Relay And Circuit Breakers MCQ Questions|EEE Made Easy

Contents

RELAY AND CIRCUIT BREAKERS MCQ

1.What is the purpose of back up protection?

A. To increase the speed B. To increase the reach C. To leave no blind spot D. To guard against failure of primary

2.What is the actuating quantity for the relays?

A. Magnitude B. Frequency C. Phase angle D. All of these

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3.Which component ensures the safety of the line from damage

A. Relay B. Circuit breaker C. Bus bar D. Current transformer

4.The tripping circuit is__________

A. AC B. DC C. Either AC or DC D. None of these

5.An impedance relay is used for

A. Earth faults B. Inter phase faults C. Both (A) and (B) D. None of these

6.Relay gets its operating energy from

A. Transformer B. Alternator C. Overhead lines D. C.T., P.T.

7.Percentage differential protection is used to prevent against

A. Inter-turn faults B. Heavy Loads C. External Faults D. Magnetizing current

8.Back up protection is needed for

A. Over voltage B. Short circuits C. Over current D. All of these

9.An instantaneous relay is

A. Permanent moving magnet B. Induction cup C. Shaded pole D. Moving coil

10.Relays for transmission line protection are

A. In three zones B. In two zones C. Independent of zone D. None of these

11.Induction cup relays responds to

A. Current B. Power C. Voltage D. Impedance

12.Ionization in circuit breakers is facilitated by

A. Increase of field strength B. Increase of mean free path C. High temperature D. All of these

13.Arc interruption is done by

A. High resistance interruption B. Low resistance interruption C. Both (A) and (B) D. None of these

14.Part of circuit breaker helpful in breaking the current is

A. Trip Coil B. Contacts C. Handle D. Medium

15.Desired tripping of a circuit breaker is

A. Manually B. Automatically C. That it should give warning D. None of these

16.Arcing time is the time between

A. Separation of circuit breaker and extinction of arc B. Separation of circuit breaker and rise of recovery voltage C. Normal current interruption and arc extinction D. None of these

17.For single frequency transients, ratio of peak restriking voltage to time between voltage zero and peak voltage is called

A. Restriking voltage B. Recovery voltage C. Rate of rise restriking voltage D. Active recovery voltage

18.Time between energization of trip coil and separation of contacts is called

A. Closing time B. Opening time C. Both (A) and (B) D. None of these

19.In circuit breaker, to facilitate arc quenching, dielectric strength can be increased by

A. Lengthening of the gap B. Cooling C. Blast effect D. All of these

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20.Rate of rise restriking voltage depends upon

A. Active recovery voltage B. Natural frequency of oscillations C. Both (A) and (B) D. Rating of circuit breaker

21.An ideal circuit breaker should offer

A. Zero & infinite impedance before & after interruption respectively B. Infinity & zero impedance before & after interruption respectively C. Equal impedance before & after interruption D. None of these

22. Which circuit breaker is installed along with wiring circuit against leakage current protection?
A .OCB B. MCB C. ELCB D. MCCB

23. Which relay hold their contacts in position after power is cutoff?
A .Read relay| B . Current relay | C . Voltage relay | D . Latching relay

24. What is the name of circuit breaker?

A Oil circuit breaker | B Air blast circuit breaker
c. Vacuum circuit breaker | D Air break circuit breaker

25. How the rupturing capacity of circuit breaker is rated?
A KV B KW C MVA D KVAR

26. What is the pick-up voltage in a over voltage relay indicated?
A Working voltage of relay | B Maximum voltage rating of relay |
C Minimum voltage rating of relay | D Minimum voltage to start the relay

27. What is the function of Buchholz relay in power transformer?

A Over load and short circuit protection | B Over voltage and earth fault protection |
C Open circuit and earth fault protection | D Open circuit and over voltage protection |

28.In Which of the following device the load is protected by G’ series MCB ?|
A Ovens | B Geysers |
C Air conditioners D General lighting systems |

30. Which circuit breaker is used as a switch and protective device in the domestic wiring circuit?
A Air circuit breaker | B Miniature circuit breaker |
C Moulded case circuit breaker | D Earth Leakage circuit breaker

31. What is the purpose of trip coil used in circuit breakers? |
A Easy operation | B Remote operation
C Accurate operation | D Emergency operation |

32. What is the function of relay to the breaking operation of circuit breaker in control circuit
A Sensing the fault quantities | B Analyzing the condition of breaker |
C Controlling the Speed in case of fault | D Interpreting the fault situation to operate breaker |

33. What is the effect, if the test button is closed permanently in ELCB?

A Circuit trips intermittently | B Circuit functions normally |
C Circuit switch off completely | D Circuit will not trip on leakage |

34. What is the defect in an air circuit breaker, if trips intermittently on loading?
A Incorrect setting of relay B Excessive heat
C Insufficient air pressure | D Line voltage is too high

35. What is the defect in a oil circuit breaker if the oil heats up excessively? |
A Line voltage is too high | B Excessive load
C Poor dielectric strength | D Defective tripping mechanism

36. What is the cause for the defect if phase to ground fault on the transmission line?
A Components failure | B Insulation failure | C Human error | D Fuse failure

ANSWER KEY- RELAY AND CIRCUIT BREAKERS

1- D 2- D 3- A 4- C 5- C 6- D 7- D 8- B 9- A 10- A 11- D 12- D 13- C 14- B 15- B 16- B 17- A 18- C 19- D 20- C 21- A 22- C 23- D 24- B 25- C 26- D 27- A 28- C 29- B 30- B 31- B 32- D 33- C 34- A 35- C 36- B