MCQOPTIONS
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MCQOPTIONS
This section includes 49 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. |
In a system of 132 kV, the line to ground capacitance is 0.05 μF and the inductance is 8 H. Determine the voltage appearing across the pole of a circuit breaker if a magnetising current of 7 A is interrupted. |
| A. | 23.99 kV |
| B. | 54.88 kV |
| C. | 88.54 kV |
| D. | 99.23 kV |
| Answer» D. 99.23 kV | |
| 2. |
Current rating is not necessary in the case of |
| A. | Switch and Isolators |
| B. | Isolators |
| C. | Switch |
| D. | Circuit Breakers |
| Answer» C. Switch | |
| 3. |
By which material the high voltage fuse element is generally made |
| A. | Copper |
| B. | Nickel |
| C. | Iron alloy |
| D. | Silver |
| Answer» E. | |
| 4. |
A circuit breaker is rated as a 1450 A, 1,200 MVA, 33 kV, 3 s, 3-phase oil circuit breaker.Find the breaking capacity. |
| A. | 1,200 MVA |
| B. | 33 kV |
| C. | 3 s |
| D. | 1,450 A |
| Answer» B. 33 kV | |
| 5. |
At what level of current flow during electric shock death is possible. |
| A. | 1 to 8 milli amp |
| B. | 50 to 100 milli amp |
| C. | 10 to 20 milli amp |
| D. | 20 to 50 milli amp |
| Answer» C. 10 to 20 milli amp | |
| 6. |
For achieving grading, the ratio between major and minor fuses shall be _______ or more. |
| A. | 1 : 2 |
| B. | 2: 1 |
| C. | 3 : 1 |
| D. | 1 : 3 |
| Answer» C. 3 : 1 | |
| 7. |
Lightning arrestor should be located |
| A. | away from the circuit breaker |
| B. | near the circuit breaker |
| C. | near the transformer |
| D. | away from the transformer |
| Answer» D. away from the transformer | |
| 8. |
A Bimetallic strip breaks the circuit when: |
| A. | Resistance increases |
| B. | Current rises above its setting value |
| C. | Current decreases to zero |
| D. | Voltage decreases |
| Answer» C. Current decreases to zero | |
| 9. |
Identify the correct relationship regarding the rating of a circuit breaker. |
| A. | Symmetrical breaking capacity = 2.55 × Making capacity |
| B. | Making capacity = Symmetrical breaking capacity |
| C. | Making capacity = 5.55 × Symmetrical breaking capacity |
| D. | Making capacity = 2.55 × Symmetrical breaking capacity |
| Answer» E. | |
| 10. |
A fuse is a safety device used for the purpose of protecting a circuit against ________ |
| A. | Under current |
| B. | Leakage current |
| C. | Excess current |
| D. | Under voltage |
| Answer» D. Under voltage | |
| 11. |
A 3-phase circuit breaker is rated at 3300 MVA, 33 kV. Its making current will be |
| A. | 100/√3 kA |
| B. | 100 kA |
| C. | 255/√3 kA |
| D. | 255 kA |
| Answer» D. 255 kA | |
| 12. |
A bus coupler circuit breaker is utilized in a substation for |
| A. | Joining the transmission line with station bus bar |
| B. | Joining main and transfer bus in a substation |
| C. | Joining the generator with transformer |
| D. | Joining the neutral of generator with earth |
| Answer» C. Joining the generator with transformer | |
| 13. |
Circuit breakers cut off the main supply immediately during |
| A. | Short circuit |
| B. | Low voltage supply |
| C. | Spikes |
| D. | Load shedding |
| Answer» B. Low voltage supply | |
| 14. |
A 50 Hz, 11 kV, 3 phase alternators with earthed neutral having a reactance of 3 ohms per phase and is connected to a bus bar through a circuit breaker if the distributed capacitance up to CB between the phase and neutral is 0.01 μ F. What is the frequency of oscillations? |
| A. | 12,500 Hz |
| B. | 10000 Hz |
| C. | 16,286 Hz |
| D. | 13,265 Hz |
| Answer» D. 13,265 Hz | |
| 15. |
In HRC fuse the time between cut-off and final current zero is called |
| A. | the pre-arcing time |
| B. | the arcing time |
| C. | the total operating time |
| D. | none of these |
| Answer» C. the total operating time | |
| 16. |
________ does not have any repairable component: |
| A. | Air Blast CB |
| B. | MCB |
| C. | OCB |
| D. | Air Break |
| Answer» C. OCB | |
| 17. |
Current chopping usually occurs in: |
| A. | MCB |
