Power System Analysis MCQs

 

Power System Analysis MCQs

Q1. The main objective of power system analysis is:
A) To reduce cost of generation
B) To minimize transmission loss
C) To analyze performance under various operating conditions
D) To increase voltage levels
Ans: C

Q2. In a power system, per unit (p.u.) values are mainly used because:
A) They simplify analysis
B) They increase accuracy
C) They reduce cost
D) They improve protection
Ans: A

Q3. The per-unit value of any quantity is defined as:
A) Actual value × Base value
B) Base value ÷ Actual value
C) Actual value ÷ Base value
D) Actual value + Base value
Ans: C

Q4. Kron’s reduction method is used for:
A) Reducing buses in a power system network
B) Load flow analysis
C) Short-circuit analysis
D) Transient stability
Ans: A

Q5. Y-bus matrix is:
A) Symmetric
B) Skew symmetric
C) Diagonal
D) Non-symmetric
Ans: A

Q6. The diagonal elements of Y-bus are known as:
A) Self-admittance
B) Mutual-admittance
C) Transfer-admittance
D) None of these
Ans: A

Q7. In Gauss-Seidel method, acceleration factor is used to:
A) Improve convergence
B) Slow down iteration
C) Reduce error
D) None
Ans: A

Q8. Which method is best suited for large power system load flow?
A) Gauss-Seidel
B) Newton-Raphson
C) Z-bus method
D) Gauss elimination
Ans: B

Q9. The Jacobian matrix in Newton-Raphson load flow consists of:
A) Partial derivatives of active and reactive power with respect to bus angles and voltages
B) Power loss terms only
C) Voltage magnitudes only
D) Admittance matrix terms only
Ans: A

Q10. The swing equation of a synchronous machine is used for:
A) Steady state stability
B) Transient stability
C) Load flow analysis
D) Short circuit analysis
Ans: B

Q11. Steady state stability limit is:
A) Maximum power transfer limit without losing synchronism
B) Minimum power transfer limit
C) Equal to surge impedance loading
D) None
Ans: A

Q12. Surge impedance loading (SIL) of a transmission line depends on:
A) Line length only
B) Line resistance only
C) L and C of the line
D) G and R of the line
Ans: C

Q13. Equal area criterion is used for:
A) Small signal stability
B) Steady state stability
C) Transient stability
D) Voltage stability
Ans: C

Q14. The maximum power transfer occurs when:
A) Load impedance = Line resistance
B) Load impedance = Source impedance
C) Load reactance = Source reactance
D) Source impedance = Zero
Ans: B

Q15. Short circuit MVA is equal to:
A) Base MVA ÷ p.u. reactance
B) Base MVA × p.u. reactance
C) Base kV ÷ Base MVA
D) None
Ans: A

Q16. A PV bus in load flow study is known as:
A) Slack bus
B) Generator bus
C) Load bus
D) None
Ans: B

Q17. In load flow, slack bus is used to:
A) Balance active and reactive power
B) Supply only reactive power
C) Maintain constant load
D) Maintain zero losses
Ans: A

Q18. The Newton-Raphson method in polar form is preferred over rectangular because:
A) It requires less memory
B) It gives faster convergence
C) Jacobian is simpler
D) More accurate
Ans: B

Q19. Symmetrical fault analysis assumes:
A) Equal fault current in all phases
B) Unequal fault current in phases
C) Open circuit fault
D) None
Ans: A

Q20. Unsymmetrical faults are analyzed using:
A) Z-bus method
B) Sequence components
C) Kron reduction
D) Load flow
Ans: B

Q21. The most severe fault in a power system is:
A) Single line-to-ground
B) Double line-to-ground
C) Line-to-line
D) Three-phase
Ans: D

Q22. The positive sequence network represents:
A) Balanced system operation
B) Negative sequence faults
C) Zero sequence components
D) None
Ans: A

Q23. The zero-sequence impedance of a transmission line depends on:
A) Earth return path
B) Positive sequence impedance
C) Transformer tap settings
D) Surge impedance
Ans: A

Q24. The value of X/R ratio in short circuit studies is important because:
A) It affects circuit breaker rating
B) It affects line charging
C) It reduces voltage drop
D) None
Ans: A

