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Would this wire be good for HV?

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lpfthings

Fri May 02 2008, 10:17PM

Registered Member #1361 Joined: Thu Feb 28 2008, 10:57AM
Location: Cairns, Australia
Posts: 305

Wire with lots of insulation for HV stuff isnt easy to come by around here, but basically i have some wire that looks like it may work. It's the stuff you use to hook your aerial to the TV (cant remember it's name, sorry). It looks like it has a fair amount of insulation, and seems to have a signle copper wire through the middle. Would this work on my NST? I just need some wire that wont arc through if they are near each other.

Arcstarter

Fri May 02 2008, 10:28PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Well i don't know how the insulation is but i know that since it is close it will arc through due to ozone after awhile. Also, it has some capacitance which will put extra load on the nst which means somewhat less power output.

Antonio

Fri May 02 2008, 10:40PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

This is probably a 75 Ohms coaxial cable, with a central wire and a mesh around. Look at the insulation around the central wire. If it is a kind of foam, and not a thick solid plastic, the cable is useless. Anyway, the safe way to make high-voltage circuits is to not let the wires touch anything. You can then use any wire. Just avoid sharp curves.

lpfthings

Sat May 03 2008, 12:19AM

Registered Member #1361 Joined: Thu Feb 28 2008, 10:57AM
Location: Cairns, Australia
Posts: 305

OK, well the cable is the stuff they use for satellite TV, but same stuff i guess. It seems to be hard plastic around the central wire. The only problem i see is that would HV build up in the sheilding wire? I am just looking for a thick cable, for when i'm experimenting. if the wire is to thin, it arcs through, sets the insulation on fire and results in toxic fumes.

jpsmith123

Sat May 03 2008, 12:41AM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

IIRC, some people are successfully using RG8-U coax cable at voltages as high as 40 kv dc.

Andyman

Wed May 07 2008, 05:11AM

Registered Member #1083 Joined: Mon Oct 29 2007, 06:16PM
Location: Upland, California
Posts: 256

Just get a bunch of vinyl tubing from your hardware store and put the wire inside. I've tested it up to 13 kv and I can hold the wire in my hand with only a teenie bit of corona.

Mates

Wed May 07 2008, 05:35AM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

Andyman wrote ...

....I can hold the wire in my hand with only a teenie bit of corona.

Hand touch - that's "really clever" way of testing how good your isolation is

Otherwise you right - the PVC tubing will do the job, you can even adopt part of the protocol for this HV diode

and fill the tube with oil...

Dago

Wed May 07 2008, 08:41AM

Registered Member #538 Joined: Sun Feb 18 2007, 08:33PM
Location: Finland
Posts: 181

Andyman wrote ...

Just get a bunch of vinyl tubing from your hardware store and put the wire inside. I've tested it up to 13 kv and I can hold the wire in my hand with only a teenie bit of corona.

That sounds extremely dangerous, I hope you arent using a high-current PSU to do that...

johnf

Fri May 09 2008, 07:38AM

Registered Member #230 Joined: Tue Feb 21 2006, 08:01PM
Location: Gracefield lower Hutt
Posts: 284

Since you are in Australia go to your local Dick Smith store or Jaycar and buy RG8 also known as UR 67 or RG 213 we use these cables at work up to 100kV make sure that you pair back the braid for several inches (12" for 100kV) so that the ends dont arc over.
If your PSU is DC remember that the cable is also a capacitor at around 100pf per foot so it can store a nasty charge after you have switched off.
Solid polyethylene dielectric only no foam filled low loss cables are suitable the above part numbers are the solid kind.

RG11 is also alright

quicksilver

Fri May 09 2008, 02:06PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

In the USA I've heard of quite a few people say that RG8-U coax cable worked well up to a point. You may have a good response with a NST because the central cable shielding is really quite well insulated and if you're not dealing with a greater level of current than 30ma it may be fine. The best thing is to test it and see. I was thinking of just the same thing.

But I would NOT test HV materials with my body. Aside from everything safety issue already mentioned; it's not that good of a test! I once saw someone use a "C" clamp test meter away from a cable that he had bent in a "U" shape and hold the meter out from the junction of the bend to test the shielding. There are much more effective ways of determining shielding properties of course. Actually since Australia has the higher current/voltage standard there may be some very good research published on the internet dealing with that subject from a variety of public or industrial agencies.

I've been shocked a few times in my life but the first time I really got one was determined to be my last. I had gotten complacent with the 120Vac in the USA & generally gotten zapped from stuff that was reduced by household appliances that acted with resistance so basically I THOUGHT that main current was pretty tame. I was also in my twenties and thought I was invulnerable.

The one day I backed into a poorly protected 240 input for a welder. It just hit my elbow....I think. I really don't remember much except getting thrown across a shop like Godzilla's old beer can. What I DO remember was that I could hardly catch my breath. I was 25 and running tri-athalons. I think today that would have shut me down & killed me.

I have too much respect for HV to touch test anything anymore. Once you get bitten by the REAL thing, the reaction is VERY different than you ever though it could be. Please ...be careful.

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