Testing And Commissioning Of Electrical Equipment’S Set 9
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This set of Testing and Commissioning of Electrical Equipment’s Multiple Choice Questions & Answers (MCQs) focuses on Testing And Commissioning Of Electrical Equipment’S Set 9
Q1 | For the protection of a large squirrel cage induction motor against single phasenormally
- An over-current relay is used
- Differential relay is used
- Directional relay is used
- Negative sequence current sensitive relay is used
Q2 | The most commonly used method for the protection of three phase feeder is
- Time graded protection
- Differential protection
- Reverse power protection
- None of the above
Q3 | Which is the pilotless protection method for feeder line ?
- Differential protection
- Carrier current protection
- Time credit protection
- None of the above
Q4 | Time graded protection of a radial feeder can be achieved by using
- Definite time relay
- Inverse time relay
- Both definite and inverse time relays
- None of the above
Q5 | Pilot-wire protection scheme is the most economical and provides high speedrelaying for
- Short length of lines upto 15 km
- Medium length of lives up to 60 km
- Long length of lines up to 200 km
- All of the above
Q6 | Problems associated with differential protection is/are
- Magnetising inrush current
- Mismatching characteristics of CTs
- Charge of ratio as a result of tapping
- All of the above
Q7 | For the protection of transformers, harmonic restraint is used to guard against
- Magnetising inrush current
- Unbalanced operation
- Lightning
- Switching over-voltage
Q8 | The types of faults that occur in electric motors are
- Stator
- Rotor
- Overload
- All of the above
Q9 | The main function of under voltage protective device generally employed with amotor starter is to
- Open the supply circuit on failure of power supply
- Control the motor voltage
- Prevent the opening of supply circuit
- None of the above
Q10 | The bias factor S in unit protection synchronous generators
- Lies between .05 and .1 pu
- Is less than .05 pu
- Lies between .1 to .25 pu
- Is greater than .025 pu
Q11 | In a balanced voltage pilot wire protection scheme if the pilot circuit gets opened,the relay will
- Fail to trip on internal faults
- Trip on full load
- Trip instantaneously on external faults
- None of the above
Q12 | In a balanced voltage pilot-wire protection scheme, if the pilot circuit gets shortcircuited, the relay will
- Fail to trip on internal faults
- Fail to trip on external faults
- Trip on full load
- Trip instantaneously
Q13 | The frequency of carrier in the carrier current pilot scheme is in the range of
- 1 kHz to 10 kHz
- 10 kHz to 25 kHz
- 25 kHz to 50 kHz
- 50 kHz to 500 kHz
Q14 | The frequency of carrier transmitted by microwave pilot is in the range of
- 1000 kHz to 1500 kHz
- 2000 kHz to 5000 kHz
- 900 kHz to 6000 kHz
- 10000 kHz to 15000 kHz
Q15 | In carrier current protection the purpose of the wave trap is for
- Trapping power frequency waves
- Trapping high frequency waves entering into generators/ transformer unit
- Both a and b
- None of the above
Q16 | As soon as a fault develops in a generator stator, it is essential to suppress field excitation, otherwise
- Terminal voltage will drop
- It may lead to loss of synchronism
- It will continue to supply power to the stator winding fault
- All of the above
Q17 | Distance protection scheme is preferred over graded lime-lag over-current protection in HV and EHV lines because
- It is faster in operation
- It is simple
- It is cheaper in cost
- All of the above
Q18 | Requirements of protection power station buildings against direct strokes are
- Interception
- Conduction
- . Dissipation
- All of the above
Q19 | The protection against direct lighting strokes and a high-voltage steep waves isprovided by
- Ground wires
- Lightning arresters
- Lightning arresters and ground wires
- Earthing of neutral
Q20 | For protection of rotating machines against lightning surge .............is used
- Lightning arrester
- Capacitor
- Combination of lightning arrester and a capacitor
- Lightning conductor and arrester
Q21 | In between the generating station and consumers a number of transformation andswitching stations exist, these are called the
- Switchgears
- Substations
- Intermediate substations
- Transformation stations
Q22 | With large reactance interconnector between two power stations
- The power stations may fall out of step due to large angular displacement between the power stations
- Power will be transferred with minimum power losses
- Power will be transferred with voltage fluctuations and noise
- None of the above
Q23 | In a isolated neutral system, when a single line to ground fault occurs
- Persistent arcing grounds will be developed
- Voltage in the healthy phases rise to full line value causing isolation breakdown
- The capacitive current in the faulty phase rises to 3 times its normal value
- All of the above
Q24 | Tap changing transformers are employed for
- Stepping down the voltage
- Stepping up the voltage
- Supplying low-voltage current to instruments
- Both stepping up and stepping down the voltage
Q25 | Field failure in an alternator occurs due to
- Failure of exciter
- Faulty field circuit breaker
- In rush of large currents
- Both A and B