Multiple Choice Questions in Power Systems - 1

Important multiple choice questions in Power systems

1.       In pump storage hydropower plant, the electrical machine is made to work alternately as generator and motor. The efficiency of the generator working at the same electrical power level is

A)     Greater than that as motor

B)      Equal to that as motor

C)      Less than that as motor

D)     Greater or less than that as motor depending on the type of machine

2.       In a thermal nuclear reactor

                                I.            The purpose of moderator is to slowdown fast neutrons produced due to fusion.

                              II.            The moderator material must have low molecular weight.

                            III.            Ordinary water can be used as moderator with natural uranium as fuel.

                            IV.            The multiplication factor is kept slightly greater than unity during its normal functioning.

Which of these statements are correct?

A)     1 and 3

B)      3 and 4

C)      1,2 and 3

D)     1,2 and 4

3.       Consider the following statements:

Surge impedance loading of a transmission line can be increased by

                                I.            Increasing its voltage level

                              II.            Addition of lumped inductance in parallel

                            III.            Addition of lumped capacitance in series

                            IV.            Reducing the length of line

Which of these statements are correct?

A)     1 and 3

B)      1 and 4

C)      2 and 4

D)     3 and 4

4.       The load current in short circuit calculation are neglected because

                                I.            Short circuit currents are much larger than load currents

                              II.            Short circuit currents are greatly out of phase with load currents

Which of these statements is/are correct?

A)     Neither 1 nor 2

B)      2 alone

C)      1 alone

D)     1 and 2

5.       The surge impedance of a 3 phase, 400kV transmission line is 400Ω. The surge impedance loading (SIL) is

A)     400 MW

B)      100 MW

C)      1600 MW

D)     200 MW

6.       If a travelling-wave travelling along a loss-free overhead line does not result in any reflection after it has reached the far end, then the far end of the line

A)     Open circuited

B)      Short circuited

C)      Terminated in to a resistance equal to surge impedance of the line

D)     Terminated in to a capacitor

7.       A travelling wave 400/1/50 means crest value of

A)     400 V with rise time 1/50 S

B)      400 kV with rise time 1 S and fall time 50S

C)      400 kV with rise time 1 µS with fall time 50µS

D)     400MV with rise time 1µS and fall time 50µS

8.       Installation of capacitors at suitable locations and of optimum size in a distribution system results in

                                                        I.            Improved voltage regulation.

                                                      II.            Reduction in distribution power losses.

                                                    III.            Reduction of KVA rating of distribution transformers.

Select the correct answer using codes given below:

A)     1 alone

B)      1 and 2

C)      1,2 and 3

D)     3 alone

9.       In a three unit insulator string, voltage across the lowest unit is 17.5kV and string efficiency is 84.28%. the total voltage across the string will be equal to

A)     8.825 kV

B)      44.25 kV

C)      88.25 kV

D)     442.5 kV

10.   Bundled conductors are used for EHV transmission lines primarily for reducing the

A)     Corona loss

B)      Surge impedance of the line

C)      Voltage drop across the line

D)     Copper loss