Electrical Power Systems

454 Electrical Power Systems
93. Charging current due to capacitance C when a single phase line is transmitting power at
a voltage v and frequency w is
(a) – v/jwc (b) jwv/c (c) v/c (d) jwcv
94. The presence of earth alters the
(a) electric field of the line (b) capacitance of the line
(c) both (a) and (b) (d) inductance of the line.
95. The rise of temperature in transmission line
(a) increase the stress and the length
(b) decrease the stress and increase the length
(c) decrease the stress and the length
(d) increase the stress and decrease the length.
96. The skin effect in conductors is due to non–uniform distribution of current in it and major
portion of the current is near the ... of the conductor.
(a) surface (b) centre (c) axis (d) radial lines.
97. The effective resistance of conductor is increased by
(a) skin effect (b) proximity effect (c) corona effect (d) both (a) and (b).
98. In both skin effect and proximity effect
(a) the effective internal reactance of the conductor gets decreased
(b) their effect depends upon conductor size d, frequency f, resistivity r and permeability µ r.
(c) the effect is negligible at power frequency and small conductors, but the effect is large
for higher frequency and big conductors
(d) all of these.
99. A two terminal pair of network of a transmission line can be represented by a
(a) p–network (b) T–network (c) either (a) or (b) (d) tree network.
100. or a short transmission line
(a) VR = VS – ISZ (b) A = D = 1 (c) C = 0 and B = Z (d) all of these.
101. A medium transmission line has length over 80 Km and upto 250 Km has negligible
(a) resistance (b) inductance (c) conductance (d) capacitance.
102. The characteristic impedance of a loss–less overhead line has a value of
(a) 400 to 600 ohms (b) 40 to 60 ohms (c) 100 to 200 ohms (d) 30 to 300 ohms.
103. The characteristic impedance of a loss–less cable is
(a) 400 to 600 ohms (b) 40 to 60 ohms (c) 100 to 200 ohms (d) 30 to 300 ohms.
104. erranti effect states that the receiving end voltage on no load is
(a) equal to that at the sending end (b) less than that at the sending end
(c) more than that at the sending end (d) either (b) or (c).
105. At no load, the loss in a long transmission line is
(a) 0 (b) 1
0
2
2
RI (c) 1
0
3
2
RI (d) 1
0
4
2
RI
106. Advantages of constant voltage transmission are:
(a) improved power factor at heavy loads
(b) same voltage is maintained at all loads
(c) increased power transmission over long distance
(d) all of the above.
107. Commonly used equivalent network of a transmission line is
(a) p (b) T (c) ladder network (d) either (a) or (b).