McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering .
| 201. |
For the protection of a large squirrel cage induction motor against single phase normally |
| A. | An over-current relay is used |
| B. | Differential relay is used |
| C. | Directional relay is used |
| D. | Negative sequence current sensitive relay is used |
| Answer» D. Negative sequence current sensitive relay is used | |
| 202. |
The most commonly used method for the protection of three phase feeder is |
| A. | Time graded protection |
| B. | Differential protection |
| C. | Reverse power protection |
| D. | None of the above |
| Answer» B. Differential protection | |
| 203. |
Which is the pilotless protection method for feeder line ? |
| A. | Differential protection |
| B. | Carrier current protection |
| C. | Time credit protection |
| D. | None of the above |
| Answer» B. Carrier current protection | |
| 204. |
Time graded protection of a radial feeder can be achieved by using |
| A. | Definite time relay |
| B. | Inverse time relay |
| C. | Both definite and inverse time relays |
| D. | None of the above |
| Answer» C. Both definite and inverse time relays | |
| 205. |
Pilot-wire protection scheme is the most economical and provides high speed relaying for |
| A. | Short length of lines upto 15 km |
| B. | Medium length of lives up to 60 km |
| C. | Long length of lines up to 200 km |
| D. | All of the above |
| Answer» A. Short length of lines upto 15 km | |
| 206. |
Problems associated with differential protection is/are |
| A. | Magnetising inrush current |
| B. | Mismatching characteristics of CTs |
| C. | Charge of ratio as a result of tapping |
| D. | All of the above |
| Answer» D. All of the above | |
| 207. |
For the protection of transformers, harmonic restraint is used to guard against |
| A. | Magnetising inrush current |
| B. | Unbalanced operation |
| C. | Lightning |
| D. | Switching over-voltage |
| Answer» A. Magnetising inrush current | |
| 208. |
The types of faults that occur in electric motors are |
| A. | Stator |
| B. | Rotor |
| C. | Overload |
| D. | All of the above |
| Answer» D. All of the above | |
| 209. |
The main function of under voltage protective device generally employed with a motor starter is to |
| A. | Open the supply circuit on failure of power supply |
| B. | Control the motor voltage |
| C. | Prevent the opening of supply circuit |
| D. | None of the above |
| Answer» A. Open the supply circuit on failure of power supply | |
| 210. |
The bias factor S in unit protection synchronous generators |
| A. | Lies between .05 and .1 pu |
| B. | Is less than .05 pu |
| C. | Lies between .1 to .25 pu |
| D. | Is greater than .025 pu |
| Answer» A. Lies between .05 and .1 pu | |
| 211. |
In a balanced voltage pilot wire protection scheme if the pilot circuit gets opened, the relay will |
| A. | Fail to trip on internal faults |
| B. | Trip on full load |
| C. | Trip instantaneously on external faults |
| D. | None of the above |
| Answer» A. Fail to trip on internal faults | |
| 212. |
In a balanced voltage pilot-wire protection scheme, if the pilot circuit gets shortcircuited, the relay will |
| A. | Fail to trip on internal faults |
| B. | Fail to trip on external faults |
| C. | Trip on full load |
| D. | Trip instantaneously |
| Answer» C. Trip on full load | |
| 213. |
The frequency of carrier in the carrier current pilot scheme is in the range of |
| A. | 1 kHz to 10 kHz |
| B. | 10 kHz to 25 kHz |
| C. | 25 kHz to 50 kHz |
| D. | 50 kHz to 500 kHz |
| Answer» D. 50 kHz to 500 kHz | |
| 214. |
The frequency of carrier transmitted by microwave pilot is in the range of |
| A. | 1000 kHz to 1500 kHz |
| B. | 2000 kHz to 5000 kHz |
| C. | 900 kHz to 6000 kHz |
| D. | 10000 kHz to 15000 kHz |
| Answer» C. 900 kHz to 6000 kHz | |
| 215. |
In carrier current protection the purpose of the wave trap is for |
| A. | Trapping power frequency waves |
| B. | Trapping high frequency waves entering into generators/ transformer unit |
| C. | Both a and b |
| D. | None of the above |
| Answer» B. Trapping high frequency waves entering into generators/ transformer unit | |
| 216. |
As soon as a fault develops in a generator stator, it is essential to suppress field excitation, otherwise |
| A. | Terminal voltage will drop |
| B. | It may lead to loss of synchronism |
