ELECTRICAL SKIN EFFECT
“Electrical skin effect is the phenomena that arises due to unequal distribution of alternating current over the cross sectional area of metallic conductor.”
In other words, it is the condition in power lines when the concentration of charge electrons over the surface of conductor increases as compared to internal area of the conductor. Due to skin effect the current within the conductor usually flows over the conductor surface. Skin effect occurs only in long transmission wires. It is neglected in short power lines. In DC current lines, skin effect is zero as their is no frequency change in dc lines.
How skin effect arises in electrical power system?
Before going deep into the topic of skin effect, we should know the basic cause of skin effect in conductor wires. The fundamental reason for the cause of skin effect is inductance effect within the conductor. As we know that, transmission lines conductor are twisted together forming and inductor behavior within it. Inductor opposes the change of state of current passing through it according to lenz’s law. In our electrical power systems, transmission lines carry huge value of alternating current at higher frequencies. Due to higher frequencies, impedance also increases given by the relation XL= 2*3.14*f*L.
Imagine, a conductor is split into numerous strands and small part of current flows through each strand. Each strand will have its own value of inductance according to its position. The inner strands will have greater magnetic flux as compared to other strands. This results in higher inductance within the inner core region of conductor. It is the property of current to flow over from less reactive path thus leading current to flow on the surface of the conductor that is less resistive to current as compared to inner region. This is how skin effect arises.
Factors effecting skin effect
Skin effect depends upon the following factors
Better the permeability of the material, higher will be the value of skin effect.
Skin effects increases with the increase in frequency.
Cross Sectional Area:
Increase in cross sectional area of conductor increases skin effect.
The shape of conductor also effects skin effect. In solid conductor skin effect is more as compared to stranded conductor as solid conductor has more surface area.
Also read the following related topics:
|What is electrical proximity effect in power system?|
|What is electrical corona effect in power system?|