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Multiple Choice Question (MCQ) of Power Systems page-12


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131. For which of the following ratings of the transformer differential protection is recommended

a) Above 50 kV
b) Equal to and above 5 MVA
c) Equal to and above 20 MVA
d) Either of the above cases

Ans: (b)

132. When the stator neutral of a generator is grounded through a resistor, the stator ground fault is detected through

a) An under-voltage relay connected across the resistor
b) An over-voltage relay connected across the resistor
c) An over-current relay connected to the current CT
d) Any ground fault relay

Ans: (c)

133. The longitudinal differential relaying system responds in faults between turns of winding of a transformer.

a) True
b) False

Ans: (a)

134. Over voltage protection is recommended for

a) Steam turbine generators
b) Hydro-electric generators
c) Gas turbine generators
d) All the above
e) None of the above

Ans: (d)

135. Distance relays are generally

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

Ans: (a)

136. Which of the following relay is preferred for phase fault on short transmission line

a) Reactance relay
b) Impedance relay
c) MHO relay
d) Induction type relay

Ans: (a)

137. In case of multi-terminal line the first zero of the distance relay is set to reach 80 to 90%of the distance from the nearest terminal.

a) True
b) False

Ans: (a)

138. The knee-point in the magnetizing characteristics of a CT is a point where 10% increase in the secondary voltage increases

a) The exciting current by 10%
b) The exciting current by 30%
c) The exciting current by 50%
d) The exciting current by 14.4%
e) The primary voltage by 10%

Ans: (c)

139. Fuses are used where relays and circuit breakers

a) Fail to interrupt heavy short circuit currents
b) Are not economically justified
c) Are not available
d) Require more care and maintenance
e) Take more time to clear the fault

Ans: (b)

140. The impedance relay does not have directional features.

a) True
b) False

Ans: (a)


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