Transient Stability Analysis of Multi Machine System For Different Contingent Cases

Now a day’s power system operate closer and closer to their limits. So it makes instability in the system more probable. Due to some uncertain conditions synchronism of machines connected in system might be loss and it leads to the transient instability. Therefore Preventive control or remedial actions for transient stability enhancement should be taken if dangerous instability is detected. Assessment of transient stability of the system with considering the contingencies has to be done. Transient stability of the unhealthy system is assessed using direct approach from rotor angle of synchronous machine. For assessment the value of relative rotor angles in pre-fault, in-fault & post-fault condition has been derived. For this test two different systems (6 bus system & IEEE 39 New England system) are considered. For 6 bus system CCT (critical clearing time) analyzed for single contingency. For 39 bus system multi contingency considered.