Question

The critical clearing time is related to
1. Steady state stability limit
2. Transient stability limit
3. Short circuit current limit
4. None of the above

Answer 1

Correct Answer - Option 2 : Transient stability limit

Critical clearing angle and time:

• It is related to the transient stability limit study of power system.
• The maximum allowable value of the clearing time and angle for the system to remain stable are known respectively as critical clearing time and angle.
• The equal-area criterion method is useful in determining the critical clearing angle, i.e., the condition when the system will be stable provided the fault is cleared before the rotor angle exceeds the critical clearing angle.
• It is not required to know about the clearing angle for stable operation of the system, but we want to know the critical clearing time corresponding to the critical clearing angle.
• Critical clearing time is the time when the rotor would have moved to the critical clearing angle.
• It helps us to design the operating times of the relay and circuit breaker so that the total time taken by them should be less than the critical clearing time for stable operation of the system.