Transient stability analysis with equal area criterion directly used to a non-equivalent generator pair

Equal area criterion, used to transient stability analysis of power system, is consistency with transient energy function method for single machine-infinite bus system or two machines system. The criterion can be used to fast classification of transient stability, fast calculations of critical fault-clearing time and stability degree. However, machine group division and equivalence etc affect its efficiency and veracity while it is used to multi-machines system. In this paper, Equal area criterion is used to a machine couple of multi -machines system directly: two machines of best forward angle and best lag angle is selected and based on their relative power angle curve obtained by curve fitting, Equal area criterion is used to fast assessment of transient stability, fast calculations of critical fault-clearing time and stability degree. The advantage of this method is that it avoids machine group division, equivalence and network reduction, and needs less information, less computation time and it has the same accuracy as time domain simulation in assessing transient stability. Validity carried out on a test system is reported.