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What are the Line Constants in a Medium Transmission Line Mcq?

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Is the constant of the transmission line; Resistance, inductance and capacitance. All lines of the medium transmission line are considered constant. That is, along with the resistance and inductance of the line, the capacitance is also considered.

Although the capacitance extends evenly along all the lengths of the line, the response of the capacitance is considered to be split at the customer and transmitter ends or concentrated in the medium of the line for the convenience of calculation.

Since the length of the short-haul transmission line is shorter and the operating voltage is shorter, the capacitance response can be ignored. But since the length of the medium transmission line is longer (50 to 150 km) and the operating voltage is above 20 KV, the capacitance response cannot be ignored. That is why the response of the capacitors must be taken into account in order to make the calculation of the line more acceptable and to get the correct result.

Capacitance is equally present throughout the line. But to make the calculation easier, the capacitance of the whole line is assumed to be stored in the shape of a shunt capacitor in one or two places. The results obtained by calculating the capacitance of the whole line in this way are fairly accurate.

Three methods are used to determine the values of the medium transmission line constants,

For example;

1. End condenser method,

2. Nominal ‘T’ method,

3. Nominal “π” method

Let’s discuss the medium transmission line constants in detail.

Also Read: Advantages and Disadvantages of AC & DC Transmission

Effect of line resistance on the medium transmission line

Resistance depends on which metal the conductor is made of. We know that the formula for resistance is  R=frac{rho L}{A} . Resistance-induced effect refers to skin effect, eddy current, hysteresis, die-electric loss-induced obstruction.

Effect of line inductance on the medium transmission line

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When AC current flows through a conductor, the self-inductance of the conductor is created by the contact of the variable flux conductor.

Self-inductance is the property or characteristic of an electrical circuit, which determines the rate of change of current given in the circuit. Its symbol is L.

We get the formula for the reactance, R = 2pi fL   and the line drop IX_L , (reactive drop of the line), where, I = the current of the line (in amperes).

Effect of line capacitance on the medium transmission line

We know that when two conductors are separated by a non-conductive material, capacitors are formed. Similarly when the two conductors of an overhead transmission line are separated by air it acts as a capacitor. Capacitance, C = frac{q}{v} farad


C = Charge

V = Potential difference

Below are the figures for the uniformly distributed capacitance of the transmission line and the concentrated capacitance of the line:

Effect of line capacitance on the medium transmission line

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