MCQOPTIONS
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MCQOPTIONS
This section includes 93 Mcqs, each offering curated multiple-choice questions to sharpen your Power Systems knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
An ability of Relay system to operate under predetermined condition is called ________. |
| A. | Sensitivity |
| B. | Selectivity |
| C. | Stability |
| D. | Reliability |
| Answer» B. Selectivity | |
| 2. |
Over speed protection of a generator is done by |
| A. | Governor |
| B. | Differential protection |
| C. | Over current relay |
| D. | Alarm |
| Answer» B. Differential protection | |
| 3. |
In a 3-step distance protection, the reach of the three zones of the relay at the beginning of the first line typically extends into |
| A. | 100% of the first line, 50% of the second line and 20% of the third line |
| B. | 80% of the first line, 50% of the second line and 20% of the third line |
| C. | 80% of the first line, 50% of the second line and 10% of the third line |
| D. | 50% of the first line, 50% of the second line and 20% of the third line |
| Answer» C. 80% of the first line, 50% of the second line and 10% of the third line | |
| 4. |
A good fuse wire must have: |
| A. | High melting point |
| B. | High Ohmic losses |
| C. | High Conductivity |
| D. | High Deterioration |
| Answer» D. High Deterioration | |
| 5. |
Material used for making small rating fuses is |
| A. | aluminum |
| B. | copper |
| C. | silver |
| D. | lead and tin |
| Answer» E. | |
| 6. |
During current chopping the current actually breaks... |
| A. | During the instant of natural current zero |
| B. | Before the instant of natural current zero |
| C. | After the instant of natural current zero |
| D. | Irrespective of the instant of natural zero |
| Answer» C. After the instant of natural current zero | |
| 7. |
Earth breaker circuit uses |
| A. | Polarized Relay |
| B. | Reed Relay |
| C. | Latching Relay |
| D. | Machine Tool Relay |
| Answer» D. Machine Tool Relay | |
| 8. |
Directional relays are based on the flow of |
| A. | Power |
| B. | Voltage wave |
| C. | Current |
| D. | Field |
| Answer» B. Voltage wave | |
| 9. |
A sample power system network is shown in the figure given below. The reactance marked are in P.U. What is the P.U. value of Y22 of Bus Admittance matrix (YBus)? |
| A. | j10.0 |
| B. | j0.4 |
| C. | –j0.1 |
| D. | –j20.0 |
| Answer» E. | |
| 10. |
In digital relay, the ON and OFF state is represented in binary numbers as _____ and _____ respectively. |
| A. | 0, 1 |
| B. | 1, 0 |
| C. | 0, 0 |
| D. | 1, 1 |
| Answer» C. 0, 0 | |
| 11. |
Determine the time of operation of a relay of rating 5 A, 2.2s IDMT and having a relay setting of 125%, TMS = 0.6. It is connected to the supply circuit through a CT 400 : 5 ratio. The fault current is 4000 A.PSM25810Time1083.22.5 |
| A. | 1.89 s |
| B. | 1.87 s |
| C. | 1.93 s |
| D. | 1.92 s |
| Answer» E. | |
| 12. |
For rural electrification in India, which circuit breaker is generally used? |
| A. | Oil |
| B. | SF6 |
| C. | Vacuum |
| D. | Air blast |
| Answer» D. Air blast | |
| 13. |
Consider the following statements:HRC fuse as compared to rewirable fuse has:(A) no aging effect(B) high speed of operation(C) high rupturing capacity |
| A. | Only A and B |
| B. | Only B |
| C. | Only B and C |
| D. | All three |
| Answer» E. | |
| 14. |
Inverted operation of a generator can be protected using ______. |
| A. | Over frequency relay |
| B. | Over speed relay |
| C. | Reverse power relay |
| D. | Overload relay |
| Answer» D. Overload relay | |
| 15. |
Over conventional electromechanical relays, the static relays have the advantages of |
| A. | low power consumption, less maintenance and greater sensitivity |
| B. | compact size and quick operation |
| C. | wide range of characteristics approaching more or less to ideal requirement |
| D. | All of the above |
| Answer» E. | |
| 16. |
