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UNIT-I

1. Under no load conditions the current in a transmission line is due to.

a) Corona effects

b) Capacitance of the linec) Back flow from earth

d)None of the aboveAns: (b)

2. In the short transmission line which of the following is neglected?

a) I2 R loss

b) Shunt admittance

c) Series impedance

d) All of the aboveAns: (b)

3. Which of the following loss in a transformer is zero even at full load?

a) Eddy current

b) Hysteresis

c) Core loss

d) Friction lossAns: (d)

4. The transmission line conductors are transposed to

a) Balance the current

b) Obtain different losses

c) Obtain same line dropsd) Balance the voltageAns: (c)

5. When a 1-phase supply is across a 1-phase winding, the nature of the

magnetic field produced is

a) Constant in magnitude and direction

b) Constant in magnitude and rotating at synchronous speed

c) Pulsating in nature

d) Rotating in natureAns: (c)

6. The damper windings are used in alternators to

a) Reduce eddy current loss

b) Reduce hunting

c) Make rotor dynamically balanced

d) Reduce armature reactionAns: (b)

7. The neutral path impedance Zn is used in the equivalent sequence network

models as

a) Zn2

b) Zn

c) 3 Zn

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d) An ineffective valueAns: (c)8. An infinite bus-bar should maintain

a) Constant frequency and Constant voltage

b) Infinite frequency and Infinite voltage

c) Constant frequency and Variable voltaged) Variable frequency and Variable voltageAns: (a)9. Voltages under extra high voltage are

a) 1KV & above

b) 11KV & above

c) 132 KV & above

d) 330 KV & aboveAns: (d)10. If a positive sequence current passes through a transformer and its phase shift is 30

degrees, the negative sequence current flowing through the transformer will have a phase

shift ofa) 30 deg.

b) -30deg

c) 120 deg.

d) 180 deg.

Ans: (b)

11. The zero sequence impedances of an ideal star-delta connected transformer (star-

grounded)

a) looking from star side is zero and looking from delta side is infinite

b) looking from star side is zero and looking from delta side is also zero

c) looking from star side is infinite and looking from delta side is zero

d)None of above

Ans: (a)

12. The positive, negative and zero sequence impedances of a transmission line are 0.5,0.5

and 1.1 pu respectively. The self (Zs) and mutual (Zm) impedances of the line will be given

by

a)Zs = 0.7 pu, Zm =0.2 pu

b)Zs = 0.5 pu, Zm =0.6 pu

c)Zs = 1 pu, Zm =0.6 pu

d)Zs = 1 pu, Zm =0.5 puAns: (a)

13. Symmetrical component method of analysis is more useful when

a) system has unsymmetrical fault and the network is otherwise balanced

b) system has symmetrical fault and the network is otherwise unbalanced

c) system has unsymmetrical fault and the network is unbalanced

Ans: (a)

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14.For a line to line fault analysis using symmetrical components,

a)The positive and negative sequence networks at the fault point are connected in series

b)The positive and negative sequence networks at the fault point are connected in parallel

c)The positive, negative, and zero sequence networks at the fault point are connected in

parallel

Ans: (b)

15. The synchronous reactance of a modern large size turbo-generator in pu is nearest to

a) 1

b) 2

c) 3

d) 4

Ans: (b)

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