MCQOPTIONS
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MCQOPTIONS
This section includes 657 Mcqs, each offering curated multiple-choice questions to sharpen your Testing Subject knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Inverse time current relays are used for the protection of |
| A. | Feeders |
| B. | Transformers |
| C. | Alternators |
| D. | Both A and B |
| Answer» E. | |
| 2. |
To limit current chopping in vacuum circuit breakers, the contact material employed should have the properties of |
| A. | Low conductivity and high vapour pressure. |
| B. | Low conductivity and low vapour pressure. |
| C. | High conductivity and high vapour pressure. |
| D. | High conductivity and low vapour pressure. |
| Answer» B. Low conductivity and low vapour pressure. | |
| 3. |
In distance protection, the relay measures |
| A. | Negative sequence impedance of the light from relay up to the fault point |
| B. | Positive sequence impedance of the line from relay up to the fault point |
| C. | Self impedance of the line from relay up to the fault point |
| D. | Zero sequence impedance of the line from relay up to the fault point |
| Answer» C. Self impedance of the line from relay up to the fault point | |
| 4. |
Which device sends the information to the circuit breaker to interrupt the circuitin case of fault? |
| A. | Switch |
| B. | Relay |
| C. | Circuit breaker itself does this function. |
| D. | Fuse. |
| Answer» C. Circuit breaker itself does this function. | |
| 5. |
Discrimination between main and back up protection is provided by the use ofrelays which are |
| A. | fact |
| B. | sensitive |
| C. | slow |
| D. | none of the above |
| Answer» D. none of the above | |
| 6. |
On transient fault OC and impedance relay |
| A. | Under reaches |
| B. | Over reaches |
| C. | Reach unaffected |
| D. | None of the above |
| Answer» B. Over reaches | |
| 7. |
What is the normal pressure at which the SF6 gas is maintained in the closed position of the breaker? |
| A. | 2 kg / cm2 |
| B. | 2.5 kg /cm2 |
| C. | 2.8 kg / cm2 |
| D. | 3 kg / cm2 |
| Answer» D. 3 kg / cm2 | |
| 8. |
Which of the following is the least expensive protection for overcurrent is lowvoltage system ? |
| A. | Rewireable fuse |
| B. | Isolator |
| C. | Oil circuit breaker |
| D. | Air break circuit breaker |
| Answer» B. Isolator | |
| 9. |
........ Relays is preferred for phase fault on short transmission line |
| A. | Induction type |
| B. | Reactance |
| C. | Impedance |
| D. | None of the above |
| Answer» C. Impedance | |
| 10. |
The main function of under voltage protective device generally employed with amotor starter is to |
| A. | Open the supply circuit on failure of power supply |
| B. | Control the motor voltage |
| C. | Prevent the opening of supply circuit |
| D. | None of the above |
| Answer» B. Control the motor voltage | |
| 11. |
Which relay is used to detect and protect internal fault in a transformer ? |
| A. | Buchholz relay |
| B. | Directional relay |
| C. | Thermal relay |
| D. | Distance relay |
| Answer» B. Directional relay | |
| 12. |
When does the arc interruption in oil circuit breaker take place? |
| A. | Contacts apart. |
| B. | Voltages becomes zero |
| C. | Current goes through zero |
| D. | All of the above |
| Answer» D. All of the above | |
| 13. |
A thermal protection switch provides protection against what? |
| A. | Overload |
| B. | Temperature |
| C. | Short circuit |
| D. | Over voltage |
| Answer» B. Temperature | |
| 14. |
For which among the following the current ratings are not required? |
| A. | Circuit breakers |
| B. | Relays |
| C. | Isolators |
| D. | Load break switch |
| Answer» D. Load break switch | |
| 15. |
In a circuit breaker, the active recovery voltage depends upon which amongthese? |
| A. | Circuit conditions. |
| B. | Power factor. |
| C. | Both (a) and (b) |
| D. | None of the above |
| Answer» D. None of the above | |
| 16. |
For the protection of transformers, harmonic restraint is used to guard against |
| A. | Magnetising inrush current |
| B. | Unbalanced operation |
| C. | Lightning |
| D. | Switching over-voltage |
| Answer» B. Unbalanced operation | |
| 17. |
Pilot-wire protection scheme is the most economical and provides high speedrelaying for |
| A. | Short length of lines upto 15 km |
| B. | Medium length of lives up to 60 km |
