MCQOPTIONS
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MCQOPTIONS
This section includes 49 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Which of the following medium is employed for extinction of arc in air circuit breaker ? |
| A. | Water |
| B. | Oil |
| C. | Air |
| D. | SF6 |
| Answer» D. SF6 | |
| 2. |
The air blast circuit breakers for 400 kV systems are designed to operate in how much time? |
| A. | 0.1 s |
| B. | 0.5 s |
| C. | 50 ms |
| D. | 100 s |
| Answer» D. 100 s | |
| 3. |
When using air blast circuit breaker, current chopping is a phenomenon observed when |
| A. | A long overhead line is switched off. |
| B. | A bank of capacitors is switched off. |
| C. | A transformer on no load is switched off. |
| D. | A heavy load is switched off. |
| Answer» D. A heavy load is switched off. | |
| 4. |
Which among these is the least expensive protection for over current in low voltage system? |
| A. | Rewirable fuse. |
| B. | Isolator. |
| C. | Circuit breaker. |
| D. | Air breaker switch. |
| Answer» B. Isolator. | |
| 5. |
Recovery voltage is the value of rms voltage that reappears across the poles of a circuit breaker before_______________ |
| A. | Restriking voltage |
| B. | Final arc extinction |
| C. | Rise of voltage |
| D. | All of the above |
| Answer» C. Rise of voltage | |
| 6. |
In a circuit breaker, the active recovery voltage depends upon which among these? |
| A. | Circuit conditions. |
| B. | Power factor. |
| C. | Both (a) and (b) |
| D. | None of the above |
| Answer» D. None of the above | |
| 7. |
The interrupting time of a circuit breaker is the period between the instant of _________. |
| A. | Initiation of short circuit and the arc extinction on an opening operation. |
| B. | Energizing the trip circuit and the arc extension on an opening operation. |
| C. | Initiation of short circuit and the parting of primary arc contacts. |
| D. | Energizing of the trip circuit and the parting of primary arc contacts. |
| Answer» C. Initiation of short circuit and the parting of primary arc contacts. | |
| 8. |
Discrimination between main and back up protection is provided by the use of relays which are |
| A. | fact |
| B. | sensitive |
| C. | slow |
| D. | none of the above |
| Answer» D. none of the above | |
| 9. |
Which of the following devices will receive voltage surge first travelling on the transmission line ? |
| A. | Lightning arresters |
| B. | Relays |
| C. | Step-down transformer |
| D. | Switchgear |
| Answer» B. Relays | |
| 10. |
A three phase, 33 kV oil circuit breaker is rated 1200 A, 2000 MVA, 3s. What is its symmetrical breaking current? |
| A. | 1200 A |
| B. | 3600 A |
| C. | 35 kA |
| D. | 104.8 kA |
| Answer» D. 104.8 kA | |
| 11. |
The making and breaking currents of a 3 phase ac circuit breakers in power systems 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. | |
| 12. |
Assertion (A): In comparison to making capacity of a circuit breaker its breaking capacity 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. | |
| 13. |
Which circuit breaker is preferred to be installed in extra high voltage AC system? |
| A. | Bulk oil type circuit breaker |
| B. | Air blast circuit breaker |
| C. | SF6 circuit breaker |
| D. | Vacuum circuit breaker |
| Answer» D. Vacuum circuit breaker | |
| 14. |
Which among these tests are performed to check the nation or international standards? |
| A. | Type test. |
| B. | Production tests. |
| C. | Site checks. |
| D. | All of the above. |
| Answer» B. Production tests. | |
| 15. |
A three phase circuit breaker is rated 2000 MVA, 33 kV. What will be its making current? |
| A. | 35 kA |
| B. | 49 kA |
| C. | 70 kA |
| D. | 89 kA |
| Answer» E. | |
| 16. |
The most efficient torque producing actuating structure for the induction type relays is |
| A. | Shaded pole structure |
| B. | Watt hour meter structure |
| C. | Induction cup structure |
| D. | Single induction loop structure |
| Answer» D. Single induction loop structure | |
| 17. |
Which device sends the information to the circuit breaker to interrupt the circuit in case of fault? |
| A. | Switch |
| B. | Relay |
| C. | Circuit breaker itself does this function. |
| D. | Fuse. |
| Answer» C. Circuit breaker itself does this function. | |
| 18. |
The inductive interference between power and communication line can be minimized by |
| A. | transposition of the power line |
| B. | transposition of the communication line |
| C. | both (A) and (B) |
| D. | increasing the distance between the conductors |
| Answer» D. increasing the distance between the conductors | |
| 19. |
For the protection of lines against faults involving variable fault resistance, the preferred relaying scheme is a |
| A. | Plain impedance relay |
| B. | Directional over-current relay |
| C. | Mho relay |
| D. | Reactance relay |
| Answer» E. | |
| 20. |
For the protection of stator winding of an alternate against internal fault involving ground 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 | |
| 21. |
The domains of power system where directional over current relay is indispensable are |
| A. | In case of parallel feeder protection |
| B. | In case of ring main feeder protection |
| C. | Both A and B |
| D. | None of the above |
| Answer» D. None of the above | |
| 22. |
To prevent mal operation of differentially connected relay while energising a transformer, 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 | |
| 23. |
The inverse definite mean time relays are used for over current and earth fault protection of transformer against |
| A. | Heavy loads |
| B. | Internal short circuits |
| C. | External short circuits |
| D. | All of the above |
| Answer» C. External short circuits | |
| 24. |
In an inverse definite minimum time, electromagnetic type over current relay, the minimum time feature is achieved because of |
| A. | Saturation of the magnetic circuit |
| B. | Proper mechanical design |
| C. | Appropriate time delay element |
| D. | Electromagnetic damping |
| Answer» B. Proper mechanical design | |
| 25. |