Q25. A line is said to be short if its length is less than:
A) 50 km
B) 80 km
C) 100 km
D) 150 km
Ans: B

Q26. A long transmission line is modeled using:
A) π-model
B) T-model
C) Distributed parameter model
D) None
Ans: C

Q27. In economic load dispatch, the objective is:
A) To minimize cost of generation
B) To minimize system loss
C) To minimize voltage drop
D) To improve stability
Ans: A

Q28. Penalty factor in economic dispatch accounts for:
A) Transmission losses
B) Generator fuel cost
C) Reactive power losses
D) Transformer losses
Ans: A

Q29. Optimal load dispatch is obtained when:
A) Incremental fuel cost of all units is equal
B) Minimum fuel cost is used
C) Maximum power transfer occurs
D) Load is minimum
Ans: A

Q30. Power angle δ is the angle between:
A) Rotor axis and stator axis
B) Voltage and current
C) Infinite bus voltage and generator voltage
D) None
Ans: C

Q31. If the load angle δ increases beyond 90°, the machine:
A) Remains stable
B) Becomes unstable
C) Transfers more power
D) Operates at unity power factor
Ans: B

Q32. Ferranti effect is observed in:
A) Long unloaded transmission line
B) Short loaded line
C) Transformers
D) Short circuit
Ans: A

Q33. The main cause of Ferranti effect is:
A) Line capacitance
B) Line inductance
C) Line resistance
D) Corona
Ans: A

Q34. Corona loss increases with:
A) Decrease in frequency
B) Decrease in voltage
C) Increase in supply frequency and voltage
D) Decrease in conductor diameter
Ans: C

Q35. The surge impedance of a line is:
A) √(L/C)
B) √(C/L)
C) L/C
D) C/L
Ans: A

Q36. For maximum power transfer in a line:
A) Pmax = EV/X
B) Pmax = EV/X × sinδ
C) Pmax = EV/2X
D) None
Ans: A

Q37. Real power transfer depends on:
A) Line resistance
B) Line capacitance
C) Angle δ
D) Reactive power only
Ans: C

Q38. Reactive power transfer depends mainly on:
A) Voltage magnitude difference
B) Phase angle difference
C) Resistance
D) Power factor
Ans: A

Q39. In power system stability studies, small-signal stability is due to:
A) Eigenvalue analysis
B) Equal area criterion
C) Load flow
D) Fault analysis
Ans: A

Q40. Reactive power compensation improves:
A) Stability
B) Voltage profile
C) Transmission efficiency
D) All of these
Ans: D

Q41. FACTS devices are mainly used for:
A) Real power compensation
B) Reactive power control and stability improvement
C) Voltage reduction
D) Frequency control
Ans: B

Q42. HVDC transmission is preferred for:
A) Short distance, high power
B) Long distance, bulk power
C) Low voltage networks
D) Small loads only
Ans: B

Q43. The main advantage of HVDC is:
A) No skin effect
B) Reduced corona
C) Reduced transmission losses and stability improvement
D) All of these
Ans: D

Q44. In load flow, PQ bus is:
A) Load bus
B) Generator bus
C) Slack bus
D) None
Ans: A

Q45. Bus admittance matrix is mainly used in:
A) Load flow analysis
B) Economic dispatch
C) Stability study
D) Fault analysis
Ans: A

Q46. Z-bus building algorithm is used for:
A) Short circuit analysis
B) Load flow
C) Economic dispatch
D) Ferranti effect
Ans: A

Q47. A three-phase balanced system has:
A) Only positive sequence components
B) Only negative sequence
C) Only zero sequence
D) All three sequences
Ans: A

Q48. Negative sequence components cause:
A) Heating in rotor of synchronous machine
B) Overvoltage
C) Reduced corona
D) Increased SIL
Ans: A

Q49. In transient stability analysis, critical clearing time means:
A) Maximum time fault can persist without loss of synchronism
B) Minimum fault clearing time
C) Time for steady state to re-establish
D) None
Ans: A

Q50. Power system oscillations after disturbance are mainly:
A) Damped
B) Undamped
C) Growing oscillations
D) None
Ans: A