When alternating current flows through parallel cables, their magnetic fields interact and push the current density away from the adjacent sides. This crowding of current reduces the effective cross-sectional area of the wire, significantly increasing its AC resistance. The effect worsens at higher frequencies and in closely bundled transmission lines, causing excess heating and power loss.
We've to derate these bundled cables because the proximity effect is pushing their operating temperature too high at full load.
Do not mix it up with
- Skin effect: Skin effect pushes current to the surface of a single conductor due to its own magnetic field, while proximity effect pushes current to one side due to the magnetic field of a neighboring conductor.
Related terms
Skin effect
Tendency of alternating current to crowd toward the surface of a conductor as frequency rises.
Harmonics
Voltage or current components at whole multiples of the supply frequency, produced mostly by nonlinear loads.
Conductor
A physical material or wire designed to carry electric current with minimal resistance.