MCQOPTIONS
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MCQOPTIONS
This section includes 1267 Mcqs, each offering curated multiple-choice questions to sharpen your Embedded Systems knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Where severe synchronising swing occur, the relay employed is |
| A. | Impedance relay |
| B. | Mho relay |
| C. | Reactance relay |
| D. | Induction relay |
| Answer» C. Reactance relay | |
| 2. |
Requirements of protection power station buildings against direct strokes are |
| A. | Interception |
| B. | Conduction |
| C. | . Dissipation |
| D. | All of the above |
| Answer» E. | |
| 3. |
For the protection of power station buildings against direct strokes therequirements 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 | |
| 4. |
The current zero interruption, in oil and air blast circuitbreakers, 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 | |
| 5. |
The most efficient torque producing actuating structure for the induction typerelays 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 | |
| 6. |
Differential relays are used for protection of |
| A. | Feeders |
| B. | Alternators |
| C. | Transformers |
| D. | All of the above |
| Answer» E. | |
| 7. |
Directional over current relays have two exciting coils connected across |
| A. | CT secondaries of two different phases |
| B. | VT secondaries of two different phases |
| C. | CT and VT secondaries of same phases |
| D. | CT and VT secondaries of two different phases |
| Answer» D. CT and VT secondaries of two different phases | |
| 8. |
A three phase, 33 kV oil circuit breaker is rated 1200 A, 2000 MVA, 3s. What isits symmetrical breaking current? |
| A. | 1200 A |
| B. | 3600 A |
| C. | 35 kA |
| D. | 104.8 kA |
| Answer» D. 104.8 kA | |
| 9. |
Which of the following medium is employed for extinction of arc in air circuitbreaker ? |
| A. | Water |
| B. | Oil |
| C. | Air |
| D. | SF6 |
| Answer» D. SF6 | |
| 10. |
Which among these tests are performed to check the nation or internationalstandards? |
| A. | Type test. |
| B. | Production tests. |
| C. | Site checks. |
| D. | All of the above. |
| Answer» B. Production tests. | |
| 11. |
Switching over voltage arc are more hazardous than lighting surges in case of |
| A. | Unbalanced systems |
| B. | Low-voltages |
| C. | 11 KV systems |
| D. | EHV and UHV systems |
| Answer» E. | |
| 12. |
Which type of air is used in air blast circuit breaker? |
| A. | Ionised air |
| B. | Air free from moisture |
| C. | Air should have least CO2 |
| D. | Air must have oil mist. |
| Answer» C. Air should have least CO2 | |
| 13. |
What is / are the main disadvantage / s of using oil as the quenching medium in the circuit breakers? |
| A. | Need periodical replacement. |
| B. | Risk of formation of explosive mixture with air. |
| C. | Possibility of causing fire hazards. |
| D. | All of the above. |
| Answer» E. | |
| 14. |
Why is it difficult to interrupt a capacitive circuit? |
| A. | The current has a leading power factor. |
| B. | The restriking voltage can be high. |
| C. | Current magnitude is very small. |
| D. | Stored energy in the capacitor is very high. |
| Answer» C. Current magnitude is very small. | |
| 15. |
Time graded protection of a radial feeder can be achieved by using |
| A. | Definite time relay |
| B. | Inverse time relay |
| C. | Both definite and inverse time relays |
| D. | None of the above |
| Answer» D. None of the above | |
| 16. |
An impedance is relay is a |
| A. | Voltage restrained over current relay |
| B. | Voltage restrained directional relay |
| C. | Directional restrained over current relay |
| D. | Directional restrained over voltage relay |
| Answer» B. Voltage restrained directional relay | |
| 17. |
For the protection of power station buildings against direct strokes the requirementsare |
| A. | interception |
| B. | interception and conduction |
| C. | interception, conduction and dissipation |
| D. | interception, conduction, dissipation and reflection |
| Answer» D. interception, conduction, dissipation and reflection | |
| 18. |
For the protection of lines against faults involving variable fault resistance, thepreferred relaying scheme is a |
| A. | Plain impedance relay |
| B. | Directional over-current relay |
| C. | Mho relay |
| D. | Reactance relay |
| Answer» E. | |
| 19. |
Differential relays are used for protection of equipments against |
| A. | Internal faults |
| B. | Over current |
| C. | Reverse current |
| D. | Reverse power |
| Answer» B. Over current | |
| 20. |
The least expensive protection for over current in low-voltage system is |
| A. | Rewirable fuse |
| B. | Isolator |
| C. | Circuit breaker |
| D. | Air-break switch |
| Answer» B. Isolator | |
| 21. |
In axial blast type of CB, expansion of air takes place from ______________. |
| A. | High pressure to low pressure. |
| B. | Low pressure to high pressure. |
| C. | Always in high pressure. |
| D. | Always in low pressure. |
| Answer» B. Low pressure to high pressure. | |
| 22. |
In an inverse definite minimum time, electromagnetic type over current relay, theminimum 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 | |
| 23. |
How is the restriking voltage measured? |
| A. | RMS value |
| B. | Peak value |
| C. | Instantaneous value |
| D. | Average value |
| Answer» C. Instantaneous value | |
| 24. |
A fuse wire of circular cross section has a radius of 0.8mm. The wire blows off at a current of 9(A) What will be the radius of the wire that will blow off at a current of 1A? |
| A. | 0.2 mm |
