## electrical

### Transmission and Distribution MCQ Objective Questions and Answers Page - 4

1.
 Which of the following is neglected while analysing a short transmission line  ? A Shunt admittances. B Power losses. C Series impedance. D None the above. Answer : A Explanation :
2.
 In modelling the equivalent circuit of a short length overhead transmission line, the line resistance and inductance are only considered because line capacitance to ground is A Equal to zero B Finite but very small C Finite but very large D Infinite Answer : B Explanation :
3.
 Which of the following voltage regulation is considered to be the test  ? A 2% B 30% C 70% D 98% Answer : A Explanation :
4.
 If in a short transmission line, resistance and inductive reactance are found to be equal and regulation appears to be zero, then the load will A Have unity power factor B Have zero power factor C Be 0.707 leading D Be 0.707 lagging Answer : C Explanation :
5.
 For a short line if the receiving-end voltage is equal to sending-end voltage under loaded conditions A The sending-end power factor is unity. B The receiving-end power factor is unity. C The sending-end power factor is leading. D The receiving-end power factor is leading. Answer : D Explanation :
6.
 For an ac transmission line of length not exceeding 80 km, it is usual to lump the line capacitance at A The sending end. B The receiving-end. C The midpoint. D Any convenient point. Answer : B Explanation :
7.
 If L, C and Y are the inductance, capacitance and shunt admittance of a line per unit length, then for length $l$. A The shunt admittance is Y.$l$. B The inductance is L/$l$. C The capacitance is C/$l$. D The shunt admittance/$l$. Answer : A Explanation :
8.
 Transmission efficiency of a transmission line increases with the A Decrease in power factor and voltage. B Increase in power factor and voltage. C Increase in power factor but decrease in voltage. D Increase in voltage but decrease in power factor. Answer : B Explanation :
9.
 Under no-load conditions, the current in a transmission line is because of A Capacitance effect. B Corona effect. C Proximity effect. D Back flow from earth. Answer : A Explanation :
10.
 Which of the following statements are correct  ? A Flow of unduly heavy current is Ferranti effect. B Ferranti effect occurs under unloaded condition of line. C The rise in receiving-end voltage is Ferranti effect. D Bothe (b) and (c) combined is Ferranti effect. Answer : D Explanation :
11.
 In a long transmission line under no-load condition A The receiving-end voltage is less than sending-end voltage. B The sending -end voltage is less than receiving -end voltage. C The sending -end voltage is equal to the receiving -end voltage. D None of these. Answer : B Explanation :
12.
 When is the Ferranti effect on long overhead lines experienced  ? A The line is lightly loaded. B The line is heavily loaded. C The line is fully loaded. D The power factor is unity. Answer : A Explanation :
13.
 Ferranti effect happens in transmission line when the line is A Short and loaded B Long and loaded C Long and unloaded D None of these Answer : C Explanation :
14.
 The  ABCD constants of a  3-phase transposed transmission line with linear and passive elements A Are always equal B Never equal C A  and  D  are equal D B and C are equal Answer : C Explanation :
15.
 The values of A, B, C and D constants for a short transmission line are respectively A Z, 0, and 1 B 0, 1, 1 and Z C 1, Z, 0 and 1 D 1, 1, Z and 0 Answer : C Explanation :
16.
 The angle of A, constant of the transmission line normally lies between A 900 – 700 B 700 – 400 C 400 – 100 D 100 – 00 Answer : D Explanation :
17.
 For a transmission line with resistance  R, reactance X and negligible capacitance, the generalised constant  A  is A 0 B 1 C R + jX D R + X Answer : B Explanation :
18.
 For a medium length transmission line, A is A Equal to B B Equal to C C Equal to D D Not equal to any of the above Answer : C Explanation :
19.
 For transmission line which one of the following relations is true  ? A AD – BC = 1 B - AD – BC = 1 C AD – BC = - 1 D AD – BC = 0 Answer : A Explanation :
20.
 Which one of the following equations is CORRECT  ? A – AB + CD = –1 B AD + CD = 1 C AB – CD = –1 D –AD + BC = – 1 Answer : D Explanation :
21.
 The maximum efficiency in the transmission of bulk ac power will be achieved when the power factor of the load is A Slightly less than unity lagging B Slightly less than unity leading C Unity D Considerably less than unity Answer : B Explanation :
22.
 A transmission line section shows an input impedance of  36 Ω  and  64 Ω respectively, when short circuited and open circuited. What is the characteristic impedance of the transmission line  ? A 100 Ω B 50 Ω C 45 Ω D 48 Ω Answer : D Explanation :
23.
 The open-circuit and short-circuit impedances of a line are  100 Ω  each. What is the characteristic impedance of the line  ? A $100\sqrt{2}\Omega$ B 100  Ω C $\frac{100}{\sqrt{2}}\Omega$ D 50 Ω Answer : B Explanation :
24.
 A cable has inductance of  0.22 mH per  km  and capacitance of  0.202 μF per  km. the surge impedance of the cable is A 28  Ω B 33  Ω C 42  Ω D 50  Ω Answer : B Explanation :
25.
