Steady State StabilityPublished on 09/2/2017 and last updated on 10/11/2018
Transient Stability: Study of power system which are subjected to sudden major disturbances. Dynamic Stability: Study of power system which are subjected to small continuous disturbances.
Steady State StabilityIt is the study which implies small and gradual variations or changes in the working state of the system. The purpose is to determine the higher limit of loading in the machine before going to lose the synchronism. The load is increased slowly.
The highest power which can be transferred to the receiving end of the system without affecting the synchronism is termed as Steady State Stability limit. The Swings equation is known by Pm → Mechanical power Pe → Electrical power δ → Load angle H → Inertia constant ωs → Synchronous speed
Consider the above system (figure above) which is operating on steady state power transfer of Assume the power is increased by a small amount say Δ Pe. As a result, the rotor angle becomes from δ0. p → frequency of oscillation. The characteristic equation is used to determine the system stability due to small changes.
Conditions for System StabilityWithout loss of stability, the Maximum power transfer is given by Assume, the condition when the system is in operation with lower than the steady state stability limit. Then, it may oscillate continuously for a lengthy time if the damping is very low. The oscillation which persists is a hazard to system security. The |Vt| should be kept constant for each load by adjusting the excitation. This is to maintain the steady state stability limit.
- A system can never be operated higher than its steady state stability limit but it can operate beyond the transient stability limit.
- By reducing the X (reactance) or by raising the |E| or by increasing the |V|, the improvement of steady state stability limit of the system is possible.
- Two systems to improve the stability limit are quick excitation voltage and higher excitation voltage.
- To reduce the X in the transmission line which is having high reactance, we can employ parallel line.