Re: HV xray cable revisited

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>

Oops! Make that 12.47 kV.

Adam

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

> 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
>  > >
>  >
>  >
>  >