Re: HV xray cable revisited

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>

The best place to find this stuff is on a large
industrial or municipal construction project. We
probably threw away literally tons of that stuff. It
went to a salvage yard for the price of scrap copper.
Ours was 15 kV rated (12,470 kV distribution). You may
also find it at a salvage yard, before they chop it
into bite sized chunks.

Adam

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: Terry Fritz
> <vardin@xxxxxxxxxxxxxxxxxxxxxxx>
>
> Hi,
>
> What would be ideal... Is to get your hands on this
> type of stuff...
>
>
http://www.okonite.com/Product_Catalog/section2/sheet14.html
>
> Underground, 60Hz rated 15kVac... It is all 150
> amps or greater :o))) :-)))))  DigiKey don't sell
> it, but I bet they "throw away" those 200 foot
> extra lengths...  Maybe E-bay...
>
> Note all the "semiconducting layer
> stuff"...  Don't go messing with that!!!  Just
> use the cables just like they were designed to be
> used...
>
> "105°C continuous operating temperature. 140°C
> emergency rating. 250°C short circuit rating.
> Excellent corona resistance. "
>
> This stuff is real "high tech" so don't go
> changing the "system"!!!  You can probably dig the
> sit to find the details.
>
> http://www.okonite.com/overview.html
>
> But all the corona, HV, leakage, shielding stuff
> has been pretty well figured out over that last
> 100 years, so you should not go changing it on a
> "10 second whim"!!!...  The HV cables are darn
> good just as they are and used just as they are
> meant to be used...  Avoid the oil and paper
> solutions from the past :o)))
>
> Cheers,
>
>          Terry
>
>
>
>
> At 09:51 PM 1/6/2006, you wrote:
> >Bart,
> >
> >That's the way that I do it ;^) The capacitance
> makes the
> >exterior of the cable "charged" and it can give a
> little "shock"
> >if handled energized without the braid being
> grounded. :^O This
> >is exactly the way that I feed the power to the
> base of my
> >15 kVA "Green Monster" coil system, which can be
> seen
> >@: http://dawntreader.net/hvgroup/david/gm.html
> >The x-ray cables can be clearly seen leading up to
> the base
> >of the primary circuit in photo # 22 (I believe),
> the only spark
> >shot taken in daylight conditions. I ground the
> braiding to the
> >mains ground back at the pole pig's outer tank
> ground. Works
> >great with no failures of the insulation running up
> to around 17
> >kVAC from the pig when overdriven by a 280 volt
> input from
> >the control panel variac.
> >
> >David Rieben
> >
> >
> >
> >----- Original Message ----- From: "Tesla list"
> <tesla@xxxxxxxxxx>
> >To: <tesla@xxxxxxxxxx>
> >Sent: Friday, January 06, 2006 9:17 PM
> >Subject: Re: HV xray cable revisited
> >
> >
> >>Original poster: "Barton B. Anderson"
> <bartb@xxxxxxxxxxxxxxxx>
> >>Hi,
> >>If this is the case, then all those coilers
> >>running xray cable should be grounding the
> >>braid? It seems the proper method to use this
> >>cable would be to sweat back (or strip back)
> >>the braid (~ 10") on each end and then ground the
> braid?
> >>Take care,
> >>Bart
> >>Tesla list wrote:
> >>
> >>>Original poster: Terry Fritz
> <vardin@xxxxxxxxxxxxxxxxxxxxxxx>
> >>>
> >>>Hi,
> >>>
> >>>The black coating is "resistive" not
> >>>"conductive".  If you ground one end and run
> >>>say 60Hz AC across it, the far ungrounded end
> >>>can and probably does get to a pretty high
> voltage.
> >>>
> >>>For example, if the cable is ten feet long
> >>>with a resistance of say 10k ohms / foot, then
> >>>the far end of the cable is 100k ohms to
> >>>ground.  Now if we "assume" a capacitance of
> >>>10nF in the cable at 60 Hz we have 265k ohms
> >>>or leakage reactance to the outer layer.  If
> >>>you put 15kV into the cable, the outer layer
> >>>voltage is 100k / (265k + 100k) x 15k = 4110
> >>>volts.  So it arcs to ground very well...
> >>>
> >>>The conductive outer braid was meant to
> >>>prevent that by providing a solid low
> >>>resistance conductive path to ground which
> >>>reduces the outer voltage to very near zero.
> >>>
> >>>Cheers,
> >>>
> >>>         Terry
> >
>
>
>