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Re: HV xray cable revisited

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Excellent Mike!
I don't think anyone ever envisioned actually stripping off the insulation. The whole point in the beginning of this thread was just to get rid of the arcing quickly for a particular run. By getting the wire away from anything it might arc to or insulating away from those things was the obvious quick solution.
I personally don't have the problem nor use xray cable after my early on experience (which this thread has shed some light on why I possibly experienced the arcing). I've since done away with such problems, but if coilers do use this cable type, Carl seems right on track with where this thread was going.
Terry also showed some nice cable by Okonite, a website we've probably all run across at one time or another when researching hv cable. Interesting thread. I think we all realize there is the right way and the wrong way to use this cable for feeds. It may also shed light on problems encountered with other cable types. But again, hv cable is used for object in vicinity of cable. If objects are not in vicinity of cable, most anything will do. 

Take care,
Bart





Tesla list wrote:


Original poster: "MIKE HARDY" <MHARDY@xxxxxxxxxx>

Carl Litton was kind enough to respond to this question off-list. He sent me
a pic of 'greenmonster' doing it's spectacular thing. He mentioned you using
xray cable, but failed to tell me you use it with grounded shields in tact.
The way I see it I have 3 choices if I want to use this cable. Do as you do.
Remove the black layer all together, or run it through PVC, or another
suitable insulator. I am very apreciative of all the fascinating discussion
this thread has received.
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Friday, January 06, 2006 11:09 PM
Subject: Re: HV xray cable revisited


> Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
>
> 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
>
>
>
>