McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering .
| 151. |
Why do the SF6 gases have an excellent heat transfer property? |
| A. | Low gaseous viscosity. |
| B. | High dielectric strength. |
| C. | Higher molecular weight. |
| D. | Both (a) and (c) |
| Answer» D. Both (a) and (c) | |
| 152. |
What is the breaking capacity of the air blast circuit breaker? |
| A. | 5000 MVA |
| B. | 6000 MVA |
| C. | 7000 MVA |
| D. | 10000 MVA |
| Answer» C. 7000 MVA | |
| 153. |
In axial blast type of CB, expansion of air takes place from ______________. |
| A. | High pressure to low pressure. |
| B. | Low pressure to high pressure. |
| C. | Always in high pressure. |
| D. | Always in low pressure. |
| Answer» A. High pressure to low pressure. | |
| 154. |
The air blast circuit breakers for 400 kV systems are designed to operate in how much time? |
| A. | 0.1 s |
| B. | 0.5 s |
| C. | 50 ms |
| D. | 100µs |
| Answer» C. 50 ms | |
| 155. |
What is the type of air blast in cross blast type CB? |
| A. | The blast of air is along the ar(C) |
| B. | The blast of air cuts across the ar(C) |
| C. | Both (a) and (b) |
| D. | None of the above. |
| Answer» B. The blast of air cuts across the ar(C) | |
| 156. |
Why is the resistance switching used in a air blast circuit breaker? |
| A. | Reduce the magnitude of fault current. |
| B. | Control the CB operating time. |
| C. | Damp out the fast transient. |
| D. | Change the fault current power factor. |
| Answer» C. Damp out the fast transient. | |
| 157. |
When using air blast circuit breaker, current chopping is a phenomenon observed when |
| A. | A long overhead line is switched off. |
| B. | A bank of capacitors is switched off. |
| C. | A transformer on no load is switched off. |
| D. | A heavy load is switched off. |
| Answer» C. A transformer on no load is switched off. | |
| 158. |
Which type of air is used in air blast circuit breaker? |
| A. | Ionised air |
| B. | Air free from moisture |
| C. | Air should have least CO2 |
| D. | Air must have oil mist. |
| Answer» B. Air free from moisture | |
| 159. |
What is the maximum current upto which fuses can be used? |
| A. | 25 A |
| B. | 50 A |
| C. | 75 A |
| D. | 100 A |
| Answer» D. 100 A | |
| 160. |
What is fusing factor? |
| A. | The ratio of current rating of the fuse to the minimum fusing current |
| B. | The ratio of minimum fusing current to the current rating of the fuse |
| C. | The ratio of maximum fusing current to the current rating of the fuse |
| D. | The ratio of minimum fusing current to the voltage rating of the fuse |
| Answer» A. The ratio of current rating of the fuse to the minimum fusing current | |
| 161. |
For a current upto 10A which material is used as the fusing element? |
| A. | Copper |
| B. | Silver |
| C. | Alloy of lead and tin |
| D. | Zinc |
| Answer» C. Alloy of lead and tin | |
| 162. |
Which among these is the least expensive protection for over current in low voltage system? |
| A. | Rewirable fuse. |
| B. | Isolator. |
| C. | Circuit breaker. |
| D. | Air breaker switch. |
| Answer» A. Rewirable fuse. | |
| 163. |
Which among the following statement is true related to fuse? |
| A. | Greater the current smaller is the time taken by the fuse to blow out. |
| B. | Greater the current greater is the time taken by the fuse to blow out. |
| C. | The current is directly proportion to the blow out time of fuse. |
| D. | Is dependent on the temperature and atmospheric conditions. |
| Answer» A. Greater the current smaller is the time taken by the fuse to blow out. | |
| 164. |
How is the restriking voltage measured? |
| A. | RMS value |
| B. | Peak value |
| C. | Instantaneous value |
| D. | Average value |
| Answer» B. Peak value | |
| 165. |
What is the interrupting medium in the contactor? |
| A. | Air at atmospheric pressure. |
| B. | SF6 gas |
| C. | Oil |
| D. | All of the above. |
| Answer» D. All of the above. | |
| 166. |
Recovery voltage is the value of rms voltage that reappears across the poles of a circuit breaker before_______________ |
| A. | Restriking voltage |
| B. | Final arc extinction |
| C. | Rise of voltage |
| D. | All of the above |
| Answer» B. Final arc extinction | |
| 167. |
Why is it difficult to interrupt a capacitive circuit? |
| A. | The current has a leading power factor. |
| B. | The restriking voltage can be high. |
