Transsistent Differences In Transient Stability

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2.2 TRANSIENT STABILITY Transient stability is the ability of the power system to maintain synchronism when subjected to any transient disturbance such as the occurrence of a fault, the sudden outage or the sudden application or removal of loads. The resulting system response involves large excursions of generator rotor angles and is influenced by the nonlinear power-angle relationship. Stability depends on the initial operating state of the system and the severity of the disturbance. The system usually altered after the disturbance which may cause the system to operate in a different steady-state status from that prior the disturbance. Following such sudden disturbances in the power system, rotor angular differences, rotor speeds and power…show more content…
In transient stability studies, the study period of interest is usually limited to 3 to 5 seconds following the disturbance, although it may extend to about ten seconds for very large systems with dominant inter-area modes of oscillation (Kundur 2007). The transient instability phenomenon is a very fast one and occurs within one second or a fraction of it for generator close to location of disturbance. During the fault, the electrical power from nearby generators is reduced and the power from remote generators remains relatively unchanged. The resultant differences in acceleration produce speed differences over the time interval of the fault and it is important to clear the fault as quick as possible. The fault clearing removes one or more transmission elements and weakens the system. If the changes are such that the accelerated machines pick up additional load, they slow down and a new equilibrium position is reached. The loss of synchronism will be evident within one second of the initial…show more content…
This can occur on overhead lines or in substations where the flashover arc of the faulted phase spreads to other healthy phases (Nasser 2008). In the course of this work we investigated only a Symmetrical Three Phase (L-L-L) Fault, since roughly 5% of all faults involve all three phases and they are the most severe. For a three- phase fault, the fault impedance is zero and the faulted bus has the same impedance as the ground. (Prabha

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