On 29/07/2014 16:15, The Natural Philosopher wrote:
On 29/07/14 11:14, John Williamson wrote:
On 29/07/2014 07:43, harryagain wrote:
"John Williamson" wrote in message
...
On 28/07/2014 19:20, harryagain wrote:
"The Natural Philosopher" wrote in message
...
On 28/07/14 08:22, John Williamson wrote:
On 28/07/2014 02:03, The Natural Philosopher wrote:
On 27/07/14 22:45, tony sayer wrote:
In article
,
scribeth thus
Nightjar wrote:
AC for simple long-distance transmission...
Except for underwater cables, where it can cause unacceptable
transmission losses.

How does immersing a 11kV AC cable in water increase transmission
losses? This isn't a joke question, I can't see how the medium
surrounding a cable changes the action of the cable itself, other
than cooling effects.

jgh

Inductive and Capactive losses theres some stuff on the AAB
website
somewhere;!...

Not sure that induction plays any part..

Transmission lines have a calculable inductance per metre, and as
the
length approaches infinity, so does that inductance.

There is a characteristic impedance for transmission lines, which
affects both transmission and losses.


So, having taught grandmother to suck eggs, where is the power loss
due
to
inductance?

The loss arises from energy taken to reverse the magnetic field.
https://en.wikipedia.org/wiki/Magnetic_hysteresis


Not in copper or aluminium wires.

Any magnetic field takes energy to establish or reverse it.
Magnetic fields are associated with any electric current.


That's not what it says in the article you referred us to.

And in fact establishing a magnetic filed takes energy, but reversing it
you get the energy back.

That's how transformers work.


You get *all* the energy back, less the hysteresis losses in the iron
core. There are no such losses in the copper windings, and air cored
transformers don't suffer them either, they're just not very practical
at 50Hz or so due to the size they'd have to be.

To get back to the original consideration of copper or aluminium
transmission lines, there are no hysteresis losses in the line. You will
get some if the lines are made of ferrous metals, though, but the
hysteresis losses would be swamped by the resistive ones.

--
Tciao for Now!

John.