluating the extended failures occurrence probability. Both theoretical and practical issues are treated from the perspective of complete periodically computations that have to be performed in order to have a clear image about the security margins available in a power system for a given stage of time. Main aspects related with steady-state stability limits and transient stability limits are presented from a practical point of view. The key aspects of the well known approaches related with the steady-state stability limits (SSSL) computation is reviewed and an algorithm for SSSL identification, developed by the authors in order to be fitted for power systems planning and operation is also described. The benefits of using a practical methodology to assess the transient stability margins in a real power system are going to be also presented. In order to cover this, the main theoretical aspects related with transient stability are described from a practical point of view. The paper highlights a methodology to assess the risk of a blackout in a power system by means of static and dynamic simulations using a dedicated software tool. Proposed methodology covers both SSSL and transient stability limits (TSL). Original aspects of the paper consists in a new approach to compute the SSSL on a specific constrained area in a power system as well as in a practical method to assess TSL for a given maximum loading of the analyzed power system.