| C. | It will continue to supply power to the stator winding fault |
| D. | All of the above |
| Answer» C. It will continue to supply power to the stator winding fault | |
| 217. |
Distance protection scheme is preferred over graded lime-lag over-current protection in HV and EHV lines because |
| A. | It is faster in operation |
| B. | It is simple |
| C. | It is cheaper in cost |
| D. | All of the above |
| Answer» A. It is faster in operation | |
| 218. |
Requirements of protection power station buildings against direct strokes are |
| A. | Interception |
| B. | Conduction |
| C. | . Dissipation |
| D. | All of the above |
| Answer» D. All of the above | |
| 219. |
The protection against direct lighting strokes and a high-voltage steep waves is provided by |
| A. | Ground wires |
| B. | Lightning arresters |
| C. | Lightning arresters and ground wires |
| D. | Earthing of neutral |
| Answer» C. Lightning arresters and ground wires | |
| 220. |
For protection of rotating machines against lightning surge .............is used |
| A. | Lightning arrester |
| B. | Capacitor |
| C. | Combination of lightning arrester and a capacitor |
| D. | Lightning conductor and arrester |
| Answer» C. Combination of lightning arrester and a capacitor | |
| 221. |
In between the generating station and consumers a number of transformation and switching stations exist, these are called the |
| A. | Switchgears |
| B. | Substations |
| C. | Intermediate substations |
| D. | Transformation stations |
| Answer» B. Substations | |
| 222. |
With large reactance interconnector between two power stations |
| A. | The power stations may fall out of step due to large angular displacement between the power stations |
| B. | Power will be transferred with minimum power losses |
| C. | Power will be transferred with voltage fluctuations and noise |
| D. | None of the above |
| Answer» A. The power stations may fall out of step due to large angular displacement between the power stations | |
| 223. |
In a isolated neutral system, when a single line to ground fault occurs |
| A. | Persistent arcing grounds will be developed |
| B. | Voltage in the healthy phases rise to full line value causing isolation breakdown |
| C. | The capacitive current in the faulty phase rises to 3 times its normal value |
| D. | All of the above |
| Answer» D. All of the above | |
| 224. |
Tap changing transformers are employed for |
| A. | Stepping down the voltage |
| B. | Stepping up the voltage |
| C. | Supplying low-voltage current to instruments |
| D. | Both stepping up and stepping down the voltage |
| Answer» D. Both stepping up and stepping down the voltage | |
| 225. |
Field failure in an alternator occurs due to |
| A. | Failure of exciter |
| B. | Faulty field circuit breaker |
| C. | In rush of large currents |
| D. | Both A and B |
| Answer» D. Both A and B | |
| 226. |
Large internal faults are protected by |
| A. | Merz price percentage differential protection |
| B. | Mho and ohm relays |
| C. | Horan gaps and temperature relays |
| D. | Earth fault and positive sequence relays |
| Answer» A. Merz price percentage differential protection | |
| 227. |
Which of the following is the least expensive protection for over current in lowvoltage system ? |
| A. | Rewireable fuse |
| B. | Isolator |
| C. | Oil circuit breaker |
| D. | Air break circuit breaker |
| Answer» A. Rewireable fuse | |
| 228. |
For the protection of power station buildings against direct strokes the requirements are |
| A. | Interception |
| B. | Interception and conduction |
| C. | Interception, conduction and dissipation |
| D. | Interception,conduction,dissipation and reflection |
| Answer» C. Interception, conduction and dissipation | |
| 229. |
The line insulation is............. the insulation level at the station equipment |
| A. | Less than |
| B. | Same as |
| C. | More than |
| D. | Not directly related with |
| Answer» D. Not directly related with | |
| 230. |
Short-circuit currents are due to |
| A. | Single phase to ground faults |
| B. | Phase to phase faults |
| C. | Three phase faults |
| D. | Any of these |
| Answer» D. Any of these | |
| 231. |
For which of the following protection from negative sequence current is provided? |
| A. | Generators |
| B. | Motors |
| C. | Transmission line |
