TRANSMISSION AND DISTRIBUTION OF ELECTRICAL POWER

1.Corona losses are minimized when
a) conductor size is reduced
b) smooth conductor is used
c) sharp points are provided in the line hardware
d) current density in the conductors is reduced.
ans. b

2. Consider a long ,two-wire line composed  of solid round conductors. The radius of both conductors is 0.25 cm and the distance between their centres is 1m. If this distance is doubled, then the inductance per unit length
a) doubles
b) halves
c) increases but does not double
d) decreases but does not halve
ans. c

3. A 3-phase transmission line has its conductors at the corners of an equilateral triangle with side 3m . The diameter of each conductor is 1.63 cm. The inductance of the line per phase per km is
a) 1.232 mH
b) 1.182 mH
c) 1.093 mH
d) 1.043 mH
ans. c

4. For single-phase over head line having solid copper conductors of diameter 1 cm spaced 60 cm between centers , the inductance in mH/km is
a) 0.05 + 0.2 log 60
b) 0.2 log 60
c) 0.05 + 0.2 log 60/0.5
d) 0.2 log 60/0.5
ans. c

5. The conductors of a 10 km long , single phase, two wire line are seperated by a distance of 1.5 m.The diameter of each conductor is 1 cm . If the conductors are of coppers, the inductance of the circuit is
a) 50.0 mH
b) 45.3 mH
c) 23.8 mH
d) 19.6 mH
ans. c

6. The inductance of a power transmission line increases with
a) decrease in line length
b) increase in diameter of conductor
c) increase in spacing between the phase conductors
d) increase in load current carried by the conductors
ans. c

7. Bundled conductors are employed to improve
a) appearence of the transmission line
b) mechanical stability of the line
c) current carrying capacity of the line
d) corona performance of the line
ans. d

8. Bundled conductors are mainly used in high voltage overhead transmission lines to
a) reduce transmission line losses
b) increase mechanical strength of he line
c) reduce corona
d) reduce sag
ans. c

9. A 3-phase overhead transmission line has its conductors horizontally spaced with spacing between adjacent conductors equal to'd'. If now the conductors of the line are rearranged to form an equilateral traingle of sides equal to 'd' then
a) average capacitance and inductance will increase
b) average capacitance will decrease and inductance will increase
c) average capacitance will increase and inductance will decrease
d) surge impedance loading of the line increases
ans. c

10.For equilateral spacing of conductors of an untransposed 3-phase line, we have
a) balanced receiving-end voltage and no communication interference
b) unbalancing receiving-end voltage and no communication interference
c) balanced receiving-end voltage and communication interference
d) unbalanced receiving-end voltage and communication interference
ans. d