1. In power systems, stability refers to the ability of the system to:
(A) Maintain frequency at 60 Hz
(B) Return to normal operation after a disturbance
(C) Reduce transmission losses
(D) Maintain constant voltage at all buses
2. The steady-state stability limit is concerned with:
(A) Small disturbances
(B) Large sudden faults
(C) Voltage collapse
(D) Mechanical resonance
3. Transient stability deals with:
(A) Large disturbances such as faults or sudden load changes
(B) Long-term voltage variations
(C) Temperature effects
(D) Line losses
4. The main objective of stability analysis is to:
(A) Reduce generation costs
(B) Ensure synchronism between generators
(C) Control frequency deviations
(D) Improve efficiency
5. The steady-state stability limit is determined by:
(A) System parameters under small disturbances
(B) Fault clearing time
(C) Generator inertia
(D) Governor control
6. Transient stability depends mainly on:
(A) Inertia constant and fault clearing time
(B) Load demand
(C) Power factor
(D) Transformer type
7. The time frame for transient stability is usually:
(A) A few seconds
(B) Several minutes
(C) A few hours
(D) Continuous operation
8. The time frame for steady-state stability is usually:
(A) A few seconds
(B) Several minutes or longer
(C) Milliseconds
(D) Hours only
9. The transient stability of a system improves with:
(A) High inertia and fast fault clearing
(B) Low inertia
(C) Slow circuit breakers
(D) Increased transmission reactance
10. Loss of synchronism between generators is called:
(A) System instability
(B) Power factor drop
(C) Frequency deviation
(D) Load rejection
11. The most common cause of transient instability is:
(A) Sudden short-circuit fault
(B) Transformer tap change
(C) Voltage regulation
(D) Frequency drop
12. Steady-state stability can be improved by:
(A) Using voltage regulators and excitation systems
(B) Increasing load impedance
(C) Increasing fault duration
(D) Decreasing excitation voltage
13. The equal area criterion is used to determine:
(A) Transient stability
(B) Voltage regulation
(C) Frequency control
(D) Steady-state efficiency
14. Dynamic stability involves:
(A) Small disturbances over a short period
(B) Large disturbances only
(C) Long-term load changes
(D) Temperature variations
15. The inertia constant of a generator helps resist:
(A) Sudden changes in speed
(B) Voltage variations
(C) Frequency drift
(D) Load increase
16. Increasing system damping improves:
(A) Dynamic stability
(B) Voltage regulation
(C) Transient instability
(D) Power factor
17. The critical clearing time is defined as:
(A) The maximum time allowed to clear a fault without losing stability
(B) The time taken to detect a fault
(C) The duration of relay operation
(D) The breaker arcing time
18. The critical clearing angle is associated with:
(A) Transient stability margin
(B) Steady-state limit
(C) Frequency response
(D) Voltage sag
19. The system stability margin is improved by:
(A) Fast fault clearing and excitation control
(B) Increasing transmission line length
(C) Reducing inertia
(D) Delaying breaker operation
20. Long transmission lines are more prone to instability because of:
(A) High reactance and voltage drops
(B) Low impedance
(C) High capacitance only
(D) Short circuit current reduction
21. The prime mover and generator together act as a:
(A) Rotating mass with inertia
(B) Resistive element
(C) Transformer
(D) Static system
22. The excitation control system helps in:
(A) Maintaining voltage and improving stability
(B) Regulating frequency
(C) Adjusting mechanical torque
(D) Increasing line losses
23. When two alternators lose synchronism, it is called:
(A) Pole slipping
(B) Overloading
(C) Frequency regulation
(D) Power swing
24. A power swing in the system indicates:
(A) Oscillation of power flow between generators
(B) Increase in frequency
(C) Voltage collapse
(D) Constant torque operation
25. The main goal of stability enhancement techniques is to:
(A) Maintain synchronism under disturbances
(B) Reduce voltage
(C) Limit power factor
(D) Increase line impedance
26. The transient stability of the system can be enhanced using:
(A) Fast-acting circuit breakers and automatic voltage regulators
(B) Slow mechanical governors
(C) Increasing fault duration
(D) Disconnecting excitation systems
27. The governor control of a generator affects:
(A) Frequency and mechanical power
(B) Voltage magnitude
(C) Current direction
(D) Excitation level
28. Stability studies are essential for:
(A) Designing protection and control systems
(B) Reducing load consumption
(C) Transformer testing
(D) Improving insulation strength
29. A system operating close to its steady-state stability limit is:
(A) More vulnerable to disturbances
(B) More secure
(C) Always stable
(D) Less efficient but stable
30. The ultimate aim of stability analysis is to:
(A) Ensure reliable and continuous power supply
(B) Reduce transmission losses only
(C) Increase frequency stability only
(D) Improve insulation coordination