Principles of Protection — MCQs – EE

1. The main purpose of protection in a power system is to:
(A) Improve generation efficiency
(B) Detect and isolate faulty equipment
(C) Reduce power factor losses
(D) Control system frequency

2. A protection system must operate:
(A) Fast, selective, and reliable
(B) Slowly and deliberately
(C) Randomly depending on the load
(D) Only during maintenance

3. The fundamental principle of protection is based on:
(A) Abnormal conditions causing measurable electrical changes
(B) Load balancing
(C) Energy storage
(D) Voltage step-up operation

4. Selectivity in protection ensures that:
(A) Only the faulty section is disconnected
(B) The whole system is shut down
(C) Faults are ignored
(D) All relays operate together

5. Reliability of protection means:
(A) It always operates correctly when required
(B) It operates randomly
(C) It depends on temperature
(D) It needs frequent manual reset

6. Sensitivity in a protection system refers to:
(A) The ability to detect even small abnormal conditions
(B) The ability to withstand faults
(C) The relay’s mechanical strength
(D) The insulation level

7. Speed of operation in protection is important to:
(A) Limit equipment damage and maintain stability
(B) Increase system voltage
(C) Improve efficiency
(D) Increase transmission losses

8. The main components of a protection system are:
(A) Sensing devices, relays, and circuit breakers
(B) Transformers and generators
(C) Transmission lines and loads
(D) Voltage regulators and rectifiers

9. Zone of protection is defined as:
(A) The part of the system protected by a given scheme
(B) The area covered by a generator
(C) The total system voltage
(D) The transmission distance

10. Backup protection operates:
(A) When the primary protection fails
(B) Before primary protection
(C) Simultaneously with primary protection
(D) Only under normal conditions

11. Primary protection is designed to:
(A) Isolate the fault immediately at its location
(B) Support backup relays
(C) Regulate voltage
(D) Control frequency

12. Redundancy in protection means:
(A) Having additional backup systems to improve reliability
(B) Disconnecting spare equipment
(C) Reducing relay count
(D) Installing larger circuit breakers

13. Grading of protection ensures:
(A) Proper time coordination between relays
(B) Equal current distribution
(C) Constant voltage across the system
(D) Uniform power flow

14. A protection relay operates when:
(A) The monitored quantity exceeds its threshold
(B) Load is balanced
(C) Voltage remains constant
(D) System is stable

15. Protection systems must be designed to:
(A) Avoid unnecessary tripping during transient conditions
(B) Disconnect all loads during voltage drop
(C) Operate continuously under any fluctuation
(D) Respond to every minor disturbance

16. Economy in protection refers to:
(A) Achieving adequate protection at minimum cost
(B) Using the most expensive equipment
(C) Avoiding maintenance costs
(D) Eliminating all relays

17. The dependability of a protection system refers to:
(A) Probability that it will operate correctly during a fault
(B) Cost effectiveness
(C) Maintenance schedule
(D) Frequency regulation capability

18. A relay that operates based on the ratio of two electrical quantities is called:
(A) Differential relay
(B) Overcurrent relay
(C) Distance relay
(D) Thermal relay

19. Stability of the protection system means:
(A) It should not operate for external faults
(B) It must always trip during minor surges
(C) It should trip for all disturbances
(D) It must depend on system load

20. The basic requirement of protective relaying is:
(A) Selectivity, reliability, and speed
(B) High impedance
(C) Voltage control
(D) Load management

21. Protection zones are usually made to:
(A) Overlap slightly to avoid unprotected regions
(B) Have large gaps between them
(C) Be completely isolated
(D) Depend on system voltage

22. Coordination between protection devices ensures:
(A) Sequential isolation of faulted parts
(B) Simultaneous tripping of all breakers
(C) Random tripping of relays
(D) Equal voltage at all buses

23. Discrimination in protection refers to:
(A) The ability to distinguish between fault and normal conditions
(B) The speed of circuit breaker operation
(C) The magnitude of current
(D) The size of protection zone

24. A good protection system should:
(A) Operate only when required and remain stable otherwise
(B) Operate for all transient fluctuations
(C) Depend solely on manual operation
(D) Trip the system frequently

25. A typical protective scheme includes:
(A) CTs, PTs, relays, and circuit breakers
(B) Transformers, reactors, and loads
(C) Motors, cables, and switches
(D) Resistors and capacitors

26. A fault current is characterized by:
(A) A sudden rise in current due to abnormal condition
(B) A steady current under normal load
(C) A decrease in voltage and current
(D) Zero current flow

27. Backup protection is generally located:
(A) Away from the primary protected section
(B) Inside the main relay housing
(C) Near the load center
(D) At the generating station only

28. The reliability of a protection system improves by:
(A) Using redundant relays and breakers
(B) Reducing circuit breakers
(C) Increasing fault duration
(D) Ignoring small faults

29. The relay operating characteristic depends mainly on:
(A) The type of protection scheme and fault condition
(B) The type of transformer
(C) The power factor
(D) The size of generator

30. The ultimate goal of a protection system is to:
(A) Maintain system stability and minimize equipment damage
(B) Increase load current
(C) Improve frequency
(D) Enhance insulation levels