A 10 kV alternator is protected by the balanced circulating current system. It is grounded through a 10 Ω resistance. The protective relay operates at 1.8 A in the pilot wires, which are connected to the secondary windings of 1000/5 CT. The percentage winding which remains unprotected will be |
| A. | 20% |
| B. | 31% |
| C. | 62% |
| D. | 76% |
| Answer» D. 76% | |
| 17. |
In transformers, Buchholz relay is used for detecting: |
| A. | internal faults |
| B. | external faults |
| C. | insulation failure |
| D. | overcurrent |
| Answer» B. external faults | |
| 18. |
For earth fault, the preferred relay is |
| A. | overcurrent relay |
| B. | impedance relay |
| C. | directional relay |
| D. | reactance relay |
| Answer» E. | |
| 19. |
________ is not a method of high resistance interruption of arc extinction: |
| A. | Blast effect |
| B. | Arc lengthening |
| C. | Arc constraining |
| D. | Arc cooling |
| Answer» B. Arc lengthening | |
| 20. |
Magnitude relay is also called _____ . |
| A. | Thermal Relay |
| B. | Hybrid Relay |
| C. | Induction Relay |
| D. | Reed Relay |
| Answer» D. Reed Relay | |
| 21. |
Plug setting of an electromagnetic relay can be altered by varying |
| A. | Number of ampere turns |
| B. | Air gap of magnetic path |
| C. | Adjustable back stop |
| D. | None of these |
| Answer» B. Air gap of magnetic path | |
| 22. |
For the protection of a very long extra high voltage line, the protective relay used is: |
| A. | Over current with extremely inverse characteristics |
| B. | Percentage differential relay |
| C. | Reactance type distance relay |
| D. | Mho type distance relay |
| Answer» E. | |
| 23. |
Buchholz relay is used to protect |
| A. | Transmission line |
| B. | Generator |
| C. | Transformer |
| D. | Motor |
| Answer» D. Motor | |
| 24. |
Induction relays are used with: |
| A. | d.c. quantities |
| B. | a.c. quantities |
| C. | d.c. and a.c. both |
| D. | None of these |
| Answer» C. d.c. and a.c. both | |
| 25. |
ELCB is a |
| A. | Safety device |
| B. | Current controlling device |
| C. | Voltage controlling device |
| D. | Both 2 and 3 |
| Answer» B. Current controlling device | |
| 26. |
Power stations and sub-stations are protected against direct strokes of lightning using: |
| A. | Rod gap arrester |
| B. | Overhead ground wires |
| C. | Earthing screen |
| D. | Horn gap arrester |
| Answer» D. Horn gap arrester | |
| 27. |
Programmable Logical Controllers are the devices that were invented basically to replace |
| A. | Switches |
| B. | Circuit Breakers |
| C. | Relays |
| D. | None of the above |
| Answer» D. None of the above | |
| 28. |
An over current relay of current rating 5 A and setting 150% is connected to the secondary of CT of ratio 300:5. Then the current in the lines for which the relay pick up is |
| A. | 300 A |
| B. | 450 A |
| C. | 150 A |
| D. | 200 A |
| Answer» C. 150 A | |
| 29. |
Earthing is necessary to give protection against |
| A. | Danger of electric shock |
| B. | Voltage fluctuation |
| C. | Overloading |
| D. | High temperature of conductor |
| Answer» B. Voltage fluctuation | |
| 30. |
A fuse is never inserted in: |
| A. | Neutral wire |
| B. | Negative of DC circuit |
| C. | Positive of DC circuit |
| D. | Phase line |
| Answer» B. Negative of DC circuit | |
| 31. |
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 |
| Answer» E. | |
| 32. |
A Buchholz relay is used for |
| A. | protection of transformer against all internal faults. |
| B. | protection of transformer against all external faults. |
| C. | protection of transformer against both internal and external faults. |
| D. | protection of induction motors |
| Answer» B. protection of transformer against all external faults. | |
| 33. |
Making capacity of a circuit breaker is equal to |
| A. | 2.55 times symmetrical breaking capacity |
| B. | 1.5 times symmetrical breaking capacity |
| C. | √2 times symmetrical breaking capacity |
| D. | Symmetrical breaking capacity |
| Answer» B. 1.5 times symmetrical breaking capacity | |
| 34. |
Buccholz relay is essential for protection against transformer’s ______. |
| A. | inner-turn fault |
| B. | HT and LT fault |