| C. | Current magnitude is very small. |
| D. | Stored energy in the capacitor is very high. |
| Answer» B. The restriking voltage can be high. | |
| 168. |
Rate of rise of restriking voltage depend on_____________? |
| A. | Type of circuit breaker. |
| B. | Capacitance of the system. |
| C. | Inductance of the system. |
| D. | Both (b) and (c) |
| Answer» D. Both (b) and (c) | |
| 169. |
On what factor does the rate of rise of restriking voltage (RRRV) depend? |
| A. | System voltage. |
| B. | Circuit power factor only |
| C. | Switching conditions |
| D. | Both (b) and (c). |
| Answer» D. Both (b) and (c). | |
| 170. |
In a circuit breaker, the active recovery voltage depends upon which among these? |
| A. | Circuit conditions. |
| B. | Power factor. |
| C. | Both (a) and (b) |
| D. | None of the above |
| Answer» C. Both (a) and (b) | |
| 171. |
What is restriking voltage? |
| A. | The transient voltage that appears across the circuit breaker contacts at the instant of arc extinction. |
| B. | The transient voltage that appears across the circuit breaker contacts at the end of arc extinction. |
| C. | Both (a) and (b) |
| D. | None of the above |
| Answer» A. The transient voltage that appears across the circuit breaker contacts at the instant of arc extinction. | |
| 172. |
For a high speed circuit breaker what will the total clearing time? |
| A. | Few minutes. |
| B. | Few seconds. |
| C. | 1 to 2 cycles. |
| D. | 5 to 20 cycles. |
| Answer» C. 1 to 2 cycles. | |
| 173. |
The interrupting time of a circuit breaker is the period between the instant of _________. |
| A. | Initiation of short circuit and the arc extinction on an opening operation. |
| B. | Energizing the trip circuit and the arc extension on an opening operation. |
| C. | Initiation of short circuit and the parting of primary arc contacts. |
| D. | Energizing of the trip circuit and the parting of primary arc contacts. |
| Answer» B. Energizing the trip circuit and the arc extension on an opening operation. | |
| 174. |
In a circuit breaker, ionisation is facilitated by_________________. |
| A. | Increase in field strength. |
| B. | Increase in mean free length. |
| C. | High temperature of the surrounding medium. |
| D. | All of the above. |
| Answer» D. All of the above. | |
| 175. |
Which of the following should have low value for the contacts and their material? |
| A. | Thermal capacity. |
| B. | Contact resistance. |
| C. | Thermal conductivity. |
| D. | None of above. |
| Answer» B. Contact resistance. | |
| 176. |
The heat produced at the contact point owing to flow of electric current is least affected by_____________________. |
| A. | Temperature of the surrounding medium. |
| B. | Contact resistance. |
| C. | Magnitude of electric current flowing. |
| D. | Duration of flow of current. |
| Answer» A. Temperature of the surrounding medium. | |
| 177. |
The resistance of an electric arc can be increased by |
| A. | Increasing the concentration of ionised particles. |
| B. | Reducing the arc length. |
| C. | Splitting the ar(C) |
| D. | Increasing the arc cross section. |
| Answer» C. Splitting the ar(C) | |
| 178. |
By using low resistance method for arc extension what is the value of arc resistance? |
| A. | Arc resistance is zero. |
| B. | Arc resistance is high |
| C. | Arc resistance is low |
| D. | Arc resistance is very high |
| Answer» C. Arc resistance is low | |
| 179. |
What happens in the arc extinction using high resistance method? |
| A. | Arc resistance is decreased with time. |
| B. | Arc resistance is increased with time. |
| C. | No change it remains same. |
| D. | Arc resistance is kept zero. |
| Answer» B. Arc resistance is increased with time. | |
| 180. |
What is the arc voltage in a circuit breaker? |
| A. | In phase with the arc current. |
| B. | Lagging the arc current by 90° |
| C. | Leading the arc current by 90° |
| D. | Lagging the arcing current by 180° |
| Answer» A. In phase with the arc current. | |
| 181. |
Arcing voltage will be the least in case of |
| A. | Carbon |
| B. | Copper |
| C. | Silver |
| D. | Tungsten |
| Answer» C. Silver | |
| 182. |
How is the initiation of electric arc at the instant of contact separation caused? |
| A. | Thermionic emission of electrons. |
| B. | Field emission of electrons. |
| C. | Both (a) and (b) |
| D. | None of these. |
| Answer» C. Both (a) and (b) | |
