John Fields wrote:

I would think that simple thermal effects would cause charge to flow
closer to the surface just because that part of the conductor would
be cooler, ergo lower resistance than the hotter interior.


To which Tzortzakakis Dimitrios replied:

That can happen in high impulse short circuit currents.An unfused
220 V
circuit shortcircuited between live and earth, can have an impulse
current
of 20 kA.Properly fused with a circuit breaker, up to 50 A.In normal
operating conditions, a transmission line of 150 kV operating at 200
A with
an ambient teperature of 20 deg.C (65deg.F)should not exceed 50
deg.C(105deg.F)however as it operates continually at these
conditions the
temperature is uniform across the conductor (ACSR).

---
I think you misunderstood my point, which was that the copper at the
surface of the conductor would, by virtue of radiation and
convection, be cooler than the copper at the center of the
conductor. Such being the case, the resistance of the cooler copper
at the surface would be less than the resistance of the copper in
the core, leading to a non-uniform radial current gradient in the
conductor.

--
John Fields
Professional Circuit Designer