Question

The ‘Equal Area Criterion’ for the determination of transient stability of the synchronous machine connected to an infinite bus ________.

• A. ignores line as well as synchronous machine resistances and shunt capacitances
• B. assume accelerating power acting on the rotor as constant
• C. ignores the effect of voltage regulator and governor but considers the inherent damping present in the machine
• D. takes into consideration the possibility of machine losing synchronism after it has survived during the first swing

Hint:

Equal Area Criterion = Ideal model (ignores resistance, capacitance) + compares areas on power-angle curve for stability.

Answer 1

The Correct Option is A

Step 1: Understanding the Equal Area Criterion
The Equal Area Criterion (EAC) is a graphical method used to assess the transient stability of a synchronous machine connected to an infinite bus. It compares the accelerating and decelerating areas on the power-angle curve to determine if the system remains in synchronism after a disturbance.
Step 2: Simplifying Assumptions of EAC
To make the analysis feasible, EAC assumes:
- The system is lossless.
- No damping or resistance is present.
- The power system reactance dominates.
- Mechanical input power remains constant.
- Electrical output is a sinusoidal function of the rotor angle.
Step 3: Ignored Elements
The criterion neglects:
- Transmission line resistance
- Generator winding resistance
- Shunt capacitances
- Damping torque and AVR effects
Conclusion:
Option (1) is correct because EAC is based on idealized conditions where resistances and shunt capacitances are ignored to simplify dynamic behavior analysis.