| 183. |
The arc resistance depends on which among the following factors? |
| A. | Cross section of the ar(C) |
| B. | Length of the ar(C) |
| C. | Degree of ionization |
| D. | All of the above. |
| Answer» D. All of the above. | |
| 184. |
Which type of tripping is generally preferred for the circuit breaker? |
| A. | Manual |
| B. | Automatically |
| C. | Depending on the voltage level |
| D. | None of the above |
| Answer» B. Automatically | |
| 185. |
Which part of the circuit breaker is helpful in breaking the current? |
| A. | Trip coil. |
| B. | Contacts. |
| C. | Medium |
| D. | Handle. |
| Answer» B. Contacts. | |
| 186. |
When a fault occurs in a high voltage transmission line, what happens first? |
| A. | Circuit breaker operates then the relay. |
| B. | Relay operates and then the circuit breaker. |
| C. | Relay operates, then successively the isolator and the circuit breaker. |
| D. | Isolator operates, then successively the relay and the circuit breaker. |
| Answer» B. Relay operates and then the circuit breaker. | |
| 187. |
Upto what voltage can the liquid type HRC fuses be used? |
| A. | 33 kV |
| B. | 132 kV |
| C. | 66 kV |
| D. | 220 kV |
| Answer» B. 132 kV | |
| 188. |
What is the main advantage of using a fuse? |
| A. | Cheapest type of protection. |
| B. | Inverse time current characteristics. |
| C. | Current limiting effect under short circuit conditions. |
| D. | All of above. |
| Answer» D. All of above. | |
| 189. |
On what basis is the selection of fuse done? |
| A. | Steady loa(D) |
| B. | Fluctuating loa(D) |
| C. | Both (a) and (b) |
| D. | None of these. |
| Answer» C. Both (a) and (b) | |
| 190. |
Upto what voltage a cartridge type of fuse can be used? |
| A. | 400 V |
| B. | 11 kV |
| C. | 20 kV |
| D. | 33 kV |
| Answer» D. 33 kV | |
| 191. |
In a HRC fuse what is the time between the cut off and the final current zero called? |
| A. | Pre - arcing time. |
| B. | Arcing time. |
| C. | Total operating time. |
| D. | None of these. |
| Answer» B. Arcing time. | |
| 192. |
Which material is used in the liquid type of fuse? |
| A. | SF6 |
| B. | Distilled water |
| C. | Carbon tetra chloride. |
| D. | Mineral oil / transformer oil |
| Answer» C. Carbon tetra chloride. | |
| 193. |
What is the advantage of HRC fuses over Rewirable fuses? |
| A. | High speed operation |
| B. | High rupturing capacity |
| C. | No ageing effect. |
| D. | All of the above. |
| Answer» D. All of the above. | |
| 194. |
If the strands of the fusing wire are twisted, what happens to the fusing current? |
| A. | Increases |
| B. | Reduces. |
| C. | No change/ remains same |
| D. | Depends on the value of current, increases or decreases. |
| Answer» B. Reduces. | |
| 195. |
What is the typical value of the pre arcing time? |
| A. | 0.1 |
| B. | 0.01 |
| C. | 0.001 |
| D. | 0.0001 |
| Answer» C. 0.001 | |
| 196. |
Outdoor switchgear is generally used for voltage beyond |
| A. | 11 KV |
| B. | 33 KV |
| C. | 66 KV |
| D. | 132 KV |
| Answer» C. 66 KV | |
| 197. |
The least expensive protection for over current in low-voltage system is |
| A. | Rewirable fuse |
| B. | Isolator |
| C. | Circuit breaker |
| D. | Air-break switch |
| Answer» A. Rewirable fuse | |
| 198. |
Purpose of backup protection is |
| A. | To increase the speed |
| B. | To increase a reach |
| C. | To leave no blind spot |
| D. | To guard against failure of primary |
| Answer» D. To guard against failure of primary | |
| 199. |
We do not require any protection against prime mover failure in case of |
| A. | Turbo generator sets |
| B. | Hydro generator sets |
| C. | Diesel engine driven alternators |
| D. | Back pressure turbo generators |
| Answer» A. Turbo generator sets | |
| 200. |
For the protection of stator winding of an alternate against internal fault involving ground the relay used is a |
| A. | Biased differential relay |
| B. | Directional over-current relay |
| C. | Plain impedance relay |
| D. | Buchholz relay |
| Answer» A. Biased differential relay | |
Done Studing? Take A Test.
Great job completing your study session! Now it's time to put your knowledge to the test. Challenge yourself, see how much you've learned, and identify areas for improvement. Don’t worry, this is all part of the journey to mastery. Ready for the next step? Take a quiz to solidify what you've just studied.