Objective Questions "#!
82. Inductance of a conductor due to its internal flux is
e
j
2 p ´ 10 -7 H/m 7 83. Inductance between two conductors of diameter D1 and D2 is -7 (a) 2 p ´ 10 H/m
(a)
-7 (b) 2 p ´ 10
FG IJ H K F D IJ H/m ´ ln G HD K
D2 1 ´ 10 -7 ´ H/m 2 D1
-7 (c) 10
-1
H/m
2
FG D IJ H/m HD K F D IJ H/m. lnG HD K
-7 (b) 2 ´ 10 ln
-7 (d) 2 p ´ 10
1
-7 (d) 0.5 ´ 10 H/m.
(c)
2
1
2
1
84. A conductor has seven identical strands of r = 1 cm each. The GMR of the conductor is (a) 7 cm (b) 3.5 cm (c) 2.177 cm (d) 0.177 cm 85. An ACSR conductor has (n 1) layers around its single centre strand, the total number of strands will be (b) 3n2 3n 1 (c) 3n2 + 3n 1 (d) 3n2 3n + 1. (a) 3n2 + 3n + 1 86. An ACSR conductor has seven steel strands, it is surrounded by twenty four aluminium conductors, it is specified as (a) 31 ACSR (b) 31/7 ACSR (c) 7/31 ACSR (d) 24/7 ACSR. 87. The value of inductance per conductor in three phase line is ... times the loop inductance for single phase lines
1 1 (b) (c) 1 (d) 2 3 2 When the conductors of a three phase circuit are not spaced equilaterally, the transposition is done to (a) decrease the line inductance per phase (b) minimize the effect of adjoining communication circuit (c) balance the three phases of the circuit (d) both (a) and (b). In EHV lines, the high voltage gradient at the conductors is reduced by (a) transposing the lines (b) increasing the height of the supporting towers (c) two or more conductors per phase in close proximity and increasing the spacing between the phases (d) all of these. The transmission line inductance contributed by (a) the current in the conductor (b) the current in other conductors (c) extra high voltage in between the conductors (d) all of these. Regulating transformers are used in power system to control (a) power factor (b) load flow (c) voltage (d) none of these. The ratio of capacitance of line to neutral and line to line capacitance of a transmission line having two conductors is (a)
88.
89.
90.
91. 92.
(a)
1 4
(b)
1 2
(c) 1.0
(d) 2.0