McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering .
| 251. |
Where severe synchronising swing occur, the relay employed is |
| A. | Impedance relay |
| B. | Mho relay |
| C. | Reactance relay |
| D. | Induction relay |
| Answer» B. Mho relay | |
| 252. |
For the protection of lines against faults involving variable fault resistance, the preferred relaying scheme is a |
| A. | Plain impedance relay |
| B. | Directional over-current relay |
| C. | Mho relay |
| D. | Reactance relay |
| Answer» D. Reactance relay | |
| 253. |
For ground fault we prefer |
| A. | Plain impedance relay |
| B. | Directional over current relay |
| C. | Mho relay |
| D. | Reactance relay |
| Answer» D. Reactance relay | |
| 254. |
Admittance relay |
| A. | Nondirectional relay |
| B. | Directional relay |
| C. | Differential relay |
| D. | None of the above |
| Answer» B. Directional relay | |
| 255. |
The relay used for feeder protection is |
| A. | Under voltage relay |
| B. | Translay relay |
| C. | Thermal relay |
| D. | Buchholz relay |
| Answer» B. Translay relay | |
| 256. |
Which relay is used to detect and protect internal fault in a transformer ? |
| A. | Buchholz relay |
| B. | Directional relay |
| C. | Thermal relay |
| D. | Distance relay |
| Answer» A. Buchholz relay | |
| 257. |
Which one of the following relay has the capability of anticipating the possible major fault in a transformer ? |
| A. | Over-current relay |
| B. | Differential relay |
| C. | Buchholz relay |
| D. | Over fluxing relay |
| Answer» C. Buchholz relay | |
| 258. |
Zero sequence current is used for relaying purpose only in the case of |
| A. | Phase over current really |
| B. | Phase impedance relay |
| C. | Ground over current relay |
| D. | Ground impedance relay |
| Answer» C. Ground over current relay | |
| 259. |
To prevent mal operation of differentially connected relay while energising a transformer, the relay restraining coil is biased with |
| A. | Second harmonic current |
| B. | Third harmonic current |
| C. | Fifth harmonic current |
| D. | Seventh harmonic current |
| Answer» A. Second harmonic current | |
| 260. |
How many relays are used to detect interphase fault of a three line system? |
| A. | One |
| B. | Two |
| C. | Three |
| D. | Six |
| Answer» C. Three | |
| 261. |
Which is the main relay for protecting up to 90% of the transmission line-length in the forward direction? |
| A. | Directional over current relay |
| B. | Mho relay |
| C. | Carrier current protective relay |
| D. | Impedance relay |
| Answer» B. Mho relay | |
| 262. |
For protection of parallel feeders fed from one end, the relays required are |
| A. | Nondirectional relays at the source end and directional relay at the load end |
| B. | Nondirectional relay at both ends |
| C. | Directional relay at source end and nondirectional relay at load end |
| D. | Directional relay at both ends |
| Answer» A. Nondirectional relays at the source end and directional relay at the load end | |
| 263. |
Relays can be designed to respond to changes in |
| A. | Resistance, reactance or impedance |
| B. | Voltage and current |
| C. | Light intensity |
| D. | All of the above |
| Answer» D. All of the above | |
| 264. |
DC shunt relays are made of |
| A. | Few turns of thin wire |
| B. | Few turns of thick wire |
| C. | Many turns of thin wire |
| D. | Many turns of thick wire |
| Answer» C. Many turns of thin wire | |
| 265. |
In order that current should flow without causing excessive heating or voltage drop, the relay contacts should |
| A. | Have low contact resistance |
| B. | Be clean and smooth |
| C. | Be of sufficient size and proper shape |
| D. | Have all above properties |
| Answer» D. Have all above properties | |
| 266. |
Interruption of large currents by relay requires |
| A. | Arc suppressing blow out coils |
| B. | Wide separation of the open contacts |
| C. | High speed opening of contacts |
| D. | All of the above |
| Answer» D. All of the above | |
| 267. |
To protect most of the electrical equipment handling low power, the types of relays used are |
| A. | Thermocouple |
| B. | Electronic and bimetallic |
| C. | Both A and B |
| D. | None of the above |
| Answer» C. Both A and B | |
| 268. |
............. Relays are used for phase faults on long line |
| A. | Impedance |
| B. | Reactance |
| C. | Either of the above |
| D. | None of the above |
| Answer» A. Impedance | |
| 269. |
........ Relays is preferred for phase fault on short transmission line |
| A. | Induction type |
| B. | Reactance |
| C. | Impedance |
| D. | None of the above |
| Answer» B. Reactance | |
| 270. |
The under voltage relay can be used for |
| A. | Generators |
| B. | Bus bars |
| C. | Transformers |
| D. | All of the above |
| Answer» D. All of the above | |
| 271. |
The single phasing relays are used for the protection of |
| A. | Single phase motors only |
| B. | Two phase motors only |
| C. | Two single phase motor running in parallel |
| D. | Three phase motors |
| Answer» D. Three phase motors | |
| 272. |
The inverse definite mean time relays are used for over current and earth fault protection of transformer against |
| A. | Heavy loads |
| B. | Internal short circuits |
| C. | External short circuits |
| D. | All of the above |
