[sdiy] OT: 7200 volt truck-to-ash covertor circuit.

[J. Larry Hendry]

> ----- Original Message -----
> From: Jason <zzyzx1710 at earthlink.net>
> Good, then you should be able to shed some light on why there isn't any
insulation on high voltage lines...

Jason,

It would not work.  We do put insulation on underground cable - duh.  :)
But, overhead wire contracts and expands as it is loaded and unloaded.  The
actual loadability of transmission lines is determined by the sag between
poles at a certain operating temperature (i.e. code clearance to whatever is
under it).  Normally, lines are limited to 80C conductor temperature.
However, in some cases, that can go as high as 160C if the wire is properly
constructed (aluminum over steel core).

The heating and cooling cycle and expanding and contracting would soon
destroy the dielectric of any insulation.

Having said that, some overhead wire has "insulation."  It is called
Hendricks cable (up to 15KV class).  But, it is not considered "insulation".
You cannot touch it.  However, it is used in areas of heavy trees so that
some tree contact is tolerated.  Normally, tree contact causes burning.

Secondary voltage wires (600 volts and below) are almost always insulated
(because you can).

Plus, once you get into higher voltages, insulation would become much
heavier than the wire itself.

Larry Hendry