Question

Overhead transmission lines are transposed to ___________ the ______________ of the phases.

a)increase, capacitance

b) reduce, resistance

c) reduce, inductance

d) balance, inductance

The outside diameter of a stranded conductor is 1 inch. The cross sectional area of the conductor is,

a) 1000 kcmil

b)12000 kcmil  

c)cannot be determined

d) 1000 cmils

Inductive reactance at 1 ft spacing, Xa depends on __________ but is independent of ___________.

a) conductor spacing, conductor type

b) frequency, conductor type

c) conductor type, conductor spacing

d) conductor spacing, frequency

Answer 1

**option D correct !!

Because in unsymmetrical transmission line we have unequal inductances per phase causing unequal voltage drops and so we do transposition. So ,we need to equalize or balance inductances in each phase to equalize voltage drops , so we do transposition!!

**Option A

1 inch = 1000 circular mils = diameter (d)

Area = diameter ²

(formula applicable only when diameter given in circular mils)

So area = 1000² = 1000000 cmil = 1000 kcmil (since 1k =1000)

**Option B

Xa= 2.022 * 10^-3 * f * ln (1/Ds)

Where

f= frequency

Ds = GMR or geometric mean radius

So , clearly Xa depends on frequency and independent of conductor type (as no conductor specific factor is present in formula )

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