Skin Effect In Transmission Lines

Skin Effect

        For a direct current flowing in a conductor,the current is uniformly distributed across the section of conductor where as alternating current is non-uniform with outer filament of conductor carry more current than filament closer to centre. Hence higher resistance to alternating current than the dc current
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        So the non-uniform distribution of ac current over the cross section of conductor causing current density at surface of conductor to be higher than current density at its centre. This phenomenon is called Skin Effect. This effect is more pronounce as supply frequency increases,also it depends on size and shape of conductor,with conductor size increases Skin Effect increases.

        Consider a solid round conductor having number of annular filament of equal cross section area. The flux linkages per ampere to the inner filament will be more as compare to the outer filament,hence inductance or inductive reactance is greater for the inner filament. This results in more current in the outer filament that are closer to conductor surface. This non-uniformity of flux linkage is main cause of Skin Effect. In this effective resistance of conductor will increase. This Effect occurs in overhead line.