MCQOPTIONS
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MCQOPTIONS
This section includes 20 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. |
A blocked electric current of 4000 A is passing through the primary side of a converter having 400/5 A current. The plug setting of the electric current relay is set at 50% at the secondary of the electric current converter. What will be the plug setting multiplier? |
| A. | 20 |
| B. | 30 |
| C. | 10 |
| D. | 40 |
| Answer» B. 30 | |
| 2. |
For differential protection of power transformer (delta-delta) the current transformers will have |
| A. | Delta-delta connection |
| B. | Star-delta connection |
| C. | Star-star connection |
| D. | Delta-star connection |
| Answer» D. Delta-star connection | |
| 3. |
Impedance relay is used on______ transmission lines. |
| A. | Short |
| B. | Medium |
| C. | Long |
| D. | All |
| Answer» C. Long | |
| 4. |
A 11 kV 100 MVA alternator is grounded through a resistance of 4 Ω. The C.T.s have a ratio of 500/5. The relay is set to operate when there is an out of balance current of 2 A. What percentage of generator winding will be protected by the percentage differential protection scheme? |
| A. | 93.7 |
| B. | 6.3 |
| C. | 87.4 |
| D. | 84.5 |
| Answer» D. 84.5 | |
| 5. |
If for an IDMT relay with a plug setting of 50% and a CT ration of 400/5, the current is 3000 A, then the plug setting multiplier would be: |
| A. | 7.5 |
| B. | 15 |
| C. | 18.75 |
| D. | 37.5 |
| Answer» C. 18.75 | |
| 6. |
In case of short-tie-line fed at both the ends, for protection |
| A. | reactance relay is the best choice |
| B. | ohm relay is the best choice |
| C. | mho relay is the best choice |
| D. | Both (1) and (3) |
| Answer» D. Both (1) and (3) | |
| 7. |
Buchholz relay is used on: |
| A. | Oil cooled transformer |
| B. | Air cooled transformer |
| C. | Welding transformer |
| D. | Furnace transformer |
| Answer» B. Air cooled transformer | |
| 8. |
A 3 – Phase transformer rated for 33 kV/ 11kV is connected in delta/star as shown in figure. The current transformers (CTs) on low land high voltage sides have a ratio of 500/5. Find the current \({i_1}\) and \({i_2}\), of the fault current is 300 A as shown in figure |
| A. | \({i_1} = \frac{1}{{\sqrt 3 A}},{i_2} = 0A\) |
| B. | \({i_1} = 0A\), \({i_2} = 0A\) |
| C. | \({i_1} = 0A,{i_2} = \frac{1}{{\sqrt 3 A}}\) |
| D. | \({i_1} = \frac{1}{{\sqrt 3 A}},{i_2} = \frac{1}{{\sqrt 3 A}}\) |
| Answer» B. \({i_1} = 0A\), \({i_2} = 0A\) | |
| 9. |
Distance protection relay is used in: |
| A. | Transformer |
| B. | Generator |
| C. | Transmission line |
| D. | Motor |
| Answer» D. Motor | |
| 10. |
Determine operating current of the relay, for 5 A, 2.2-sec IDMT rating, and 125% relay setting? |
| A. | 11 A |
| B. | 4 A |
| C. | 12.5 A |
| D. | 6.25 A |
| Answer» E. | |
| 11. |
An electromagnetic attraction type relay operates on ______. |
| A. | Pulsated DC |
| B. | AC only |
| C. | DC only |
| D. | Both AC & DC |
| Answer» E. | |
| 12. |
In induction type directional over current relay the driving torque is due to interaction of magnetic fields derived from |
| A. | current in the potential coil |
| B. | both voltage and current in the relay windings |
| C. | directional element and non-directional element |
| D. | non-directional element and the trip circuit |
| Answer» D. non-directional element and the trip circuit | |
| 13. |
Directional overcurrent relay is used for the protection of |
| A. | long transmission lines |
| B. | large power transformers |
| C. | ring main distribution lines |
| D. | radial distribution lines |
| Answer» D. radial distribution lines | |
| 14. |
If the PSM is 8, the relay setting is 125% and CT ratio is 400 : 1, then the value of fault current will be: |
| A. | 4550 A |
| B. | 5000 A |
| C. | 3000 A |
| D. | 4000 A |
| Answer» E. | |
| 15. |
In case of transformer Buchholz relay is used to protect from ________. |
| A. | High voltage surges |
| B. | Overload faults |
| C. | Incipient faults |
| D. | Earth faults |
| Answer» D. Earth faults | |
| 16. |
A distance relay with inherent directional property is known as |
| A. | Buchholtz relay |
| B. | Admittance relay |
| C. | Directional over current relay |
| D. | Directional switched relay |
| Answer» C. Directional over current relay | |
| 17. |
IDMT full form is: |
| A. | Inverse Distance maximum Time Relay |
| B. | Inverse Definite Minimum Time Relay |
| C. | Inverse Distance Minimum Time Relay |
| D. | Inverse Definite Maximum Time Relay |
| Answer» C. Inverse Distance Minimum Time Relay | |
| 18. |
A relay is connected to a 400/5 A current transformer and set for 150%. The primary fault current of 2400 A needs a plug setting multiplier of |
| A. | 2 |
| B. | 4 |
| C. | 6 |
| D. | 8 |
| Answer» C. 6 | |
| 19. |
An earth fault relay has a setting of 150% and a current rating of 5 A. It is connected to a current transformer of ratio 200:5. The current in the primary for which the relay picks up is |
| A. | 7.5 A |
| B. | 20 A |
| C. | 300 A |
| D. | 1500 A |
| Answer» D. 1500 A | |
| 20. |
A power system with two generators is shown in the figure below. The system (generators, buses and transmission lines) is protected by six overcurrent relays R1 to R6. Assuming a mix of directional and non-directional relays at appropriate locations, the remote backup relays for R4 are |
| A. | R1, R2 |
| B. | R2, R6 |
| C. | R2, R5 |
| D. | R1, R6 |
| Answer» E. | |