MCQOPTIONS
Saved Bookmarks
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.
| 51. |
For reliable protection of overhead transmission lines from direct lightning strokes using ground wires, the protection angle ‘a’ between the vertical line through the ground wire axis and the line passing from the ground wire axis to the outer most line conductor should be _______. |
| A. | 10° - 15° |
| B. | 50° - 60° |
| C. | 20° - 30° |
| D. | 40° - 50° |
| Answer» D. 40° - 50° | |
| 52. |
________ Relays are best suited for protection of radial feeders. |
| A. | Overload |
| B. | Definite time current |
| C. | Induction type |
| D. | Earth leakage |
| Answer» C. Induction type | |
| 53. |
A pilot relay is used for |
| A. | High speed tripping |
| B. | Delayed tripping |
| C. | Pre-set tripping |
| D. | No tripping |
| Answer» B. Delayed tripping | |
| 54. |
In oxide film arrester, when heated, lead peroxide gets converted to: |
| A. | Black lead |
| B. | White lead |
| C. | Graphite |
| D. | Red lead |
| Answer» E. | |
| 55. |
Main purpose of using oil in oil circuit breaker is to: |
| A. | Provide insulation between oil circuit breaker |
| B. | Provide cooling of contacts |
| C. | Quenching arc |
| D. | None of these |
| Answer» D. None of these | |
| 56. |
Differential relays are used to protect the equipment against: |
| A. | Internal faults |
| B. | Reverse current |
| C. | Over voltage |
| D. | Over current |
| Answer» B. Reverse current | |
| 57. |
Plug setting Multiplier (P.S.M) of relay is the ratio: |
| A. | pick up current to normal current |
| B. | rated secondary current of CT to rated current of CT |
| C. | fault current in circuit breaker to normal current |
| D. | fault current in relay coil to pick up current |
| Answer» E. | |
| 58. |
Merz price protection scheme is the one from: |
| A. | differential protection |
| B. | over current protection |
| C. | earth fault protection |
| D. | distance protection |
| Answer» B. over current protection | |
| 59. |
Mho relay is normally used for the protection of _______ |
| A. | Long transmission lines |
| B. | Medium transmission lines |
| C. | Short transmission lines |
| D. | Transformers |
| Answer» B. Medium transmission lines | |
| 60. |
Bias setting of transformer differential relay cannot avoid maloperation due toa) External faultb) CT saturationc) CT mismatchingd) Over-voltage on source side of the transformer |
| A. | A only |
| B. | D only |
| C. | B and C only |
| D. | B only |
| Answer» C. B and C only | |
| 61. |
Protection against negative sequence currents is provided for: |
| A. | transformers |
| B. | generators |
| C. | transmission lines |
| D. | None of the above |
| Answer» C. transmission lines | |
| 62. |
Location of lighting arrester is near a |
| A. | Generator |
| B. | Transformer |
| C. | Busbar |
| D. | Circuit breaker |
| Answer» C. Busbar | |
| 63. |
Number of immobile contacts in double oil circuit breaker is: |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» C. 3 | |
| 64. |
______ gives an alarm when faults happen and is installed in oil immersed transformers. |
| A. | Hybrid Relay |
| B. | Buchholz Relay |
| C. | Latching Relay |
| D. | Non-Latching Relay |
| Answer» C. Latching Relay | |
| 65. |
A circuit is disconnected by isolators when: |
| A. | The circuit breaker is not open |
| B. | There is no current in the line |
| C. | The line is on full load |
| D. | Line is energized |
| Answer» C. The line is on full load | |
| 66. |
A circuit breaker is a: |
| A. | Protective device |
| B. | Controlling device |
| C. | Circuit interrupting device |
| D. | All of these |
| Answer» E. | |
| 67. |
Overload relays are of ________ type. |
| A. | Thermal |
| B. | Electromagnetic |
| C. | Solid-state |
| D. | All of these |
| Answer» E. | |
| 68. |
For complete protection of a 3 – phase transmission line, we require |
| A. | Three phase and three earth fault relays |
| B. | Three phase and two earth fault relays |
| C. | Two phase and two earth fault relays |
| D. | Two-phase and one – earth fault relay |
| Answer» E. | |
| 69. |
During arc extinction SF6 gets |
| A. | Decomposed into SF4 and SF2 |
| B. | Decomposed into S and F ions |
| C. | Reduce to SF2 |
| D. | Oxidised |
| Answer» B. Decomposed into S and F ions | |
| 70. |
A relay in a power system is a/an: |
| A. | Automatic device that senses an abnormal condition in an electrical circuit and closes its contacts |
| B. | Manual device that senses an abnormal condition in an electrical circuit and closes its contacts |
| C. | Automatic device that senses an abnormal condition in an electrical circuit and opens its contacts |
| D. | Automatic device that senses an abnormal condition in an electronic circuit and opens its contacts |
| Answer» B. Manual device that senses an abnormal condition in an electrical circuit and closes its contacts | |
| 71. |
HRC fuses on a transformer provided protection against |
| A. | Insulation failure |
| B. | Internal faults |
| C. | External faults |
| D. | Low oil level |
| Answer» D. Low oil level | |
| 72. |
Latching relays |
| A. | Hold their contact in position after power is cut off |
| B. | Hold their contact in position after power is on |
| C. | Hold the default position after power is off |
| D. | None of the above |
| Answer» B. Hold their contact in position after power is on | |
| 73. |
A relay which has no moving parts and performs measurement with solid state circuit is called |
