1. A relay is a device used to:
(A) Detect abnormal conditions and initiate circuit breaker operation
(B) Generate power
(C) Regulate frequency
(D) Reduce system losses
2. Electromagnetic relays operate based on:
(A) Electromagnetic induction or attraction
(B) Mechanical pressure
(C) Thermal expansion
(D) Light intensity
3. The main components of an electromagnetic relay are:
(A) Coil, armature, contacts, and spring
(B) Resistors and capacitors
(C) Diodes and transistors
(D) Lamps and switches
4. In an electromagnetic relay, when current flows through the coil:
(A) Magnetic flux attracts the armature to close or open contacts
(B) Temperature rises and opens the circuit
(C) Mechanical pressure increases
(D) Resistance decreases
5. Electromagnetic relays are generally used for:
(A) Simpler, low-speed protection schemes
(B) High-speed and complex logic protection
(C) Digital communication systems
(D) Frequency measurement only
6. Static relays differ from electromagnetic relays in that:
(A) They have no moving parts
(B) They use mechanical motion
(C) They rely on coils and armatures
(D) They consume more power
7. The operating principle of a static relay is based on:
(A) Electronic circuits using transistors, diodes, and amplifiers
(B) Magnetic flux linkage
(C) Thermal conduction
(D) Inductive coupling
8. The main advantage of static relays is:
(A) High speed and reliability
(B) Large size
(C) Frequent maintenance
(D) Mechanical operation
9. Numerical relays are based on:
(A) Microprocessor or microcontroller technology
(B) Electromagnetic attraction
(C) Magnetic circuit design
(D) Analog amplifiers
10. The inputs to numerical relays are usually:
(A) Analog signals converted to digital form
(B) DC power directly
(C) Mechanical forces
(D) Optical pulses
11. Electromagnetic relays are generally:
(A) Slower in operation compared to static or numerical relays
(B) Faster than static relays
(C) More compact
(D) Less affected by mechanical wear
12. A major drawback of electromagnetic relays is:
(A) Mechanical wear and tear due to moving parts
(B) High electronic noise
(C) Inability to handle DC circuits
(D) High insulation requirements
13. Static relays have better performance because:
(A) They use solid-state components
(B) They have rotating parts
(C) They depend on magnetic field intensity
(D) They use thermal expansion
14. Numerical relays can perform:
(A) Multiple protection functions with one device
(B) Only one type of protection
(C) Voltage regulation only
(D) Frequency measurement only
15. Self-diagnosis and event recording are features of:
(A) Numerical relays
(B) Electromagnetic relays
(C) Static relays
(D) Thermal relays
16. Static relays consume:
(A) Less power compared to electromagnetic relays
(B) More power
(C) The same power
(D) Variable power depending on load
17. The time of operation for a numerical relay is generally:
(A) Very short (in milliseconds)
(B) Very long (in seconds)
(C) Adjustable manually only
(D) Dependent on mechanical motion
18. Maintenance requirement of numerical relays is:
(A) Very low due to lack of moving parts
(B) Very high due to frequent calibration
(C) Same as electromagnetic relays
(D) Dependent on temperature
19. Electromagnetic relays are most suitable for:
(A) Simple overcurrent or earth fault protection
(B) Multi-zone digital protection
(C) Wide-area protection control
(D) Remote monitoring systems
20. Static relays provide better:
(A) Sensitivity and accuracy
(B) Mechanical operation
(C) Delay in operation
(D) Thermal overload capacity
21. Numerical relays can communicate with other devices using:
(A) Communication protocols like IEC 61850 or Modbus
(B) Mechanical linkages
(C) Manual switches
(D) Optical mirrors
22. The biggest advantage of numerical relays in modern power systems is:
(A) Integration, flexibility, and remote control
(B) Simple mechanical operation
(C) Heavy construction
(D) Lack of electronic circuits
23. Electromagnetic relays require:
(A) Regular maintenance and testing
(B) No maintenance at all
(C) Microprocessor programming
(D) Battery backup systems
24. In static relays, signal comparison and decision-making are done by:
(A) Analog electronic circuits
(B) Rotating armatures
(C) Mechanical contacts
(D) Springs and levers
25. The cost of numerical relays compared to static relays is generally:
(A) Higher, but with greater functionality
(B) Lower for small systems
(C) The same
(D) Negligible
26. Static relays are preferred over electromagnetic relays because they:
(A) Have faster operation and better accuracy
(B) Are heavier and larger
(C) Require moving parts
(D) Operate only at high voltage
27. Numerical relays can replace multiple discrete relays because:
(A) They are programmable and multifunctional
(B) They use mechanical switches
(C) They have rotating contacts
(D) They rely on armature motion
28. The output of a numerical relay is usually in the form of:
(A) A digital trip signal
(B) A mechanical movement
(C) A magnetic force
(D) A thermal change
29. Electromagnetic relays are gradually being replaced because they:
(A) Are bulky and slow compared to modern relays
(B) Are more reliable
(C) Have better communication ability
(D) Require no power supply
30. The most advanced type of relay used in present-day protection systems is:
(A) Numerical relay
(B) Static relay
(C) Electromagnetic relay
(D) Thermal relay