| B. | 0.18 mm |
| C. | 0.28 mm |
| D. | 0.3 mm |
| Answer» C. 0.28 mm | |
| 25. |
Hey switchgear is device used for |
| A. | Interrupting an electrical circuit |
| B. | Switching an electrical circuit |
| C. | Reaching and controlling an electrical circuit |
| D. | Switching, controlling and protecting the electrical circuit and equipment |
| Answer» E. | |
| 26. |
The line insulation is............. the insulation level at the station equipment |
| A. | Less than |
| B. | Same as |
| C. | More than |
| D. | Not directly related with |
| Answer» E. | |
| 27. |
What is the major cause of the failure of the circuit breaker? |
| A. | Trip circuit open |
| B. | Trip latch defective |
| C. | Spring defective |
| D. | All of these |
| Answer» E. | |
| 28. |
What is the arc voltage in a circuit breaker? |
| A. | In phase with the arc current. |
| B. | Lagging the arc current by 90° |
| C. | Leading the arc current by 90° |
| D. | Lagging the arcing current by 180° |
| Answer» B. Lagging the arc current by 90° | |
| 29. |
Both voltage and current signals are required for |
| A. | A plain over current relay |
| B. | A differential relay |
| C. | A directional relay |
| D. | A biased directional relay |
| Answer» D. A biased directional relay | |
| 30. |
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. | |
| 31. |
The operating speed of a relay depends upon the |
| A. | Rate of flux built up |
| B. | Armature core air gap |
| C. | Spring tension |
| D. | All of these |
| Answer» E. | |
| 32. |
The frequency of carrier in the carrier current pilot scheme is in the range of |
| A. | 1 kHz to 10 kHz |
| B. | 10 kHz to 25 kHz |
| C. | 25 kHz to 50 kHz |
| D. | 50 kHz to 500 kHz |
| Answer» E. | |
| 33. |
What is restriking voltage? |
| A. | The transient voltage that appears across the circuit breaker contacts at the instant of arc extinction. |
| B. | The transient voltage that appears across the circuit breaker contacts at the end of arc extinction. |
| C. | Both (a) and (b) |
| D. | None of the above |
| Answer» B. The transient voltage that appears across the circuit breaker contacts at the end of arc extinction. | |
| 34. |
In a static over current relay, inverse time characteristics are obtained by |
| A. | A transistor amplifier |
| B. | An integrating circuit |
| C. | A transistor switch |
| D. | A differentiating circuit |
| Answer» C. A transistor switch | |
| 35. |
The air blast circuit breakers for 400 kV systems are designed to operate in howmuch time? |
| A. | 0.1 s |
| B. | 0.5 s |
| C. | 50 ms |
| D. | 100µs |
| Answer» D. 100µs | |
| 36. |
Why is the resistance switching used in a air blast circuit breaker? |
| A. | Reduce the magnitude of fault current. |
| B. | Control the CB operating time. |
| C. | Damp out the fast transient. |
| D. | Change the fault current power factor. |
| Answer» D. Change the fault current power factor. | |
| 37. |
The frequency of carrier transmitted by microwave pilot is in the range of |
| A. | 1000 kHz to 1500 kHz |
| B. | 2000 kHz to 5000 kHz |
| C. | 900 kHz to 6000 kHz |
| D. | 10000 kHz to 15000 kHz |
| Answer» D. 10000 kHz to 15000 kHz | |
| 38. |
For which of the following protection from negative sequence current is provided? |
| A. | Generators |
| B. | Motors |
| C. | Transmission line |
| D. | Transformers |
| Answer» B. Motors | |
| 39. |
Impedance relay can be used for |
| A. | Phase faults only |
| B. | Earth faults only |
| C. | Both earth and phase faults |
| D. | None of the above |
| Answer» B. Earth faults only | |
| 40. |
What is the most important property which makes the SF6 very efficient medium for circuit breaking? |
| A. | Is non toxic and non inflammable. |
| B. | Has a high dielectric constant. |
| C. | Has a high breakdown strength |
| D. | Is highly electronegative gas |
| Answer» E. | |
| 41. |
Least number of faults are generally reported for |
| A. | Transmission lines |
| B. | Cables |
| C. | Switchgears |
| D. | Transformers |
| Answer» C. Switchgears | |
| 42. |
The short-circuit in any winding of the transformer is the result of |
| A. | Mechanical vibration |
| B. | Insulation failure |
| C. | Loose connection |
| D. | Impulse voltage |
| Answer» E. | |
| 43. |
How many relays are used to detect interphase fault of a three line system? |
| A. | One |
| B. | Two |
| C. | Three |
| D. | Six |
| Answer» D. Six | |
| 44. |
What is the advantage of HRC fuses over Rewirable fuses? |
| A. | High speed operation |
| B. | High rupturing capacity |
| C. | No ageing effect. |
| D. | All of the above. |
| Answer» E. | |
| 45. |
Rate of rise of restriking voltage depend on_____________? |
| A. | Type of circuit breaker. |
| B. | Capacitance of the system. |
| C. | Inductance of the system. |
| D. | Both (b) and (c) |
| Answer» E. | |
| 46. |
What is the breaking capacity of the air blast circuit breaker? |
| A. | 5000 MVA |
| B. | 6000 MVA |
| C. | 7000 MVA |
| D. | 10000 MVA |
| Answer» D. 10000 MVA | |
| 47. |
Minimum working voltage will be least in case of |
| A. | Silver |
| B. | Graphite |
| C. | Carbon |
| D. | Tungsten |
| Answer» B. Graphite | |
| 48. |
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. | |
| 49. |
For ground fault we prefer |
| A. | Plain impedance relay |
| B. | Directional over current relay |
| C. | Mho relay |
| D. | Reactance relay |
| Answer» E. | |
| 50. |
Protective relays can be designed to respond to ___________. |
| A. | Light intensity, impedance |
| B. | Temperature, resistance, reactance |
| C. | Voltage and current |
| D. | All of these |
| Answer» E. | |