DECOUPLED MODELS FOR LOAD FLOW AND CONTINGENCY EVALUATION.

Power system security includes security monitoring, security assessment and control. This paper deals with the security assessment aspect where effects of various credible contingencies such as faults and outages are to be evaluated by fast and reliable means, prior to the occurrence of any one of the contingencies. The paper presents the results of investigations using decoupled models both for regular load flow studies and also for contingency evaluation. Two kinds of decoupled models have been used; one is decoupled Newton load-flow and the other a modification of it. The decoupled model had earlier been used only for load flow analysis whereas in this paper, these models are successfully applied for the analysis of contingencies. The results obtained from the decoupled models have been compared with those from Newton-Raphson and Gauss-Seidal methods. The advantages of decoupled models are pointed out along with the details of convergence characteristics.