Fault Studies and System Performance — MCQs – EE

1. The main objective of fault studies in a power system is to:
(A) Measure load flow
(B) Determine fault currents and voltage levels during abnormal conditions
(C) Calculate efficiency of transmission lines
(D) Control frequency variations

2. A fault in a power system is defined as:
(A) Any abnormal condition in the electrical network
(B) A system overload
(C) A voltage increase
(D) A power loss in conductors

3. Fault studies are mainly carried out for:
(A) Designing protection schemes and selecting equipment ratings
(B) Measuring load factor
(C) Improving insulation resistance
(D) Calculating voltage regulation

4. The most common fault in a three-phase power system is:
(A) Line-to-line fault
(B) Three-phase fault
(C) Single line-to-ground fault
(D) Double line-to-ground fault

5. A three-phase fault is also known as a:
(A) Balanced fault
(B) Unbalanced fault
(C) Open-circuit fault
(D) Grounded fault

6. Unbalanced faults include:
(A) Single line-to-ground, line-to-line, and double line-to-ground
(B) Three-phase faults only
(C) Open circuit only
(D) Voltage dips only

7. The magnitude of fault current depends primarily on:
(A) System impedance to the fault point
(B) Load demand
(C) Frequency of operation
(D) Power factor

8. The most severe type of fault in a system is:
(A) Three-phase fault
(B) Line-to-line fault
(C) Single line-to-ground fault
(D) Double line-to-ground fault

9. Short-circuit studies are performed to determine:
(A) Circuit breaker ratings and relay settings
(B) Transformer efficiency
(C) Load variation
(D) Line regulation

10. The unbalanced fault analysis is carried out using:
(A) Symmetrical components method
(B) Kirchhoff’s current law only
(C) Per-phase equivalent circuits
(D) Load flow equations

11. Positive sequence components represent:
(A) Balanced system operation
(B) Faulted phase
(C) Ground current
(D) Open-circuit condition

12. Negative sequence components appear when:
(A) The system is unbalanced
(B) The load is purely resistive
(C) Frequency is high
(D) Voltage is constant

13. Zero sequence components are present only if:
(A) A neutral or ground path exists
(B) The system is balanced
(C) There is no fault
(D) Load is delta-connected

14. The initial current immediately after a fault is known as:
(A) Subtransient current
(B) Steady-state current
(C) Load current
(D) Rated current

15. The DC offset in fault current:
(A) Decays exponentially with time
(B) Increases steadily
(C) Remains constant
(D) Has no effect on system operation

16. The circuit breaker must interrupt:
(A) Maximum fault current safely
(B) Normal load current
(C) Only steady-state current
(D) Excitation current

17. The breaking capacity of a circuit breaker is expressed in:
(A) MVA
(B) kWh
(C) Amperes only
(D) Ohms

18. The transient reactance of a generator affects:
(A) Fault current magnitude
(B) Voltage regulation
(C) Frequency response
(D) Power factor

19. Fault current is usually maximum at:
(A) Generator terminals
(B) End of transmission line
(C) Substation bus
(D) Load end

20. Fault studies help ensure that:
(A) Protective devices operate correctly under fault conditions
(B) Voltage remains constant under load
(C) System frequency is controlled
(D) Efficiency is maximized

21. The transient stability of a system is affected by:
(A) Magnitude and duration of fault
(B) Load factor
(C) Frequency control
(D) System losses

22. In a double line-to-ground fault, which sequence networks are connected?
(A) Positive, negative, and zero in parallel
(B) Positive and negative in series
(C) Positive only
(D) Negative only

23. A balanced fault results in:
(A) Equal fault currents in all phases
(B) Unequal fault voltages
(C) Zero current in one phase
(D) No current flow

24. The per-unit system simplifies fault analysis because:
(A) All quantities are normalized
(B) It eliminates the need for complex phasors
(C) It converts unbalanced systems into DC circuits
(D) It reduces impedance values

25. The symmetrical fault analysis is used for:
(A) Balanced three-phase short circuits
(B) Line-to-line faults only
(C) Unbalanced operation
(D) Open circuit faults

26. Fault current decreases when:
(A) System impedance increases
(B) Voltage increases
(C) Line length decreases
(D) Generator capacity increases

27. A major consequence of fault current is:
(A) Equipment damage due to high thermal and mechanical stress
(B) Improved voltage regulation
(C) Better efficiency
(D) Reduced line losses

28. System performance after a fault depends on:
(A) Fault clearing time and system damping
(B) Load frequency
(C) Line capacitance only
(D) Bus voltage ratings

29. After a fault is cleared, the system stability depends on:
(A) How quickly synchronism is restored
(B) The voltage drop magnitude
(C) Load resistance
(D) Frequency deviation alone

30. Fault studies and performance analysis are essential for:
(A) Ensuring safety, reliability, and protection coordination
(B) Determining load curves
(C) Designing economic tariffs
(D) Improving insulation thickness