 A  50 Ω  distortion less  transmission line has a capacitance of  10-10 F/m.  What its inductance per metre  ? A 0.25 μH B 500 μH C 5000 μH D 50 μH Answer : A Explanation :
26.
 Which of the following statements is correct  ? A Surge impedance is the impedance at the time of breakdowns of voltage. B Surge impedance and characteristic impedance for a transmission line are the same. C Surge impedance is the impedance of transmission line when corona takes place. D None of the above. Answer : B Explanation :
27.
 The characteristic impedance of a transmission line depends upon A Shape of the conductor. B Conductivity of the conductor material. C Geometrical configuration of the conductors. D None of the above. Answer : C Explanation :
28.
 For a lossy transmission line, the characteristic impedance does  not  depend on A The operating frequency of the line. B The conductivity of the conductors. C Conductivity of the dielectric separating the conductors. D Length of the line. Answer : D Explanation :
29.
 In case the characteristic impedance of a transmission line is equal to the load impedance A The system will resonate badly. B All the energy sent will be absorbed by the load. C All the energy sent will pass to the earth. D All the energy will be lost in transmission line as transmission losses. Answer : B Explanation :
30.
 In a transmission line having negligible resistance, the surge impedance is A $\sqrt{L&space;+&space;C}$ B $\sqrt{\frac{C}{L}}$ C $\sqrt{\frac{1}{LC}}$ D $\sqrt{\frac{L}{C}}$ Answer : D Explanation :
31.
 Characteristic of an overhead line usually in the range of A 100 ohms – 200 ohms B 200 ohms – 300 ohms C 400 ohms – 500 ohms D 0 ohms – 100 ohms Answer : C Explanation :
32.
 The Surge impedance of a  400 kV , 100 km transmission line is 300 ohms. For a  200 km  length the line Surge impedance will be A 300 ohms B 150 ohms C 600 ohms D 400 ohms Answer : A Explanation :
33.
 A transmission line is distortion-less if A RG = LC B RC = GL C R/C  =  G/L D R = G Answer : B Explanation :
34.
 When the load on a transmission line is equal to the surge impedance loading A The receiving-end voltage is less than the sending-end voltage. B The sending -end voltage is less than the receiving -end voltage. C The receiving-end voltage is equal to the sending-end voltage. D None of these. Answer : C Explanation :
35.
 The SIL (Surge impedance loading) of a single circuit  220 kV  line is around A 120 MW B 90 MW C 220 MW D 400 MW Answer : A Explanation :
36.
 What is the Surge impedance loading of a lossless  400 kV , 3-phase, 50 Hz  overhead line of average of Surge impedance of  400 ohms  ? A 400 MW B $400\sqrt{3}&space;MW$ C $\frac{400}{\sqrt{3}}&space;MW$ D 400  kW Answer : A Explanation :
37.
 A lossless radial transmission line with Surge impedance loading A Takes negative  VAR  at sending end and  zero  VAR  at receiving end. B Takes positive  VAR  at sending end and  zero  VAR  at receiving end. C Has flat voltage profile and unity power factor at all points along it. D Has sending end voltage higher than receiving end voltage and unity power factor at sending end Answer : C Explanation :
38.
 What does the standing wave ratio  (SWR)  of unity imply  ? A Transmission line is open-circuited. B Transmission line is short-circuited. C Transmission line’s characteristic impedance is equal to load impedance. D Transmission line’s characteristic impedance is not equal to load impedance. Answer : C Explanation :
39.
 Full-load compensation in a line requires A Shunt capacitors B Series capacitors C Transformers D Shunt reactors Answer : A Explanation :
40.
 Use of additional shunt capacitor can be made for increasing the capability of line as it A Reduces surge impedance  Z0 B Increases phase shift  $\beta$ C Increase in $\alpha$ D All of the above Answer : A Explanation :
41.
 The conductor of the overhead lines are A Solid B Stranded C Both solid and stranded D None of the above Answer : B Explanation :
42.
 High voltage transmission lines use A Suspension insulators B Pin insulators C Both (a) and (b) D None of the above Answer : A Explanation :
43.
 Multicore cables generally use A Square conductors B Circular conductors C Rectangular conductors D Sector-shaped conductors Answer : D Explanation :
44.
 Distribution lines in India generally use A Wooden poles B R.C.C poles C Steel towers D None of the above Answer : B Explanation :
45.
 The materials commonly used for insulation in high voltage cables is A Lead B Paper C Rubber D None of the above Answer : B Explanation :
46.
 The loads on distributors systems are generally A Balanced B Unbalanced C Either of the above D None of the above Answer : B Explanation :
47.
 The power factor of industrial loads is generally A Unity B Lagging C Leading D Zero Answer : B Explanation :
48.
 Overhead lines generally use A Copper conductors B All aluminium conductors C A.C.S.R conductors D None of these Answer : C Explanation :
49.
 In transmission lines the cross-arms made of A Copper B Wood C R.C.C D Steel Answer : D Explanation :
50.
 The material generally used for armour of high voltage cables is A Aluminium B Steel C Brass D Copper Answer : B Explanation :