Power System Stability-1

Q. Define stability?

Ans: The stability of a system is defined as the ability of power system to return to stable operation when it is subjected to a disturbance.

Q. Define steady state stability.

Ans: The steady state stability is defined as the ability of a system to remain stable for small disturbance.

Q. Define transient stability?

Ans: The transient stability is defined as the ability of a system to remain stable for large disturbance.

Q.What is steady state state stability limit?

Ans: The steady state stability limit is the maximum  power that can be transferred by a machine to receiving system without loss of synchronism.

Q. Define swing curve? What is the use of swing curve?

Ans: The swing curve is the plot between the power angle and time. It is usually plotted for a transient state to study the nature of variation in angle for a sudden large disturbances.

Q.Define power angle.

Ans: The power angle is defined as the angular displacement of the rotor from synchronously rotating reference frame.

Q. Define critical clearing time and critical clearing angle?

Ans: The critical clearing angle is the maximum allowable change in the power angle before clearing the fault without loss of synchronism.

The critical clearing time can be defined as the maximum time delay that can be allowed to clear a fault without loss of synchronism.

Q. Define equal area criterion?

Ans: The equal area criterion for stability states that the system is stable if the acceleration and deceleration area under power angle curve is equal.

Q. What is transient stability limit ?

Ans: The transient stability limit is the maximum power that can be transmitted by a machine to a fault or a receiving system during a transient state without loss of synchronism. The transient stability limit is always less than the steady state stability limit.