Why do transmission lines have capacitance?

Capacitance in a transmission line results due to the potential difference between the conductors. The conductors get charged in the same way as the parallel plates of a capacitor. Capacitance between two parallel conductors depends on the size and the spacing between the conductors.

Are transmission lines inductive or capacitive?

A transmission line is a pair of parallel conductors exhibiting certain characteristics due to distributed capacitance and inductance along its length. When a voltage is suddenly applied to one end of a transmission line, both a voltage “wave” and a current “wave” propagate along the line at nearly light speed.

What happens if the capacitance of a transmission line is very high?

ADVERTISEMENTS: If the capacitance of an overhead line is high, the line draws more charging current, which compensates or cancels the lagging component (reactive component) of load current (under normal load conditions the load is inductive one). Hence the resultant current flowing in the line is reduced.

Why is capacitance effect more predominant in a short cable than a short overhead line of same length?

The capacitance of a cable transmission line is very larger than that of an overhead line of the same length due to the following reasons. The distance between the conductor is very small. The distance between the core and earth sheath of the overhead line is very small.

How does capacitance affect transmission lines?

The capacitance of a line gives rise to the leading current between the conductors. The capacitance of the line is proportional to the length of the transmission line. Their effect is negligible on the performance of short (having a length less than 80 km) and low voltage transmission line.

What is a lossless transmission line?

The analysis of lossless lines provides an accurate approximation for real transmission lines that simplifies the mathematics considered in modeling transmission lines. A lossless line is defined as a transmission line that has no line resistance and no dielectric loss.

Why there is no capacitance in short transmission line?

A transmission line having its length less than 80 km is considered as a short transmission line. In short transmission line capacitance is neglected because of small leakage current and other parameters (resistance and inductance) are lumped in the transmission line.

What is the relation between length of the cable and the capacitance?

The capacitance is directly proportional to the length of the cable.

How capacitance of a transmission line are affected by the spacing between the conductors?

Capacitance of a two wire transmission line is Where, d = Space between the conductors r = radius of the conductors Therefore, if we increase the spacing between the phase conductors, the line capacitance will decrease. Therefore, capacitance is higher.