DYNAMIC SINGLE-MACHINE EQUIVALENT TECHNIQUES FOR ONLINE TRANSIENT STABILITY ASSESSMENT

According to the post-fault trajectory duration characteristics, power system disturbances, which may cause transient stability problems, ar e classified into three types: short, long and extremely long duration ones. An improved method using dynamic single machine equivalent syst em (SMES) model for on-line first swing critical clearing time (CCT) e stimation for both short and long duration disturbances on multi-machi ne power systems is developed in this paper. This dynamic SMES model s ubstitutes for a large power system to provide fast, on-line transient stability assessment (TSA). Techniques such as assessment of energy m argin, identification of a group of machines called the 'dominant crit ical machines' and an interpolation formula for CCT evaluation are pro posed in this method to achieve high speed and accuracy in TSA. Test r esults on real size power systems are reported to show that the method is reliable for CCT assessment of both short and long post-fault dura tion disturbances. (C) 1996 Elsevier Science S.A.