[EE] Fake Cable

[Van Horn, David]

I hadn't really thought about this before, and now I'm curious.

I ran across a product which uses some single conductor cable which is marked with their logo and "50kV".
They certainly don't make any sort of wire, so this is something they are having custom marked for them.
I worry that the "50kV" is rather fanciful.

How can I test the insulation of wire, and what exactly causes a wire to be rated for a given voltage?

I've seen 600V power tool wire that's got far more insulation than this stuff, but I can't tell materials by eyeballing it.

Ideas?



--
David VanHorn
Lead Hardware Engineer

Backcountry Access, Inc.
2820 Wilderness Pl, Unit H
Boulder, CO 80301 USA
phone: [phone] x110
email: ***@backcountryaccess.com<mailto:***@backcountryaccess.com>

[a***@stfc.ac.uk]

If it has a polyimide (kapton) insulation it could be quite high voltage cable. One place I worked when I was contracting we got to wondering what the voltage insulation of a piece of kapton self-adhesive tape was, so we stuck a piece to a sheet of aluminium and got out the HV generator probe and had about 8kV (IIRC, certainly well up in the single digit kV) which was the limit of the HV generator without the kapton failing. Other PETE series insulations are related to kapton and could well also have excellent voltage ratings.

I suspect motor vehicle ignition cable is designed for low capacitance to the engine body, which is why it is so thick, instead of using a thinner insulation.

I suspect EHT wire in CRT TV sets is derived from vehicle ignition cable, which is why it is so thick, it is a cheap well understood insulation against a higher cost thinner insulation.

-----Original Message-----
Of Van Horn, David
Sent: 14 August 2017 15:31
Subject: [EE] Fake Cable
I hadn't really thought about this before, and now I'm curious.
I ran across a product which uses some single conductor cable which is
marked with their logo and "50kV".
They certainly don't make any sort of wire, so this is something they are
having custom marked for them.
I worry that the "50kV" is rather fanciful.
How can I test the insulation of wire, and what exactly causes a wire to be
rated for a given voltage?
I've seen 600V power tool wire that's got far more insulation than this stuff,
but I can't tell materials by eyeballing it.
Ideas?
--
David VanHorn
Lead Hardware Engineer
Backcountry Access, Inc.
2820 Wilderness Pl, Unit H
Boulder, CO 80301 USA
phone: [phone] x110
yaccess.com>
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[Van Horn, David]

It's definitely not kapton or silicone. It doesn't look like anything special at all. My bullshit meter is in the yellow when I look at this stuff.


-----Original Message-----
From: piclist-***@mit.edu [mailto:piclist-***@mit.edu] On Behalf Of ***@stfc.ac.uk
Sent: Monday, August 14, 2017 9:12 AM
To: ***@mit.edu
Subject: RE: [EE] Fake Cable

If it has a polyimide (kapton) insulation it could be quite high voltage cable. One place I worked when I was contracting we got to wondering what the voltage insulation of a piece of kapton self-adhesive tape was, so we stuck a piece to a sheet of aluminium and got out the HV generator probe and had about 8kV (IIRC, certainly well up in the single digit kV) which was the limit of the HV generator without the kapton failing. Other PETE series insulations are related to kapton and could well also have excellent voltage ratings.

I suspect motor vehicle ignition cable is designed for low capacitance to the engine body, which is why it is so thick, instead of using a thinner insulation.

I suspect EHT wire in CRT TV sets is derived from vehicle ignition cable, which is why it is so thick, it is a cheap well understood insulation against a higher cost thinner insulation.

