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Multiple Choice Question (MCQ) of Power Systems page-13


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141. The short circuit in any windings of the transformer is the result of

a) Impulse voltage
b) Insulation failure
c) Mechanical vibration
d) Magnetostriction force
e) Loose connection

Ans: (b)

142. Percentage differential protection in a transformer is recommended to prevent mal-operation due to

a) External fault currents
b) Internal fault currents
c) Magnetizing currents
d) None of the above

Ans: (c)

143. harmonic restraint in differential relay is provided so that the relay operates when harmonic current in transformer

a) Does not exceed 15% of fundamental
b) Exceed 15% of fundamental
c) Exceed 14.4% of fundamental
d) Exceed 17.3% of fundamental

Ans: (b)

144. The inverse definite mean time relays are used for over-current and earth fault protection of transformer against

a) External short circuits
b) Internal short circuits
c) Heavy overloads
d) All the above cases

Ans: (b)

145. Which of the following statement is true?

a) Shunt reactors are used for power factors improvement
b) Shunt reactor are used to control the line voltage
c) Shunt reactors are used to reduce the line impedance
d) Shunt reactors are used to eliminate line to ground capacitance

Ans: (a)

146. When a stator neutral of a generator is earthed through a distribution transformer, the stator earth fault is detected through

a) An over-voltage relay connected across the secondary of the transformer
b) An over-current relay connected across the secondary of the transformer
c) An under-voltage relay connected across the secondary of the transformer
d) None of the above

Ans: (a)

147. Split-phase relaying responds to faults between turns of a transformer.

a) True
b) False

Ans: (a)

148. A single ground fault in the field circuit of a large generator causes damage to the rotor.

a) True
b) False

Ans: (b)

149. Which of the following relays are used for phase fault on long line?

a) Impedance relays
b) Reactance relays
c) MHO relays
d) None of the above

Ans: (a)

150. For a detection of the occurrence of the severe synchronizing power surges

a) Impedance relays are best suited
b) MHO relays best suited
c) Reactance relays are best suited
d) Split-phase relays are best suited

Ans: (b)


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