| C. | Long length of lines up to 200 km |
| D. | All of the above |
| Answer» B. Medium length of lives up to 60 km | |
| 18. |
Which one of the following relay has the capability of anticipating the possiblemajor fault in a transformer ? |
| A. | Over-current relay |
| B. | Differential relay |
| C. | Buchholz relay |
| D. | Over fluxing relay |
| Answer» D. Over fluxing relay | |
| 19. |
In a biased differential relay the bias is defined as a ratio of |
| A. | Number of turns of restraining and operating coil |
| B. | Operating coil current and restraining coil current |
| C. | Fault current and operating coil current |
| D. | Fault current and restraining coil current |
| Answer» C. Fault current and operating coil current | |
| 20. |
The types of faults that occur in electric motors are |
| A. | Stator |
| B. | Rotor |
| C. | Overload |
| D. | All of the above |
| Answer» E. | |
| 21. |
The making and breaking currents of a 3 phase ac circuit breakers in powersystems are respectively in ________form. |
| A. | rms value, rms value |
| B. | instantaneous value, rms value |
| C. | rms value, instantaneous value |
| D. | instantaneous value, instantaneous value |
| Answer» E. | |
| 22. |
Assertion (A): In comparison to making capacity of a circuit breaker its breakingcapacity is normally higher. Reason (R): The breaking capacity of a CB is expressed as √3 * VI * 10-6 MVA |
| A. | Both A and R are true and R is the correct explanation of A |
| B. | Both A and R are true and R is not the explanation of A |
| C. | A is true but R is false |
| D. | A is false but R is true. |
| Answer» E. | |
| 23. |
To prevent mal operation of differentially connected relay while energising atransformer, the relay restraining coil is biased with |
| A. | Second harmonic current |
| B. | Third harmonic current |
| C. | Fifth harmonic current |
| D. | Seventh harmonic current |
| Answer» B. Third harmonic current | |
| 24. |
Reactance relays are used for phase fault in.......line |
| A. | Short |
| B. | Medium |
| C. | Long |
| D. | All of the above |
| Answer» B. Medium | |
| 25. |
Admittance relay |
| A. | Nondirectional relay |
| B. | Directional relay |
| C. | Differential relay |
| D. | None of the above |
| Answer» C. Differential relay | |
| 26. |
What is the type of air blast in cross blast type CB? |
| A. | The blast of air is along the ar(C) |
| B. | The blast of air cuts across the ar(C) |
| C. | Both (a) and (b) |
| D. | None of the above. |
| Answer» C. Both (a) and (b) | |
| 27. |
Which of the following circuit breakers is used for the railway electrification? |
| A. | Air blast circuit breaker |
| B. | SF6 circuit breaker |
| C. | Bulk oil circuit breaker |
| D. | Minimum oil circuit breaker |
| Answer» B. SF6 circuit breaker | |
| 28. |
Which among these are the main characteristics of a fuse element? |
| A. | Low melting point |
| B. | High conductivity |
| C. | Least deterioration due to oxidation |
| D. | All of the above |
| Answer» E. | |
| 29. |
For the protection of stator winding of an alternate against internal fault involvingground the relay used is a |
| A. | Biased differential relay |
| B. | Directional over-current relay |
| C. | Plain impedance relay |
| D. | Buchholz relay |
| Answer» B. Directional over-current relay | |
| 30. |
What is the making capacity of the circuit breaker? |
| A. | Less than the asymmetrical breaking capacity of the breaker |
| B. | Greater than the asymmetrical breaking capacity of the breaker |
| C. | Equal to the asymmetrical breaking capacity of the breaker |
| D. | Equal to the symmetrical breaking capacity of the breaker |
| Answer» C. Equal to the asymmetrical breaking capacity of the breaker | |
| 31. |
Reactance relay is normally used for protection against |
| A. | Earth fault only |
| B. | Phase fault only |
| C. | Both earth and phase faults |
| D. | None of the above |
| Answer» B. Phase fault only | |
| 32. |
Which is the main relay for protecting up to 90% of the transmission line-length inthe forward direction? |
| A. | Directional over current relay |
| B. | Mho relay |
| C. | Carrier current protective relay |
| D. | Impedance relay |
| Answer» C. Carrier current protective relay | |
| 33. |
Purpose of backup protection is |
| A. | To increase the speed |
| B. | To increase a reach |
| C. | To leave no blind spot |
| D. | To guard against failure of primary |
