MCQOPTIONS
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MCQOPTIONS
This section includes 1267 Mcqs, each offering curated multiple-choice questions to sharpen your Embedded Systems knowledge and support exam preparation. Choose a topic below to get started.
| 101. |
The inverse definite mean time relays are used for over current and earth faultprotection of transformer against |
| A. | Heavy loads |
| B. | Internal short circuits |
| C. | External short circuits |
| D. | All of the above |
| Answer» C. External short circuits | |
| 102. |
The heat produced at the contact point owing to flow of electric current is leastaffected by_____________________. |
| A. | Temperature of the surrounding medium. |
| B. | Contact resistance. |
| C. | Magnitude of electric current flowing. |
| D. | Duration of flow of current. |
| Answer» B. Contact resistance. | |
| 103. |
SF6 gas is imported in _____________. |
| A. | Air cylinders |
| B. | Gas cylinders |
| C. | Liquid form in cylinders |
| D. | Solid form. |
| Answer» D. Solid form. | |
| 104. |
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» D. Many turns of thick wire | |
| 105. |
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» E. | |
| 106. |
A differential relay measures the vector differencebetween |
| A. | two currents |
| B. | two voltages |
| C. | two or more similar electrical quantities |
| D. | none of the above |
| Answer» D. none of the above | |
| 107. |
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» E. | |
| 108. |
The voltage appearing across the contacts after opening of the circuit breaker iscalled______voltage. |
| A. | recovery |
| B. | surge |
| C. | operating |
| D. | arc |
| Answer» B. surge | |
| 109. |
In between the generating station and consumers a number of transformation andswitching stations exist, these are called the |
| A. | Switchgears |
| B. | Substations |
| C. | Intermediate substations |
| D. | Transformation stations |
| Answer» C. Intermediate substations | |
| 110. |
During arc extinction SF6 gas gets converted to which among these? |
| A. | Gets decomposed to SF4 and SF2 |
| B. | Gets decomposed to S and F |
| C. | Gets reduced to SF6 |
| D. | Gets oxidized |
| Answer» B. Gets decomposed to S and F | |
| 111. |
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» E. | |
| 112. |
What is the interrupting medium in the contactor? |
| A. | Air at atmospheric pressure. |
| B. | SF6 gas |
| C. | Oil |
| D. | All of the above. |
| Answer» E. | |
| 113. |
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» C. Both a and b | |
| 114. |
What does protective relay provide? |
| A. | Provide additional safety to the circuit breaker in its operation. |
| B. | Close the contacts when the actuating quantity attains a certain predetermined value. |
| C. | Limit the arcing current during the circuit breaker operation. |
| D. | Earth or ground any stray voltage. |
| Answer» C. Limit the arcing current during the circuit breaker operation. | |
| 115. |
What is the typical value of the pre arcing time? |
| A. | 0.1 |
| B. | 0.01 |
| C. | 0.001 |
| D. | 0.0001 |
| Answer» D. 0.0001 | |
| 116. |
What is the making to breaking current ratio for an extra high voltage circuit breaker? |
| A. | More than 1 |
| B. | Equal to 1 |
| C. | Less than 1 |
| D. | A negative value |
| Answer» B. Equal to 1 | |
| 117. |
When using air blast circuit breaker, current chopping is a phenomenon observedwhen |
| 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» D. A heavy load is switched off. | |
| 118. |
The actuating quantity for the relays may be |
| A. | Magnitude |
| B. | Frequency |
| C. | Phase angle |
| D. | Any of the above |
| Answer» E. | |
| 119. |
For which of the following ratings of the transformer differential protection isrecommended? |
| A. | Above 30 KVA |
| B. | Equal to and above 5 MVA |
| C. | Equal two and above 25 MVA |
| D. | None of the above |
| Answer» C. Equal two and above 25 MVA | |
| 120. |
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» D. Only up to 1100 KV | |
| 121. |
Which among these is the least expensive protection for over current in lowvoltage system? |
| A. | Rewirable fuse. |
| B. | Isolator. |
| C. | Circuit breaker. |
| D. | Air breaker switch. |
| Answer» B. Isolator. | |
| 122. |
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» B. The ratio of minimum fusing current to the current rating of the fuse | |
| 123. |
Why are the isolators used? |
| A. | Break abnormal current |
| B. | Making under fault conditions |
| C. | Breaking the circuit under no load condition |
| D. | None of the above |
| Answer» D. None of the above | |
| 124. |
