A long overhead transmission line is terminated by its characteristic impedance. Under this operating condition, the ratio of the voltage to the current at different points along the line will

A long overhead transmission line is terminated by its characteristic impedance. Under this operating condition, the ratio of the voltage to the current at different points along the line will

Right Answer is:

Remain the same at all points

SOLUTION

A long overhead transmission line is terminated by its characteristic impedance. Under this operating condition, the ratio of the voltage to the current at different points along the line will remain the same at all points.

The two important electrical properties of  symmetrical network are:

  1. Characteristic impedance (Zo)
  2. Propagation constant.

Characteristic Impedance (Zo)

  1. Characteristic impedance is a fine and useful concept of the transmission line.
  2. When no part of the power sent down an infinite line returns no reflection, there is no loss of power.
  3. When a line that is terminated at its characteristic impedance, behaves as an infinite line, it will also have no reflection.
  4. A long overhead lossless power transmission line is terminated with its characteristic impedance. It indicates that the reflection coefficient is zero.
  5. When a line is terminated in its characteristic impedance, it is said to be correctly terminated or termed as a non-resonant line.
  6. The characteristic impedance of a uniform transmission line is defined as the steady-state vector ratio of the voltage to the current at the input of an infinite line.

Electrical energy on a length of a line equals CV2/2

Where

C = Capacitance
V = magnitude of the traveling voltage wave

The magnetic energy of the length of the line is equal to LI2/2

Where

L = Inductance of the line
I = Magnitude of the traveling current wave

$\frac{{C{V^2}}}{2} = \frac{{L{I^2}}}{2}$

Hence

$\frac{V}{I} = \sqrt {\frac{L}{C}}$

Hence in the surge impedance loading, the ratio of traveling voltage to the traveling current is determined by the ratio of L and C and in surge impedance, the voltage and current are in the same phase at any point along the line.

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