INTERNATIONAL RESEARCH JOURNAL OF HUMANITIES,
ENGINEERING & PHARMACEUTICAL SCIENCES

Power system stability is a property of a power system that enables it to remain in a state of operating equilibrium under normal operating conditions and to remain at acceptable state of equilibrium after being subjected to a disturbance. Power system stability is broadly classified into two categories:  Angle stability  Voltage stability The rotor angle stability is the ability of interconnected synchronous machines in a power system to remain in synchronism. The angle stability problem involves the study of the electro mechanical oscillations inherent in the power systems. Voltage stability is the ability of a power system to maintain steady acceptable voltages at all the buses under normal operating conditions and after being subjected to a disturbance. The main factor causing voltage instability is the inability of the power system to meet the demand for reactive power. The angle stability problem is divided into two categories.  Transient stability  Small signal stability Transient stability is the ability of the power system to maintain synchronism when subjected to severe transient disturbance. The resulting system response involves large excursions of generator rotor angles and is influenced by the nonlinear power-angle relationship. Stability depends on both the initial operating state of the system and the severity of the disturbance. Usually, the system is altered so that the post-disturbance steady state operation differs from that prior to disturbance. Small signal stability is the ability of the power system to maintain synchronism under small disturbances. Such disturbances occur continually on the system because of small variations in loads and generation.