Question

The surge impedance of a 400 km long overhead transmission line is 400 ohms. For a 200 km length of the same line, the surge impedance will be _________.
1. 200 ohms
2. 800 ohms
3. 400 ohms
4. 100 ohms

Answer 1

Correct Answer - Option 3 : 400 ohms

The surge impedance is always same in any length of the transmission line. It does not depend on the length of the transmission line

\({Z_s} = \sqrt {\left( {\frac{L}{C}} \right)}\)

Here

L = transmission line inductance,

C = transmission line capacitance,

Zs = surge impedance

For a 200 km length of the same line, the surge impedance

= 400 ohms