| Answer» B. Internal short circuits | |
| 273. |
In a static over current relay, inverse time characteristics are obtained by |
| A. | A transistor amplifier |
| B. | An integrating circuit |
| C. | A transistor switch |
| D. | A differentiating circuit |
| Answer» B. An integrating circuit | |
| 274. |
In the case of transmission line protection, over current relay is used |
| A. | Only up to 110 KV |
| B. | Only up to 220 KV |
| C. | Only up to 50 KV |
| D. | Only up to 1100 KV |
| Answer» C. Only up to 50 KV | |
| 275. |
Directional over current relays have two exciting coils connected across |
| A. | CT secondaries of two different phases |
| B. | VT secondaries of two different phases |
| C. | CT and VT secondaries of same phases |
| D. | CT and VT secondaries of two different phases |
| Answer» C. CT and VT secondaries of same phases | |
| 276. |
The domains of power system where directional over current relay is indispensable are |
| A. | In case of parallel feeder protection |
| B. | In case of ring main feeder protection |
| C. | Both A and B |
| D. | None of the above |
| Answer» C. Both A and B | |
| 277. |
In an inverse definite minimum time, electromagnetic type over current relay, the minimum time feature is achieved because of |
| A. | Saturation of the magnetic circuit |
| B. | Proper mechanical design |
| C. | Appropriate time delay element |
| D. | Electromagnetic damping |
| Answer» A. Saturation of the magnetic circuit | |
| 278. |
Impedance relay can be used for |
| A. | Phase faults only |
| B. | Earth faults only |
| C. | Both earth and phase faults |
| D. | None of the above |
| Answer» A. Phase faults only | |
| 279. |
Impedance relay may use |
| A. | Balance beam structure |
| B. | Induction cup structure |
| C. | Shaded pole structure |
| D. | Either A or B |
| Answer» D. Either A or B | |
| 280. |
An impedance is relay is a |
| A. | Voltage restrained over current relay |
| B. | Voltage restrained directional relay |
| C. | Directional restrained over current relay |
| D. | Directional restrained over voltage relay |
| Answer» A. Voltage restrained over current relay | |
| 281. |
On transient fault OC and impedance relay |
| A. | Under reaches |
| B. | Over reaches |
| C. | Reach unaffected |
| D. | None of the above |
| Answer» A. Under reaches | |
| 282. |
Threshold characteristics of a plain impedance relay in a complex Z plane is a |
| A. | Circle passing through origin |
| B. | Circle with the centre at the origin |
| C. | Straight line passing through origin |
| D. | Straight line offset from the origin |
| Answer» B. Circle with the centre at the origin | |
| 283. |
The structure used in reactance relay is |
| A. | Induction cup |
| B. | Double induction loop |
| C. | Single induction loop |
| D. | Either A or B |
| Answer» D. Either A or B | |
| 284. |
Reactance relay is normally used for protection against |
| A. | Earth fault only |
| B. | Phase fault only |
| C. | Both earth and phase faults |
| D. | None of the above |
| Answer» A. Earth fault only | |
| 285. |
The operating characteristics of the reactance relay in the complex impedance plane is a |
| A. | Circle with its origin at the centre of the R-X plane |
| B. | Circle passing through the origin |
| C. | Straight line passing through the origin |
| D. | Straight line parallel to the X axis |
| Answer» D. Straight line parallel to the X axis | |
| 286. |
A reactance relay is |
| A. | Voltage restrained overcurrent relay |
| B. | Voltage restrained directional relay |
| C. | Directional restrained overcurrent relay |
| D. | Directional restrained over voltage relay |
| Answer» C. Directional restrained overcurrent relay | |
| 287. |
Reactance relays are used for phase fault in.......line |
| A. | Short |
| B. | Medium |
| C. | Long |
| D. | All of the above |
| Answer» A. Short | |
| 288. |
A differential relay response to |
| A. | Algebraic difference of two or more similar electrical quantities |
| B. | Phasor difference of two or more similar electrical quantities |
| C. | Algebraic difference between two currents |
| D. | Algebraic difference between two voltages |
| Answer» B. Phasor difference of two or more similar electrical quantities | |
| 289. |
Differential relays are used for protection of |
| A. | Feeders |
| B. | Alternators |
| C. | Transformers |
| D. | All of the above |
| Answer» D. All of the above | |
| 290. |
Differential relays are used for protection of equipments against |
| A. | Internal faults |
| B. | Over current |
| C. | Reverse current |
| D. | Reverse power |
| Answer» A. Internal faults | |
| 291. |
In a biased differential relay the bias is defined as a ratio of |
| A. | Number of turns of restraining and operating coil |
| B. | Operating coil current and restraining coil current |
| C. | Fault current and operating coil current |
| D. | Fault current and restraining coil current |
| Answer» B. Operating coil current and restraining coil current | |
| 292. |
Both voltage and current signals are required for |
| A. | A plain over current relay |
| B. | A differential relay |
| C. | A directional relay |
| D. | A biased directional relay |
| Answer» C. A directional relay | |
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