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Electrical Engineering Objective Questions { Power System }

239. Surge impedance of 50 miles long underground cable is 50 ohms. For a 25 miles length it will be
A. 25 ohms
B. 50 ohms
C. 100 ohms
D. none of these
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240. Capacitance and inductance per unit length of a line operating at 110 kV are 0.01 mF and 2 mH. The surge impedance loading of the line will be
A. 40 MVA
B. 30 MVA
C. 27 MVA
D. none of these
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241. Sending end voltage of a feeder with reactance 0.2 p.u. is 1.2 p.u. If the reactive power supplied at the receiving end of the feeder is 0.3 p.u., the approximate drop of volts in the feeder will be
A. 0.2 p.u.
B. 0.06 p.u.
C. 0.5 p.u.
D. 0.072 p.u.
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242. Presence of earth in case of overhead lines
A. increases the capacitance.
B. increases the inductance.
C. decreases the capacitance.
D. decrease the inductance.
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243. Effect of increase in temperature in overhead transmission lines is to
A. increase the stress and length
B. decrease the stress and length.
C. decrease the stress but increase the length.
D. none of these
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244. Ferranti effect on long overhead lines is experienced when it is
A. lightly loaded.
B. on full load at unity p.f.
C. on full load at 0.8 pl. lag.
D. in all these cases.
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245. In-rush current of a transformer at no load is maximum if the supply voltage is switched on
A. at zero voltage value.
B. at peak voltage value.
C. at V/2 value.
D. at .1i /2 V value
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