Skin Effect in Transmission Lines

In an earlier article, we have studied the corona effect in the power system. Here, I will explain the skin effect with basic terms like definition, diagram, affecting factors, formula, etc.

Let’s dive from the basic.

What is skin effect in electrical?

The accumulation of current on the surface of the conductor and the tendency of the flow of the current on the surface of the conductor is referred to as a ‘Skin-effect‘.

This effect is mainly due to the magnetic flux linkage of the center conductor is more compared to the outermost conductor.

Due to that the impedance or inductance of the central strand of the conductor is more which results in the deviation of the current through the outer strand of the conductor.

So, the non-uniformity of these uneven flux linkages would be the cause of this effect.

Geometry of Conductor

How to calculate Skin Effect?

Here, in the above diagram dark portion indicates the current density which is more at the outer surface of the conductor. And it goes decreasing when we move towards the core of the conductor.

Due to this imbalance of the magnetic flux linkage then the effective area of the current-carrying path decreases and which creates the difference between the AC and DC resistance.

As in DC system this effect is not present. This AC resistance can be approximated by-

equation of skin effect

Skin effect basically depends on skin depth.

What is a skin depth?

The definition of skin depth is the distance from the outer surface to the strand of the conductor where the flow of current is maximum. This is indicated as ‘ δ ’ in the above figure.

Skin depth (δ) is calculated by using the formula as below,


f- Frequency of the system

μ- Relative permeability of conductor

σ- Conductivity of conductor

Skin depth is low which indicates the skin effect is more or vice versa.

This effect is more in communication lines compared to the power line as the frequency of the communication line is in MHz.

This effect is low for the hollow conductors, so they are preferred for the large current rating of the load.

This is the explanation of the skin effect in power transmission lines. In an upcoming tutorial, I will explain the proximity effect.

Online MCQ Quiz

I’m asking you 10 simple MCQ question on whatever we have learnt. Let’s test your knowledge with our Skin-Effect MCQ Quiz‘.

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