| A. | Differential relay |
| B. | Static relay |
| C. | Induction relay |
| D. | Thermal relay |
| Answer» C. Induction relay | |
| 74. |
In 3-phase induction motor, one phase is blown. To protect the motor from this condition _______ is used. |
| A. | Relay preventer |
| B. | Distance relay |
| C. | Single phase inverter |
| D. | Differential relay |
| Answer» B. Distance relay | |
| 75. |
Consider the following statements with respect to a relay:1. A relay is energized if NC contacts are opened.2. The pickup current is the minimum relay coil current required to keep a relay energized.Which of the above statements is/are correct? |
| A. | 1 only |
| B. | 2 only |
| C. | Both 1 and 2 |
| D. | Neither 1 nor 2 |
| Answer» B. 2 only | |
| 76. |
Lightning arrester is normally connected between _________ at the substation |
| A. | phase and phase |
| B. | phase and ground |
| C. | Both (1) and (2) |
| D. | None of the above |
| Answer» C. Both (1) and (2) | |
| 77. |
For the protection of a delta-star transformer using differential protection scheme, which of the following CT connection is used? |
| A. | Primary Star, Secondary Star |
| B. | Primary Delta, Secondary Star |
| C. | Primary Star, Secondary Delta |
| D. | Primary Delta, Secondary Delta |
| Answer» D. Primary Delta, Secondary Delta | |
| 78. |
If the fault current is 2000 amps, the relay setting is 50% and the CT ratio is 400/5, then the plug setting multiplier will be _____ |
| A. | 25 |
| B. | 15 |
| C. | 50 |
| D. | 10 |
| Answer» E. | |
| 79. |
A device, which detects the fault and supplies information to the breaker for circuit interruption is called: |
| A. | Circuit breaker |
| B. | Arrester |
| C. | Conductor |
| D. | Relay |
| Answer» E. | |
| 80. |
A fuse is provided in an electric circuit to: |
| A. | Reduce the power consumption in the circuit |
| B. | Limit the current in the circuit |
| C. | Safeguard the circuit against heavy current |
| D. | Increase the current in the circuit |
| Answer» D. Increase the current in the circuit | |
| 81. |
For the impedance relaying schemes, calculate the impedance using the |
| A. | Fundamental component of the post-fault current |
| B. | Transient component of the post-fault current |
| C. | Fundamental as well as transient component of the fault current |
| D. | None of the above |
| Answer» D. None of the above | |
| 82. |
Match the followingCircuit breaker (CB)Arc extinction medium1. Minimum oil CBa. Oil2. Air blast CBb. Air at atmospheric pressure3. SF6 CBc. SF6 gas4. Air break CBd. Compressed air |
| A. | 1 - a, 2 - b, 3 - c, 4 - d |
| B. | 1 - d, 2 - b, 3 - c, 4 - a |
| C. | 1 - c, 2 - b, 3 - a, 4 - d |
| D. | 1 - a, 2 - d, 3 - c, 4 - b |
| Answer» E. | |
| 83. |
Breaking capacity of a circuit breaker is usually expressed in: |
| A. | Volts |
| B. | Amperes |
| C. | MVA |
| D. | MW |
| Answer» D. MW | |
| 84. |
An effective method of providing protection to transmission lines against direct lightning strokes is by the use of |
| A. | Earthing screen |
| B. | Over head ground wires |
| C. | Lightning arrester |
| D. | None of these |
| Answer» C. Lightning arrester | |
| 85. |
Earth fault relays are |
| A. | direction relays |
| B. | non-directional relays |
| C. | short operate time relays |
| D. | long operate time relays |
| Answer» B. non-directional relays | |
| 86. |
HRC fuse provides best protection against |
| A. | Open circuit |
| B. | Overload |
| C. | Reverse current |
| D. | Short circuit |
| Answer» E. | |
| 87. |
A relay used for protection of motors against overload is |
| A. | Impedance relay |
| B. | Electromagnetic attraction type |
| C. | Thermal relay |
| D. | Buchholz’s relay |
| Answer» D. Buchholz’s relay | |
| 88. |
Harmonic restraint feature is imparted to transformer differential relays to prevent its maloperation due to |
| A. | power swing |
| B. | magnetizing inrush current |
| C. | mismatch of CT ratios |
| D. | unequal voltages on the two sides of transformer |
| Answer» C. mismatch of CT ratios | |
| 89. |
If a combination of HRC fuse and circuit breaker is used, the C.B. operates for |
| A. | Low overload currents |
| B. | Short circuit current |
| C. | Under all abnormal current |
| D. | The combination is never used in practice |
| Answer» B. Short circuit current | |
| 90. |
For the measurement of peak value of an impulse voltage, which of the following Disruptive Discharge Voltage (DDV) is measured? |
| A. | Zero |
| B. | 10% DDV |
| C. | 50% DDV |
| D. | 100% DDV |
| Answer» D. 100% DDV | |
| 91. |
An over–current relay is said to over reach when it operates at a current ________. |
| A. | Higher than its setting |
| B. | Equal to its setting |
| C. | 2/3rd of its setting |
| D. | Lower than its setting |
| Answer» E. | |
| 92. |
For which of the following thermal bimetal is used? |
| A. | overload relay |
| B. | Generator |
| C. | in accelerometer |
| D. | in the motor |
| Answer» B. Generator | |
| 93. |
Buchholz relay is a protection relay used in oil immersed transformers. Under what conditions does Buchholz Relay will NOT operate? |
| A. | Gas bubbles are formed inside the transformer due to faults |
| B. | Level of transformer oil falls that leads to no movement of baffle plate |
| C. | Transformer oil flows rapidly from conservation tank to the main |
| D. | Level of transformer oil falls that leads to movement of baffle plate |
| Answer» C. Transformer oil flows rapidly from conservation tank to the main | |