Multiple Choo questions
Th goal of the equal area criteria in transient stability is to determine whether a system
is stable or not without having to completely integrate the system response. The
system will be stable after the fault if:
(1) The acceleration area is greater than 1.0 per unit.
(2) The acceleration area is greater than the deceleration area.
(3) The deceleration area is smaller than the acceleration area.
(4) The deceleration area is greater than the acceleration area.
Answer is (4)
Consider the behavior of a synchronous machine to some impacts due to disturbances.
At the time of occurrence of a fault, the machine will start to accelerate. When the fault is cleared, it will continue to increase speed before it reaches to its peak value (δc).
When deceleration area is greater than the acceleration area, the system will decelerate entirely before getting accelerated again. Due to the fact that the rotor inertia will force the successive acceleration and deceleration areas to become smaller than the initial values. Causing the system to reach steady state.