-----Original Message-----
Behalf Of Van Horn, David
Sent: 14 August 2017 15:31
Subject: [EE] Fake Cable
I hadn't really thought about this before, and now I'm curious.
I ran across a product which uses some single conductor cable which is
marked with their logo and "50kV".
They certainly don't make any sort of wire, so this is something they
are having custom marked for them.
I worry that the "50kV" is rather fanciful.
How can I test the insulation of wire, and what exactly causes a wire
to be rated for a given voltage?
I've seen 600V power tool wire that's got far more insulation than
this stuff, but I can't tell materials by eyeballing it.
Ideas?
--
David VanHorn
Lead Hardware Engineer
Backcountry Access, Inc.
2820 Wilderness Pl, Unit H
Boulder, CO 80301 USA
phone: [phone] x110
yaccess.com>
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[Sean Breheny]

Can you post a photo of the cross-section of the cable? I've seen HV cable
which had a thin layer of fairly rigid plastic on the outside and some kind
of foam insulation on the inside. I used it at around 35kV and there wasn't
any leakage from the cable and I believe it had a claimed rating of 50kV
and was only about 4mm thick.

On Mon, Aug 14, 2017 at 11:51 AM, Van Horn, David <

Post by Van Horn, David
It's definitely not kapton or silicone. It doesn't look like anything
special at all. My bullshit meter is in the yellow when I look at this
stuff.
-----Original Message-----
Sent: Monday, August 14, 2017 9:12 AM
Subject: RE: [EE] Fake Cable
If it has a polyimide (kapton) insulation it could be quite high voltage
cable. One place I worked when I was contracting we got to wondering what
the voltage insulation of a piece of kapton self-adhesive tape was, so we
stuck a piece to a sheet of aluminium and got out the HV generator probe
and had about 8kV (IIRC, certainly well up in the single digit kV) which
was the limit of the HV generator without the kapton failing. Other PETE
series insulations are related to kapton and could well also have excellent
voltage ratings.
I suspect motor vehicle ignition cable is designed for low capacitance to
the engine body, which is why it is so thick, instead of using a thinner
insulation.
I suspect EHT wire in CRT TV sets is derived from vehicle ignition cable,
which is why it is so thick, it is a cheap well understood insulation
against a higher cost thinner insulation.

-----Original Message-----
Behalf Of Van Horn, David
Sent: 14 August 2017 15:31
Subject: [EE] Fake Cable
I hadn't really thought about this before, and now I'm curious.
I ran across a product which uses some single conductor cable which is
marked with their logo and "50kV".
They certainly don't make any sort of wire, so this is something they
are having custom marked for them.
I worry that the "50kV" is rather fanciful.
How can I test the insulation of wire, and what exactly causes a wire
to be rated for a given voltage?
I've seen 600V power tool wire that's got far more insulation than
this stuff, but I can't tell materials by eyeballing it.
Ideas?
--
David VanHorn
Lead Hardware Engineer
Backcountry Access, Inc.
2820 Wilderness Pl, Unit H
Boulder, CO 80301 USA
phone: [phone] x110
yaccess.com>
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[Van Horn, David]

Interesting.. Whose wire?

I will see if I can get a pic

-----Original Message-----
From: piclist-***@mit.edu [mailto:piclist-***@mit.edu] On Behalf Of Sean Breheny
Sent: Monday, August 14, 2017 10:21 AM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Fake Cable

Can you post a photo of the cross-section of the cable? I've seen HV cable which had a thin layer of fairly rigid plastic on the outside and some kind of foam insulation on the inside. I used it at around 35kV and there wasn't any leakage from the cable and I believe it had a claimed rating of 50kV and was only about 4mm thick.

Post by Van Horn, David
It's definitely not kapton or silicone. It doesn't look like anything
special at all. My bullshit meter is in the yellow when I look at this
stuff.
-----Original Message-----
Sent: Monday, August 14, 2017 9:12 AM
Subject: RE: [EE] Fake Cable
If it has a polyimide (kapton) insulation it could be quite high
voltage cable. One place I worked when I was contracting we got to
wondering what the voltage insulation of a piece of kapton
self-adhesive tape was, so we stuck a piece to a sheet of aluminium
and got out the HV generator probe and had about 8kV (IIRC, certainly
well up in the single digit kV) which was the limit of the HV
generator without the kapton failing. Other PETE series insulations
are related to kapton and could well also have excellent voltage ratings.
I suspect motor vehicle ignition cable is designed for low capacitance
to the engine body, which is why it is so thick, instead of using a
thinner insulation.
I suspect EHT wire in CRT TV sets is derived from vehicle ignition
cable, which is why it is so thick, it is a cheap well understood
insulation against a higher cost thinner insulation.

