Top 250+ Solved Testing and Commissioning of Electrical Equipment’s MCQ Questions Answer
Q. 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
Q. 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
Q. 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
Q. Pilot-wire protection scheme is the most economical and provides high speedrelaying 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
Q. 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
Q. 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
Q. The types of faults that occur in electric motors are
a. Stator
b. Rotor
c. Overload
d. All of the above
Q. The main function of under voltage protective device generally employed with amotor 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
Q. 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
Q. 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
Q. 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
Q. 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
Q. 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
Q. 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
Q. 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