| C. | earth-fault |
| D. | series fault |
| Answer» B. HT and LT fault | |
| 35. |
In thyrite lightning arrester, on doubling the voltage the current increases to ______. |
| A. | 4 times |
| B. | 12.6 times |
| C. | 2 times |
| D. | 6.6 times |
| Answer» C. 2 times | |
| 36. |
Phase modifier is normally installed in the case of |
| A. | short transmission lines |
| B. | medium length lines |
| C. | long length lines |
| D. | all length lines |
| Answer» D. all length lines | |
| 37. |
A reactance relay is also known as: |
| A. | Directional restrained overcurrent relay |
| B. | Directional restrained directional relay |
| C. | Voltage restrained directional relay |
| D. | Voltage restrained overcurrent relay |
| Answer» B. Directional restrained directional relay | |
| 38. |
Earthing transformer is used to |
| A. | Improve neutral wire’s current capacity |
| B. | Avoid overheating of transformer |
| C. | Provide artificial earthing |
| D. | Avoid harmonics |
| Answer» D. Avoid harmonics | |
| 39. |
Lightning arrestor is consists of: |
| A. | A spark gap in parallel with non-linear resistor |
| B. | A spark gap in parallel with linear resistor |
| C. | A spark gap in series with non-linear resistor |
| D. | A spark gap in series with linear resistor |
| Answer» D. A spark gap in series with linear resistor | |
| 40. |
In busbar protection, what is the method of providing an earthed metal barrier surrounding a bus bar throughout its length called? |
| A. | Distance protection |
| B. | Time graded over current protection |
| C. | Fault bus protection |
| D. | Differential protection |
| Answer» D. Differential protection | |
| 41. |
Back up protection is generally employed for protection against: |
| A. | Open circuit faults |
| B. | Earth fault |
| C. | Short circuit fault |
| D. | All of these |
| Answer» E. | |
| 42. |
In Rod Gap Arrester, a current limiting resistance is connected in series with the rod in order to ______. |
| A. | Increase the rod gap |
| B. | Avoid cascading of steep fronted waves |
| C. | Avoid continued sparking even at low voltage |
| D. | Reduce breakdown voltage |
| Answer» D. Reduce breakdown voltage | |
| 43. |
In oil and air blast circuit breakers, the current zero interruption is attained by |
| A. | Increase the length of the contact gap |
| B. | cooling and blast effect |
| C. | deionizing the oil with forced air |
| D. | both (a) and (b) |
| Answer» E. | |
| 44. |
In the case of circuit breakers if the length of arc increases, its resistance: |
| A. | decreases |
| B. | increases |
| C. | remain same |
| D. | sometimes increases or decreases |
| Answer» C. remain same | |
| 45. |
A 3-phase transformer rated for 33/6.6 kV is connected to a star/delta and the current transfer on the LV side has a ratio of 500 : 5. Determine the ratio of the current transformer on the HV side. |
| A. | 100 : 5 |
| B. | \(110:\frac{5}{{\sqrt 3 }}\) |
| C. | \(100:\frac{5}{{\sqrt 3 }}\) |
| D. | 110 : 5 |
| Answer» D. 110 : 5 | |
| 46. |
A merz-price protection is suitable for |
| A. | Transformers |
| B. | Alternators |
| C. | Feeders |
| D. | Transmission lines |
| Answer» C. Feeders | |
| 47. |
Overspeed protection of the alternator is done with the help of |
| A. | Over current relay |
| B. | Alarm |
| C. | Governor |
| D. | Differential relay |
| Answer» D. Differential relay | |
| 48. |
If the time of operation of a relay for unity TMS is 10 secs, the time of operation for 0.5 TMS will be: |
| A. | 20 secs |
| B. | 5 secs |
| C. | 10 secs |
| D. | 15 secs |
| Answer» C. 10 secs | |
| 49. |
A Mho relay is a: |
| A. | Voltage restrained directional relay |
| B. | Voltage controlled over-current relay |
| C. | Directional restrained over-current relay |
| D. | Directional restrained over-voltage relay |
| Answer» B. Voltage controlled over-current relay | |
| 50. |
A thyrite lightning arrester has |
| A. | Inverse resistance characteristics |
| B. | a gap |
| C. | efficient earthing |
| D. | a combination of inverse resistance characteristics and gap |
| Answer» E. | |