Multiple Choice Question (MCQ) of Protective Relays

Multiple Choice Question (MCQ) of Protective Relays

1. A single phasing relay can be used with

1ɸ motor
2 ɸ motor
3 ɸ motor
All of these

2. A relay is used to

Break the fault current
Sense the fault
Sense the fault and direct to trip the circuit breaker
All of these

3. In impedance relay, current element torque should be

Equal to voltage element torque
Greater than voltage element torque
Less than voltage element torque
None of these

4. Over current fault is most likely in

Overhead line equipment

5. Distance relays are generally

Impedance type
MHO type
Reactance type
All of these

6. Instantaneous relay should operate within

0.0001 sec
0.001 sec
0.01 sec
0.1 sec

7. In an impedance relay, fault current is maximum if fault occurs near the

Center of the line
None of these

8. Relays for transmission line protection are

In three zones
In two zones
Independent of zone
None of these

9. Time classification of relays includes

Instantaneous relays
Definite time lag
Inverse time lag
All of these

10. Directional relays responds to


11. For phase fault on long line, which relay is used?

MHO relays
Reactance relays
Impedance relays
All of these

12. Under voltage relays are used for

Bus bars
All of these

13. An impedance relay is used for

Earth faults
Interphase faults
Both (a) and (b)
None of these

14. Over voltage may be due to

Lightning impulse waveform
50 Hz a.c.
Peak value of 50 Hz a.c.
All of these

15. In oil circuit breakers, dielectric strength of oil should be

None of these

16. Negative Phase sequence relay is used to protect ……. from phase to phase faults

Bus bar
Electric Heater

17. Distance relay operates on ………………….

Magnitude of voltage
Magnitude of current
Ratio of voltage and current
Magnitude of reactive power

18. A protective relay …………..

detects the fault location
interrupts the fault current
eparates the electrical circuit in case of faul
operates same as electrical fuse

19. Buchholz relays are used to protect ………………

Electrical Transformer
Electrical Generator
Electrical Bus Bar
Electrical Motor

20. Earth fault protection is provided by employing an Over current relay between phase and earth: