For some time, I've been trying to create some mental image with which to
visualize the induction into ground which takes place within the induction
field around an elevated radial. I've also been trying to form a mental
image of the current which results. I doubt that the present visualization
is very accurate. If anyone has facts or even educated guesses, I'd be
very interested in hearing about them and suspect others would too.
Here's where I am at this point:
Current is flowing in an elevated radial. That current causes an induction
field to exist around the radial. The induction field induces a voltage
(note: NOT a current). The induced voltage causes a current to flow in the
lossy ground. (that's why the note in the previous sentence: it is often
said that a current is induced, but it isn't: a voltage is induced and if
there is a path for current to flow, the voltage causes it to flow). So
far, so good. Now the picture, at least for me, gets very murky. If a
voltage is flowing in a linear conductor (wire, pipe, tower, etc.), it's
easy to visualize the current flowing back and forth along the conductor.
But in the ground, we now have a solid three-dimensional conductor, rather
than a linear one. So now, we can't think of the current as flowing back
and forth along a line, because presumably the current will spread out as
it flows. Furthermore, it isn't flowing between two points with a certain
known, predictable voltage between them. In two dimensions, I would
visualize the current as spreading out into a series of ellipses, similar
to the pattern made by iron filings in the presence of a magnet. What
about the third dimension? Well, there ain't no ground above ground. So
not much current is gonna flow in the air. Also, as we penetrate into the
soil I find it very difficult to imagine much current flowing very far
below the surface. My only basis for this statement is pure intuition.
And I have no idea whatsoever what the geometry of the current might be.
I suspect W8JI said it exactly right: the ground current cannot be predicted.
Comments anyone?
73
Larry, N9DX
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