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