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Multiple Choice Question (MCQ) of C. Power System Protection page-3


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21. If the time of operating of a relay for unity TMS is 10secs., the time of operation for 0.5 TMS will be

a) 20 secs.
b) 5 secs.
c) 10 secs.
d) None of the above

Ans: (b)

22. If the phase angle of the voltage coil of a directional relay is 50° the maximum torque angle of the relay is

a) 130°
b) 100°
c) 25°
d) None of the above

Ans: (d)

23. A fault is more severe from the view point of RRRV if is a

a) Short line fault.
b) Medium length line fault.
c) Long line fault.
d) None of these.

Ans: (a)

24. A reactance relay is

a) Voltage restrained directional relay.
b) Directional restrained over-current relay.
c) Voltage restrained over-current relay.
d) None of the above.

Ans: (b)

25. For measuring positive, negative and zero sequence voltages in a system, the reference is taken as

a) Neutral of the system only.
b) Ground only.
c) For zero sequence neutral and for positive and negative the ground.
d) None of the above.

Ans: (d)

26. Positive, negative and zero sequence impedances of a solidly grounded system under steady state condition always follow the relations

a) Z4>Z2>Z0
b) Z2>Z4>Z0
c) Z0>Z4>Z2
d) None of the above

Ans: (a)

27. Phase comparators in case of static relays and electro-mechanical relays normally are

a) Sine and cosine comparators respectively
b) Cosine and sine comparators respectively.
c) Both are cosine comparators.
d) Both are sing comparators.

Ans: (b)

28. For reducing tower footing resistance it is better to use

a) Chemical and ground rods only.
b) Chemical and counterpoise only.
c) Ground rod and counterpoise only.
d) Chemical, ground rods and counterpoise.

Ans: (c)

29. Rate of rise of restriking voltage depends

a) Type of circuit breaker.
b) Inductance of the system only.
c) Capacitance of the system only.
d) Inductance and capacitance of the system

Ans: (d)

30. Breakdown strength of air at STP is 24 kV/cm. Its breakdown strength at 30°C and 72 cm of Hg will be

a) 24.25 kV/cm.
b) 20.2 kV/cm.
c) 23 kV.
d) 49.5 kV/cm.

Ans: (d)


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