| D. | Transformers |
| Answer» A. Generators | |
| 232. |
For which of the following ratings of the transformer differential protection is recommended? |
| A. | Above 30 KVA |
| B. | Equal to and above 5 MVA |
| C. | Equal two and above 25 MVA |
| D. | None of the above |
| Answer» B. Equal to and above 5 MVA | |
| 233. |
Over voltage protection is recommended for |
| A. | Hydro electric generators |
| B. | Steam turbine generators |
| C. | Gasturbine generators |
| D. | All of the above |
| Answer» D. All of the above | |
| 234. |
Overfluxing protection is recommended for |
| A. | Distribution transformer |
| B. | Generator transformer of the power plant |
| C. | Auto transformer of the power plant |
| D. | Station transformer of the power plant |
| Answer» B. Generator transformer of the power plant | |
| 235. |
Hey switchgear is device used for |
| A. | Interrupting an electrical circuit |
| B. | Switching an electrical circuit |
| C. | Reaching and controlling an electrical circuit |
| D. | Switching, controlling and protecting the electrical circuit and equipment |
| Answer» D. Switching, controlling and protecting the electrical circuit and equipment | |
| 236. |
Switching over voltage arc are more hazardous than lighting surges in case of |
| A. | Unbalanced systems |
| B. | Low-voltages |
| C. | 11 KV systems |
| D. | EHV and UHV systems |
| Answer» D. EHV and UHV systems | |
| 237. |
Least number of faults are generally reported for |
| A. | Transmission lines |
| B. | Cables |
| C. | Switchgears |
| D. | Transformers |
| Answer» B. Cables | |
| 238. |
Minimum working voltage will be least in case of |
| A. | Silver |
| B. | Graphite |
| C. | Carbon |
| D. | Tungsten |
| Answer» A. Silver | |
| 239. |
In a contactor, interrupting medium may be |
| A. | Air |
| B. | Oil |
| C. | Sf6 gas |
| D. | Any of the above |
| Answer» D. Any of the above | |
| 240. |
The transient voltages that appears across the contacts at the instant of arc extinction is called ..............voltage |
| A. | Supply |
| B. | Recovery |
| C. | Restriking |
| D. | Peak |
| Answer» C. Restriking | |
| 241. |
The power loss is an important factor for the design of |
| A. | Transmission line |
| B. | Motor |
| C. | Generator |
| D. | Feeder |
| Answer» B. Motor | |
| 242. |
SF6 gas |
| A. | Is yellow in colour |
| B. | Is lighter than air |
| C. | Is non-toxic |
| D. | Has pungent small |
| Answer» C. Is non-toxic | |
| 243. |
SF6 gas is transported in |
| A. | Air cylinders |
| B. | Gas cylinders |
| C. | Liquid from in cylinders |
| D. | Solid form in boxes |
| Answer» C. Liquid from in cylinders | |
| 244. |
The short-circuit in any winding of the transformer is the result of |
| A. | Mechanical vibration |
| B. | Insulation failure |
| C. | Loose connection |
| D. | Impulse voltage |
| Answer» D. Impulse voltage | |
| 245. |
The actuating quantity for the relays may be |
| A. | Magnitude |
| B. | Frequency |
| C. | Phase angle |
| D. | Any of the above |
| Answer» D. Any of the above | |
| 246. |
The operating speed of a relay depends upon the |
| A. | Rate of flux built up |
| B. | Armature core air gap |
| C. | Spring tension |
| D. | All of these |
| Answer» D. All of these | |
| 247. |
Inverse time current relays are used for the protection of |
| A. | Feeders |
| B. | Transformers |
| C. | Alternators |
| D. | Both A and B |
| Answer» D. Both A and B | |
| 248. |
IDMT relays are used to protect the power transformers against |
| A. | External short-circuit |
| B. | Over loads |
| C. | Internal short-circuits |
| D. | Both A and B |
| Answer» D. Both A and B | |
| 249. |
In distance protection, the relay measures |
| A. | Negative sequence impedance of the light from relay up to the fault point |
| B. | Positive sequence impedance of the line from relay up to the fault point |
| C. | Self impedance of the line from relay up to the fault point |
| D. | Zero sequence impedance of the line from relay up to the fault point |
| Answer» B. Positive sequence impedance of the line from relay up to the fault point | |
| 250. |
The relay used for phase fault protection of short transmission lines is |
| A. | Reactance relay |
| B. | Impedance relay |
| C. | Mho relay |
| D. | IDMT relay |
| Answer» A. Reactance relay | |
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