POWER SYSTEMS 2

POWER  SYSTEMS

21. The corona loss on a particular system at 50HZ is 1kw/km/ph. The corona loss at 60 HZ is
a) 1kw/ph/km
b) 0-83 kw/km/ph
c) 1.2 kw/km/ph
d) 1.13 kw/km/ph
ans: d

22. A loss-less radial transmission line with surge impedance loading
a) takes negative VAR at sending end and zero VAR at receiving end
b) take positive VAR at sending end and zero VAR at receiving end
c) has flat voltage profile and unity power factor at all points along with it
d) has sending end voltage higher than receiving end voltage and unity power factor at sending end
ans: c

23. Consider along, two wirelines composed of solid round conductors. The radius of both conductors is 0.25 cm and the distance between their centers is 1m. If this distance is doubled, then the inductance per unit length
a) doubles
b) halves
c) increase but does not double
d) decreases but not halve
ans: c

24. A long wire composed of a smooth round conductor runs above and parallel to the ground. A high voltage exists between the conductor and the ground. The max electric stress occurs at.
a) the upper surface of the conductor
b) the lower surface of the conductor
c) the ground surface
d) none of the above
ans: b

25. Bundled conductors are mainly used in high voltage OH transmission lines to
a) reduce transmission line losses
b) increase the mechanical strength of the line
c) reduce corona
d) reduce sag
ans: c