-----Original Message-----
Behalf Of Van Horn, David
Sent: 14 August 2017 15:31
Subject: [EE] Fake Cable
I hadn't really thought about this before, and now I'm curious.
I ran across a product which uses some single conductor cable which
is marked with their logo and "50kV".
They certainly don't make any sort of wire, so this is something
they are having custom marked for them.
I worry that the "50kV" is rather fanciful.
How can I test the insulation of wire, and what exactly causes a
wire to be rated for a given voltage?
I've seen 600V power tool wire that's got far more insulation than
this stuff, but I can't tell materials by eyeballing it.
Ideas?
--
David VanHorn
Lead Hardware Engineer
Backcountry Access, Inc.
2820 Wilderness Pl, Unit H
Boulder, CO 80301 USA
phone: [phone] x110
yaccess.com>
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[Spehro Pefhany]

The typical material breakdown in volts per mil should be easy to find online if you know the exact material, but pinholes will kill you (perhaps literally in this case).

Personally I think I'd remove those markings.

If you put 30KVDC or so on it and observe it safely in a darkened room you may be able to see purple corona discharge where there are pinholes.

Best regards, SP

Post by Van Horn, David
Interesting.. Whose wire?
I will see if I can get a pic
-----Original Message-----
Sent: Monday, August 14, 2017 10:21 AM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Fake Cable
Can you post a photo of the cross-section of the cable? I've seen HV cable which had a thin layer of fairly rigid plastic on the outside and some kind of foam insulation on the inside. I used it at around 35kV and there wasn't any leakage from the cable and I believe it had a claimed rating of 50kV and was only about 4mm thick.

Post by Van Horn, David
It's definitely not kapton or silicone. It doesn't look like anything
special at all. My bullshit meter is in the yellow when I look at this
stuff.
-----Original Message-----
Sent: Monday, August 14, 2017 9:12 AM
Subject: RE: [EE] Fake Cable
If it has a polyimide (kapton) insulation it could be quite high
voltage cable. One place I worked when I was contracting we got to
wondering what the voltage insulation of a piece of kapton
self-adhesive tape was, so we stuck a piece to a sheet of aluminium
and got out the HV generator probe and had about 8kV (IIRC, certainly
well up in the single digit kV) which was the limit of the HV
generator without the kapton failing. Other PETE series insulations
are related to kapton and could well also have excellent voltage ratings.
I suspect motor vehicle ignition cable is designed for low capacitance
to the engine body, which is why it is so thick, instead of using a
thinner insulation.
I suspect EHT wire in CRT TV sets is derived from vehicle ignition

Interesting.. Whose wire?
I will see if I can get a pic
-----Original Message-----
Sent: Monday, August 14, 2017 10:21 AM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Fake Cable
Can you post a photo of the cross-section of the cable? I've seen HV cable which had a thin layer of fairly rigid plastic on the outside and some kind of foam insulation on the inside. I used it at around 35kV and there wasn't any leakage from the cable and I believe it had a claimed rating of 50kV and was only about 4mm thick.

Post by Van Horn, David
It's definitely not kapton or silicone. It doesn't look like anything
special at all. My bullshit meter is in the yellow when I look at this
stuff.
-----Original Message-----
Sent: Monday, August 14, 2017 9:12 AM
Subject: RE: [EE] Fake Cable
If it has a polyimide (kapton) insulation it could be quite high
voltage cable. One place I worked when I was contracting we got to
wondering what the voltage insulation of a piece of kapton
self-adhesive tape was, so we stuck a piece to a sheet of aluminium
and got out the HV generator probe and had about 8kV (IIRC, certainly
well up in the single digit kV) which was the limit of the HV
generator without the kapton failing. Other PETE series insulations
are related to kapton and could well also have excellent voltage ratings.
I suspect motor vehicle ignition cable is designed for low capacitance
to the engine body, which is why it is so thick, instead of using a
thinner insulation.
I suspect EHT wire in CRT TV sets is derived from vehicle ignition
cable, which is why it is so thick, it is a cheap well understood
insulation against a higher cost thinner insulation.

