page 8 | Power Systems Multiple Choice Questions

Q81. Fuse is used for the following purpose

Overload protection

Short circuit protection

Used up to 66 kV

All of the above

Q82. The components used in the output circuit of static relay is

OP-AMP

Comparator

Capacitor

Thyristor

Q83. If the fault current is 4000 A, the C.T. ratio is 400/5 and the relay plug setting is 100%, the plug setting multiplier will be

20

40

10

15

Q84. Bimetallic strip present in Thermal relays will have two metal strips having different

Coefficient of expansion

Thermal Conductivity

Specific heat

all

Q85. Induction cup relay is operated due to changes in

Current

Voltage

Impedance

all of above

Q86. The operating time of an inverse definite minimum time (IDMT) overcurrent relay corresponding to plug-setting multiplier (PSM) = 1 and time-multiplier setting (TMS) = 1 will be

zero

3 sec

infinite

1 sec

Q87. The impedance relay is used for protection of

transformer.

bus-bar.

synchronous generator.

transmission line.

Q88. If a fault occurs near the relay, the V/I ratio will be

Lower than that if the fault occurs away from the relay.

Higher than that if the fault occurs away from the relay.

Constant for all distances.

Will be initially constant and then increase.

Q89. The purpose of the restraining coil in a biased differential relay is

To reduce CT saturation during fault.

To increase the sensitivity of the relay.

To match the transformation ratio.

To limit the spill current through the relay during heavy external fault.

Q90. A 50 \(Hz\), 3-phase synchronous generator has inductance per phase of 15 mH. The capacitance of generator and circuit breaker is \(0.002\mu\)F. What is its natural frequency of oscillation?

29\(kHz\)

2.9\(kHz\)

290\(kHz\)

29\(MHz\)

MCQ

POWER SYSTEM