MCQOPTIONS
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MCQOPTIONS
This section includes 11 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. |
The frequency of the carrier in the case of carrier-current-pilot scheme is in the range of _________ |
| A. | 50 kHz-500 kHz |
| B. | 1 kHz-10 kHz |
| C. | 25 kHz-50 kHz |
| D. | 15 kHz-25kHz |
| Answer» B. 1 kHz-10 kHz | |
| 2. |
If a transformer is provided with differentially connected relay. To prevent the mal operation of the relay, the relay restraining coil is biased with ______________ |
| A. | 3rd harmonic |
| B. | 2nd harmonic |
| C. | 7th harmonic |
| D. | 5th harmonic |
| Answer» C. 7th harmonic | |
| 3. |
If a transformer is provided with differentially connected relay. To prevent the mal operation of the relay, the relay relay operating coil is biased with ______ |
| A. | 3rd harmonic |
| B. | 2nd harmonic |
| C. | 7th harmonic |
| D. | 5th harmonic |
| Answer» E. | |
| 4. |
While a transformer is energised, the differentially connected relay will |
| A. | mal operate |
| B. | not mal operate |
| C. | mal operate for lagging loads |
| D. | never mal operate |
| Answer» B. not mal operate | |
| 5. |
The neutral of the three phase 20 MVA, 11kV alternator is earthed through a resistance of 5 ohms, the relay is set to operate when there is an out of balance current of 1.5 A. The CTs have a ratio of 100/5. What should be the minimum value of the earthing resistance to protect 90% of winding? |
| A. | 2.12 Ω |
| B. | 1.12 Ω |
| C. | 4.24 Ω |
| D. | 3.24 Ω |
| Answer» B. 1.12 Ω | |
| 6. |
The neutral of the three phase 20 MVA, 11kV alternator is earthed through a resistance of 5 ohms, the relay is set to operate when there is an out of balance current of 1.5 A. The CTs have a ratio of 100/5. What percentage of the winding is protected against L-G faults? |
| A. | 76.4 |
| B. | 23.6 |
| C. | 73 |
| D. | None of the mentioned |
| Answer» C. 73 | |
| 7. |
The neutral of the three phase 20 MVA, 11kV alternator is earthed through a resistance of 5 ohms, the relay is set to operate when there is an out of balance current of 1.5 A. The CTs have a ratio of 100/5. What percentage of the winding is protected against earth faults? |
| A. | 76.4 |
| B. | 77.8 |
| C. | 73 |
| D. | None of the mentioned |
| Answer» B. 77.8 | |
| 8. |
The neutral of the three phase 20 MVA, 11kV alternator is earthed through a resistance of 5 ohms, the relay is set to operate when there is an out of balance current of 1.5 A. The CTs have a ratio of 100/5. What percentage of the winding is protected against L-G faults? |
| A. | 76.4 |
| B. | 77.8 |
| C. | 73 |
| D. | None of the mentioned |
| Answer» E. | |
| 9. |
A three phase transformer having a line voltage ratio of 400/33000 V is connected in the star-delta. The CTs on the 400V side have a CT ratio of 1000/5. What will be the current through the pilot wire? |
| A. | 5√3 A |
| B. | 5/√3 A |
| C. | 5 A |
| D. | 1/5 A |
| Answer» B. 5/√3 A | |
| 10. |
A three phase transformer having a line voltage ratio of 400/33000 V is connected in the star-delta. The CTs on the 400V side have a CT ratio of 1000/5. What must be the ratio of CTs on the 33000 side? |
| A. | 7/5 |
| B. | 5/7 |
| C. | 3/5 |
| D. | 5/2 |
| Answer» B. 5/7 | |
| 11. |
The factor which influences the acr de ionisation dominantly ________ |
| A. | line voltage |
| B. | magnitude of transient fault current |
| C. | speed of reclosure |
| D. | all of the mentioned |
| Answer» B. magnitude of transient fault current | |