In order that current should flow without causing excessive heating or voltage drop, the relay contacts should |
| A. | Have low contact resistance |
| B. | Be clean and smooth |
| C. | Be of sufficient size and proper shape |
| D. | Have all above properties |
| Answer» E. | |
| 26. |
For which of the following ratings of the transformer differential protection is recommended? |
| A. | Above 30 KVA |
| B. | Equal to and above 5 MVA |
| C. | Equal two and above 25 MVA |
| D. | None of the above |
| Answer» C. Equal two and above 25 MVA | |
| 27. |
The protection against direct lighting strokes and a high-voltage steep waves is provided by |
| A. | Ground wires |
| B. | Lightning arresters |
| C. | Lightning arresters and ground wires |
| D. | Earthing of neutral |
| Answer» D. Earthing of neutral | |
| 28. |
In a HRC fuse what is the time between the cut off and the final current zero called? |
| A. | Pre - arcing time. |
| B. | Arcing time. |
| C. | Total operating time. |
| D. | None of these. |
| Answer» C. Total operating time. | |
| 29. |
Which of the following is the least expensive protection for overcurrent is low voltage system ? |
| A. | Rewireable fuse |
| B. | Isolator |
| C. | Oil circuit breaker |
| D. | Air break circuit breaker |
| Answer» B. Isolator | |
| 30. |
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 | |
| 31. |
The heat produced at the contact point owing to flow of electric current is least affected by_____________________. |
| A. | Temperature of the surrounding medium. |
| B. | Contact resistance. |
| C. | Magnitude of electric current flowing. |
| D. | Duration of flow of current. |
| Answer» B. Contact resistance. | |
| 32. |
For the protection of power station buildings against direct strokes the requirements are |
| A. | interception |
| B. | interception and conduction |
| C. | interception, conduction and dissipation |
| D. | interception, conduction, dissipation and reflection |
| Answer» D. interception, conduction, dissipation and reflection | |
| 33. |
In between the generating station and consumers a number of transformation and switching stations exist, these are called the |
| A. | Switchgears |
| B. | Substations |
| C. | Intermediate substations |
| D. | Transformation stations |
| Answer» C. Intermediate substations | |
| 34. |
For the protection of power station buildings against direct strokes the requirements are |
| A. | Interception |
| B. | Interception and conduction |
| C. | Interception, conduction and dissipation |
| D. | Interception,conduction,dissipation and reflection |
| Answer» D. Interception,conduction,dissipation and reflection | |
| 35. |
To protect most of the electrical equipment handling low power, the types of relays used are |
| A. | Thermocouple |
| B. | Electronic and bimetallic |
| C. | Both A and B |
| D. | None of the above |
| Answer» D. None of the above | |
| 36. |
For the protection of a large squirrel cage induction motor against single phase normally |
| 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. | |
| 37. |
Which one of the following relay has the capability of anticipating the possible major fault in a transformer ? |
| A. | Over-current relay |
| B. | Differential relay |
| C. | Buchholz relay |
| D. | Over fluxing relay |
| Answer» D. Over fluxing relay | |
| 38. |
The voltage appearing across the contacts after opening of the circuit breaker is called______voltage. |
| A. | recovery |
| B. | surge |
| C. | operating |
| D. | arc |
| Answer» B. surge | |
| 39. |
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 | |
| 40. |
By using low resistance method for arc extension what is the value of arc resistance? |
| A. | Arc resistance is zero. |
| B. | Arc resistance is high |
| C. | Arc resistance is low |
| D. | Arc resistance is very high |
| Answer» D. Arc resistance is very high | |
| 41. |
The transient voltages that appears across the contacts at the instant of arc extinction is called ..............voltage |
| A. | Supply |
| B. | Recovery |
| C. | Restriking |
| D. | Peak |
| Answer» D. Peak | |
| 42. |
Which is the main relay for protecting up to 90% of the transmission line-length in the forward direction? |
| A. | Directional over current relay |
| B. | Mho relay |
| C. | Carrier current protective relay |
| D. | Impedance relay |
| Answer» C. Carrier current protective relay | |
| 43. |
The operating characteristics of the reactance relay in the complex impedance plane is a |
| A. | Circle with its origin at the centre of the R-X plane |
| B. | Circle passing through the origin |
| C. | Straight line passing through the origin |
| D. | Straight line parallel to the X axis |
| Answer» E. | |
| 44. |
In order that current should flow without causing excessive heating or voltage drop, the relay contacts should |
| A. | have low contact resistance |
| B. | be clean and smooth |
| C. | be of sufficient size and proper shape |
| D. | have all above properties |
| Answer» E. | |
| 45. |
Pilot-wire protection scheme is the most economical and provides high speed relaying 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 | |
| 46. |
The main function of under voltage protective device generally employed with a motor 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 | |
| 47. |
Which of the following circuit breakers has high reliability and minimum maintenance ? |
| A. | Air blast circuit breakers |
| B. | Circuit breaker with SF6 gas |
| C. | Vacuum circuit breakers |
| D. | Oil circuit breakers |
| Answer» C. Vacuum circuit breakers | |
| 48. |
The current zero interruption, in oil and air blast circuit breakers, is achieved by |
| A. | lengthening of the gap |
| B. | cooling and blast effect |
| C. | both (A) and (B) |
| D. | deionizing the oil with forced air |
| Answer» D. deionizing the oil with forced air | |
| 49. |
A differential relay measures the vector difference between |
| A. | two currents |
| B. | two voltages |
| C. | two or more similar electrical quantities |
| D. | none of the above |
| Answer» D. none of the above | |