| B. | Oil circuit breaker |
| C. | Minimum OCB |
| D. | Airblast circuit breaker |
| Answer» E. | |
| 18. |
Arc in a circuit breaker is interrupted at: |
| A. | Maximum current |
| B. | Maximum voltage |
| C. | Zero current |
| D. | Minimum voltage |
| Answer» D. Minimum voltage | |
| 19. |
Current rating of fuse is _______ to the operating temperature |
| A. | inversely proportional |
| B. | directly proportional |
| C. | equal |
| D. | exponential |
| Answer» B. directly proportional | |
| 20. |
MCCB stands for ________ circuit breaker. |
| A. | mixed case |
| B. | mains case |
| C. | modulated case |
| D. | moulded case |
| Answer» E. | |
| 21. |
Arcing contacts in a circuit breaker is usually made of: |
| A. | Copper tungsten alloy |
| B. | Zinc mercury amalgam |
| C. | Porcelain |
| D. | Graphite |
| Answer» B. Zinc mercury amalgam | |
| 22. |
Quantity by which circuit breakers are rated is |
| A. | maximum voltage |
| B. | frequency |
| C. | interruption time |
| D. | All of the above |
| Answer» E. | |
| 23. |
If the operating current is between 10 A to 100 A, which device will be used for breaking the circuit safely? |
| A. | Bare copper wire |
| B. | MCCB |
| C. | MCB |
| D. | Bare aluminum wire |
| Answer» C. MCB | |
| 24. |
According to Indian Standards, the breakdown voltage of new untreated oil should be |
| A. | 10 kV |
| B. | 20 kV |
| C. | 30 kV |
| D. | 60 kV |
| Answer» D. 60 kV | |
| 25. |
An HRC fuse does NOT use which of the following? |
| A. | Silver |
| B. | Ceramic |
| C. | Zinc |
| D. | Lead |
| Answer» C. Zinc | |
| 26. |
In a circuit breaker, ionisation is not facilitated by: |
| A. | Material of contacts |
| B. | Increase of mean path |
| C. | Increase of filed strength |
| D. | High temperature of surrounding medium |
| Answer» B. Increase of mean path | |
| 27. |
In connection with the extinction in circuit breaker, resistance switching is employed where in a resistance is placed in parallel with the poles of the circuit breaker as shown in the figure. This process introduces damping in the LC circuit. For critical damping the value of ‘r’ should be equal to |
| A. | \(\sqrt {\frac{C}{L}} \) |
| B. | \(0.5\sqrt {\frac{C}{L}} \) |
| C. | \(0.5\sqrt {\frac{L}{C}} \) |
| D. | \(\frac{1}{{2\pi }}\sqrt {\frac{L}{C}} \) |
| Answer» D. \(\frac{1}{{2\pi }}\sqrt {\frac{L}{C}} \) | |
| 28. |
In relation to electrical drawing, the following symbol is used for? |
| A. | Buzzer |
| B. | Horn |
| C. | Lightning arrester |
| D. | Power circuit breaker |
| Answer» E. | |
| 29. |
If the generating station capacity increases from 10 MVA to 20 MVA, the rating requirement of the circuit breaker is ____________. |
| A. | Remains the same but the physical size of the circuit breaker increases |
| B. | Increases |
| C. | Decreases |
| D. | Stays the same |
| Answer» C. Decreases | |
| 30. |
In a DC circuit breaker, the current interruption and arc quenching is obtained by: |
| A. | natural zero current interruption |
| B. | low-resistance interruption |
| C. | high-resistance interruption |
| D. | increasing the arc current |
| Answer» D. increasing the arc current | |
| 31. |
Depending upon the voltage to be handled, switchgear may be broadly classified into: |
| A. | Outdoor type |
| B. | None of these |
| C. | Indoor type |
| D. | Both Outdoor type and Indoor type |
| Answer» E. | |
| 32. |
In gas insulated switchgears _____ gas is used at an above pressure. |
| A. | SF6 |
| B. | CO |
| C. | CO2 |
| D. | NO |
| Answer» B. CO | |
| 33. |
A circuit breaker is a device that is used for protection of the circuit. The circuit breaker is an example of:- |
| A. | Arresters |
| B. | Conductor |
| C. | None of these |
| D. | Switchgear |
| Answer» E. | |
| 34. |
For protection of rotating machines against lightning surges __________ is used. |
| A. | lightning arrester |
| B. | capacitor |
| C. | combination of lightning arrester and capacitor |
| D. | lightning conductor and arrester |
| Answer» D. lightning conductor and arrester | |