| Answer» E. | |
| 34. |
Which among these circuit breakers produce the least arc energy? |
| A. | Plain oil |
| B. | Minimum oil |
| C. | Air blast |
| D. | Air break |
| Answer» D. Air break | |
| 35. |
We do not require any protection against prime mover failure in case of |
| A. | Turbo generator sets |
| B. | Hydro generator sets |
| C. | Diesel engine driven alternators |
| D. | Back pressure turbo generators |
| Answer» B. Hydro generator sets | |
| 36. |
In a contactor, interrupting medium may be |
| A. | Air |
| B. | Oil |
| C. | Sf6 gas |
| D. | Any of the above |
| Answer» E. | |
| 37. |
Why is an isolator installed? |
| A. | To isolate one portion of the circuit from another |
| B. | As an substitute for the circuit breaker |
| C. | It used on either sides of the circuit breaker |
| D. | Both (a) and (c) |
| Answer» B. As an substitute for the circuit breaker | |
| 38. |
For the protection of a large squirrel cage induction motor against single phasenormally |
| A. | An over-current relay is used |
| B. | Differential relay is used |
| C. | Directional relay is used |
| D. | Negative sequence current sensitive relay is used |
| Answer» E. | |
| 39. |
The breaking capacity of a three phase circuit breaker is given by |
| A. | Service line voltage * rated symmetrical current in amperes * 10-6 MVA |
| B. | √3 * Service line voltage * rated symmetrical current in amperes * 10-6 MVA |
| C. | 1.1* Service line voltage * rated symmetrical current in amperes * 10-6 MVA |
| D. | √2 * Service line voltage * rated symmetrical current in amperes * 10-6 MVA |
| Answer» C. 1.1* Service line voltage * rated symmetrical current in amperes * 10-6 MVA | |
| 40. |
SF6 is which type of gas? |
| A. | Electro positive |
| B. | Electro negative |
| C. | Both (a) and (b) |
| D. | None of these |
| Answer» D. None of these | |
| 41. |
Recovery voltage is the value of rms voltage that reappears across the poles of acircuit breaker before_______________ |
| A. | Restriking voltage |
| B. | Final arc extinction |
| C. | Rise of voltage |
| D. | All of the above |
| Answer» C. Rise of voltage | |
| 42. |
For a high speed circuit breaker what will the total clearing time? |
| A. | Few minutes. |
| B. | Few seconds. |
| C. | 1 to 2 cycles. |
| D. | 5 to 20 cycles. |
| Answer» D. 5 to 20 cycles. | |
| 43. |
IDMT relays are used to protect the power transformers against |
| A. | External short-circuit |
| B. | Over loads |
| C. | Internal short-circuits |
| D. | Both A and B |
| Answer» E. | |
| 44. |
In a circuit breaker, ionisation is facilitated by_________________. |
| A. | Increase in field strength. |
| B. | Increase in mean free length. |
| C. | High temperature of the surrounding medium. |
| D. | All of the above. |
| Answer» E. | |
| 45. |
A three phase circuit breaker is rated 2000 MVA, 33 kV. What will be its makingcurrent? |
| A. | 35 kA |
| B. | 49 kA |
| C. | 70 kA |
| D. | 89 kA |
| Answer» E. | |
| 46. |
Which of the following devices will receive voltage surge first travelling on thetransmission line ? |
| A. | Lightning arresters |
| B. | Relays |
| C. | Step-down transformer |
| D. | Switchgear |
| Answer» B. Relays | |
| 47. |
A differential relay response to |
| A. | Algebraic difference of two or more similar electrical quantities |
| B. | Phasor difference of two or more similar electrical quantities |
| C. | Algebraic difference between two currents |
| D. | Algebraic difference between two voltages |
| Answer» C. Algebraic difference between two currents | |
| 48. |
In a balanced voltage pilot wire protection scheme if the pilot circuit gets opened,the relay will |
| A. | Fail to trip on internal faults |
| B. | Trip on full load |
| C. | Trip instantaneously on external faults |
| D. | None of the above |
| Answer» B. Trip on full load | |
| 49. |
Keeping in view the cost and the overall effectiveness, which of the following circuit breaker is best suited for capacitor bank switching? |
| A. | Vacuum circuit breaker |
| B. | Air blast CB |
| C. | SF6 |
| D. | Oil CB |
| Answer» B. Air blast CB | |
| 50. |
The contacts of high voltage switches used in power system are submerged in oil.The main purpose of the oil is to |
| A. | lubricate the contacts |
| B. | insulate the contacts from switch body |
| C. | extinguish the arc |
| D. | all of the above |
| Answer» D. all of the above | |