Line Capacitance and Earth Capacitance Effect in Transmission Line

There are some unwanted capacitance effect that occurs in the transmission line. Line Capacitance and Earth Capacitance Effect are the most important effects. Generally, in short-distance and low-voltage transmission lines, they do not occur but in the large-distance and high-voltage transmission lines, those capacitance effects occur. Those unwanted capacitance effects have some advantages as well as some disadvantages.

What is Line Capacitance?

The capacitance between two phases or lines is called Line Capacitance or line-to-line capacitance.

In the transmission line, two adjacent phases or conductors are separated by the air, so when the potential difference occurs between those conductors, a capacitance effect is created. This is called Line capacitance. Here the Air is used as a dielectric material and the two adjacent conductors act as plates. This effect is also called stray capacitance.

What is Earth Capacitance?

As the neutral is grounded in substations, so the earth can be considered as a conductor which have zero potential. So there is a potential difference between phase or line and earth. For this reason, a capacitance effect is occurs taking the air as a dielectric material which is called Earth capacitance or Line to Earth Capacitance.

Line to Neutral Capacitance?

The capacitance between phase and neutral is called a phase or line-to-neutral capacitance. Generally, in the transmission line, the neutral wire is not used. The neutral wire is used for mainly distribution purposes.

Advantages of Capacitance Effect in Transmission Line

There is only one advantage of the capacitance effect in a transmission line which is power factor improvement. The capacitance effect compensates a part of inductive reactive power and improves the power factor. As the power factor improves, the copper loss decreases, and efficiency increases.

Disadvantages of Capacitance Effect in Transmission Line

There are many disadvantages of the capacitance effect in the transmission line which are explained below.

1. The capacitance effect takes the charging current from the transmission line which is a waste of energy.

2. It will increase the receiving end voltage more than the sending end voltage at light load or no load condition. As the transformers and other devices are designed at rated voltage, so they may be damaged if the voltage is increased. Generally, shunt reactors are used in substations during light load or no load conditions to maintain the receiving end voltage.

3. The Ferranti Effect also occurs due to the capacitance effect in the transmission line.

Read Also:

• Main Difference Between Earthing and Grounding
• Why capacitor is connected in parallel not in series for Power Factor improvement?
• [Actual] Purpose and Function of Earth Wire
• Why Overhead Transmission Line Conductors are not insulated?
• What is Common Grounding? Examples, Advantages

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