| 35. |
In a 132 kV system, the series inductance up to the point of circuit breaker location is 50 mH. The shunt capacitance at the circuit breaker terminal is 0.05 μF. The critical value of resistance required to be connected across the circuit breaker contacts which will given no transient oscillation is: |
| A. | 50000 Ω |
| B. | 50 Ω |
| C. | 5000 Ω |
| D. | 500 Ω |
| Answer» E. | |
| 36. |
In power system for 132 kV and above, the circuit breaker preferred is ________. |
| A. | Minimum oil |
| B. | Miniature |
| C. | SF6 |
| D. | Vacuum |
| Answer» D. Vacuum | |
| 37. |
Isolator operates on ________ conditions. |
| A. | Some times on load and sometimes no load |
| B. | On load |
| C. | No load |
| D. | Full load |
| Answer» D. Full load | |
| 38. |
Fusing factor is the ratio of: |
| A. | current rating of fuse to the minimum fusing current |
| B. | minimum fusing current to the current rating of fuse |
| C. | minimum fusing current to the fault current |
| D. | minimum fusing current to the arcing time constant |
| Answer» C. minimum fusing current to the fault current | |
| 39. |
In which terminology is the rupture capacity of the fuse expressed? |
| A. | kA |
| B. | kWh |
| C. | MVA |
| D. | kV |
| Answer» D. kV | |
| 40. |
Essential features of switchgear are: |
| A. | Absolutely certain discrimination |
| B. | All of these |
| C. | Complete reliability |
| D. | Quick operation |
| Answer» C. Complete reliability | |
| 41. |
In case of circuit breakers, the rate of rise of restriking voltage (RRRV) is expressed in |
| A. | kV/μs |
| B. | μs/kV |
| C. | kV |
| D. | kA/μs |
| Answer» B. μs/kV | |
| 42. |
For standard duty cartridge fuses, what is the fusing factor equal to? |
| A. | 1.65 |
| B. | 1.45 |
| C. | 1.85 |
| D. | 1.25 |
| Answer» C. 1.85 | |
| 43. |
In the event of a fault on the connected circuit, a circuit breaker will operate |
| A. | Automatically |
| B. | Manually |
| C. | Manually through control switch |
| D. | Depending on the design |
| Answer» B. Manually | |
| 44. |
Let ‘L’ be the inductance of the system, ‘C’ be the capacitance of the system, ‘I’ be the instantaneous value of are current, and ‘V’ be the instantaneous value of capacitor voltage, which appears across the breaker when it opens. The prospective voltage or arc voltage is determined as: |
| A. | \(V = I /{\sqrt {{L}{C}}}\) |
| B. | \(V = I\;\sqrt {\frac{L}{C}}\) |
| C. | \(V = I {\sqrt {{L}{C}}}\) |
| D. | \(V = I\;\sqrt {\frac{C}{L}}\) |
| Answer» C. \(V = I {\sqrt {{L}{C}}}\) | |
| 45. |
Air Blast Circuit breaker is employed among which of the following?i. Arc furnace dutyii. Traction system |
| A. | Only i |
| B. | Only ii |
| C. | i and ii both |
| D. | Neither (i) nor (ii) |
| Answer» D. Neither (i) nor (ii) | |
| 46. |
If normal system voltage is 415 V, rated voltage of circuit breaker will be |
| A. | 400 V |
| B. | 415 V |
| C. | 440 V |
| D. | Any value above 415 V |
| Answer» D. Any value above 415 V | |
| 47. |
Lightning arrestors connected in power system protect electrical equipments from: |
| A. | Frequency fluctuation |
| B. | Over-current due to indirect lightning stroke |
| C. | Over-voltages due to indirect lightning stroke |
| D. | Direct stroke of lightning |
| Answer» D. Direct stroke of lightning | |
| 48. |
On what factors does the current carrying capacity of a fuse depend?I) Size of fuse wireII) Fuse materialIII) Surrounding of the fuseChoose the correct answer from the options given below. |
| A. | Only I |
| B. | Only I and III |
| C. | Only II and III |
| D. | I, II and III |
| Answer» E. | |
| 49. |
A short circuit test on 3-pole, 132 kV circuit breaker gave results as fault power factor 0.4, recovery voltage 90% full time value, symmetrical breaking current, the frequency of oscillations of restriking voltage 16 kHz. Neutral is grounded and fault is ungrounded. The instantaneous value of recovery voltage will be |
| A. | 134 kV |
| B. | 151 kV |
| C. | 247 kV |
| D. | 763 kV |
| Answer» B. 151 kV | |