The operating characteristics of the reactance relay in the complex impedanceplane 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» E. | |
| 125. |
The domains of power system where directional over current relay is indispensableare |
| 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» D. None of the above | |
| 126. |
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» E. | |
| 127. |
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» C. Straight line passing through origin | |
| 128. |
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» D. Trip instantaneously | |
| 129. |
What is the average rate of rise of restriking voltage upto the first peak? |
| A. | 525 * 103kV / sec |
| B. | 453 * 103kV / sec |
| C. | 582 * 103 kV / sec |
| D. | 467 * 103 kV / sec |
| Answer» C. 582 * 103 kV / sec | |
| 130. |
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» B. Nondirectional relay at both ends | |
| 131. |
In a circuit breaker the contact space is ionised by what? |
| A. | Field emission from the contact surface. |
| B. | Thermal emission from the contact surface. |
| C. | Thermal ionisation of gas. |
| D. | All of above. |
| Answer» D. All of above. | |
| 132. |
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» D. None of these. | |
| 133. |
The rating of the circuit breaker is usually determined on the basis of ____________ fault. |
| A. | Symmetrical |
| B. | Line to line |
| C. | Single line to ground |
| D. | Double line to ground |
| Answer» B. Line to line | |
| 134. |
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» E. | |
| 135. |
By using low resistance method for arc extension what is the value of arcresistance? |
| A. | Arc resistance is zero. |
| B. | Arc resistance is high |
| C. | Arc resistance is low |
| D. | Arc resistance is very high |
| Answer» D. Arc resistance is very high | |
| 136. |
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» E. | |
| 137. |
Impedance relay may use |
| A. | Balance beam structure |
| B. | Induction cup structure |
| C. | Shaded pole structure |
| D. | Either A or B |
| Answer» E. | |
| 138. |
To protect most of the electrical equipment handling low power, the types of relaysused are |
| A. | Thermocouple |
| B. | Electronic and bimetallic |
| C. | Both A and B |
| D. | None of the above |
| Answer» D. None of the above | |
| 139. |
Which circuit breaker is preferred to be installed in extra high voltage ACsystem? |
| A. | Bulk oil type circuit breaker |
| B. | Air blast circuit breaker |
| C. | SF6 circuit breaker |
| D. | Vacuum circuit breaker |
| Answer» D. Vacuum circuit breaker | |
| 140. |
The relay used for feeder protection is |
| A. | Under voltage relay |
| B. | Translay relay |
| C. | Thermal relay |
| D. | Buchholz relay |
| Answer» C. Thermal relay | |
| 141. |
The stability of arc in vacuum depends on _________. |
| A. | The contact material only. |
| B. | The circuit parameters only. |
| C. | The contact materials and its vapour pressure. |
| D. | Both (b) and (c) |
| Answer» E. | |
| 142. |
Which of the following circuit breaker is highly reliable and has a least maintenance? |
| A. | Oil circuit breakers |
| B. | Air blast |
| C. | Vacuum circuit breakers |
| D. | SF6 circuit breakers |
| Answer» E. | |
| 143. |
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» B. Isolator | |
| 144. |
Refer to the following facts to answer the question A 50 Hz, 11 kV, 3 phase alternator 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 upto CB between the phase and neutral is 0.01 μ F. What is the frequency of oscillations? |
| A. | 10000 Hz |
| B. | 12500 Hz |
| C. | 12628 Hz |
| D. | 13265 Hz |
| Answer» D. 13265 Hz | |
| 145. |
Arcing voltage will be the least in case of |
| A. | Carbon |
| B. | Copper |
| C. | Silver |
| D. | Tungsten |
| Answer» D. Tungsten | |
| 146. |
The isolators used in the transmission lines are capable of breaking |
| A. | Fault current |
| B. | No current |
| C. | Charging current |
| D. | Load current |
| Answer» D. Load current | |
| 147. |
In order that current should flow without causing excessive heating or voltagedrop, 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» E. | |
| 148. |
The structure used in reactance relay is |
| A. | Induction cup |
| B. | Double induction loop |
| C. | Single induction loop |
| D. | Either A or B |
| Answer» E. | |
| 149. |
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» D. Lightning conductor and arrester | |
| 150. |
The delay fuses are used for the protection of ________. |
| A. | motors |
| B. | power outlet circuits |
| C. | fluorescent lamps |
| D. | light circuits |
| Answer» B. power outlet circuits | |