-----Original Message-----
Behalf Of Van Horn, David
Sent: 14 August 2017 15:31
Subject: [EE] Fake Cable
I hadn't really thought about this before, and now I'm curious.
I ran across a product which uses some single conductor cable which
is marked with their logo and "50kV".
They certainly don't make any sort of wire, so this is something
they are having custom marked for them.
I worry that the "50kV" is rather fanciful.
How can I test the insulation of wire, and what exactly causes a
wire to be rated for a given voltage?
I've seen 600V power tool wire that's got far more insulation than
this stuff, but I can't tell materials by eyeballing it.
Ideas?
--
David VanHorn
Lead Hardware Engineer
Backcountry Access, Inc.
2820 Wilderness Pl, Unit H
Boulder, CO 80301 USA
phone: [phone] x110
yaccess.com>
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[Sean Breheny]

I found it here:

http://www.belden.com/techdatas/english/8868.pdf

My memory was wrong - it is rated 24kV. I may have been using it beyond its
rating.

Sean


On Mon, Aug 14, 2017 at 12:23 PM, Van Horn, David <

Post by Van Horn, David
Interesting.. Whose wire?
I will see if I can get a pic
-----Original Message-----
Sent: Monday, August 14, 2017 10:21 AM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Fake Cable
Can you post a photo of the cross-section of the cable? I've seen HV cable
which had a thin layer of fairly rigid plastic on the outside and some kind
of foam insulation on the inside. I used it at around 35kV and there wasn't
any leakage from the cable and I believe it had a claimed rating of 50kV
and was only about 4mm thick.

Post by Van Horn, David
It's definitely not kapton or silicone. It doesn't look like anything
special at all. My bullshit meter is in the yellow when I look at this
stuff.
-----Original Message-----
Sent: Monday, August 14, 2017 9:12 AM
Subject: RE: [EE] Fake Cable
If it has a polyimide (kapton) insulation it could be quite high
voltage cable. One place I worked when I was contracting we got to
wondering what the voltage insulation of a piece of kapton
self-adhesive tape was, so we stuck a piece to a sheet of aluminium
and got out the HV generator probe and had about 8kV (IIRC, certainly
well up in the single digit kV) which was the limit of the HV
generator without the kapton failing. Other PETE series insulations
are related to kapton and could well also have excellent voltage ratings.
I suspect motor vehicle ignition cable is designed for low capacitance
to the engine body, which is why it is so thick, instead of using a
thinner insulation.
I suspect EHT wire in CRT TV sets is derived from vehicle ignition
cable, which is why it is so thick, it is a cheap well understood
insulation against a higher cost thinner insulation.

-----Original Message-----
Behalf Of Van Horn, David
Sent: 14 August 2017 15:31
Subject: [EE] Fake Cable
I hadn't really thought about this before, and now I'm curious.
I ran across a product which uses some single conductor cable which
is marked with their logo and "50kV".
They certainly don't make any sort of wire, so this is something
they are having custom marked for them.
I worry that the "50kV" is rather fanciful.
How can I test the insulation of wire, and what exactly causes a
wire to be rated for a given voltage?
I've seen 600V power tool wire that's got far more insulation than
this stuff, but I can't tell materials by eyeballing it.
Ideas?
--
David VanHorn
Lead Hardware Engineer
Backcountry Access, Inc.
2820 Wilderness Pl, Unit H
Boulder, CO 80301 USA
phone: [phone] x110
yaccess.com>
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[Harold Hallikainen]

It's also fairly common to use coaxial cable for high voltage. Some pretty
high voltages are shown at
http://montoya.sdsmt.edu/ee483/handouts/RG_coax_list.pdf . A nice thing
about coax is that if it does break down, it breaks down to the shield
instead of to the person touching the cable.

Harold

[Art]

Hi Alan et al,

Motor vehicle ignition cables and EHT wire in the old fashioned TV's are
bigger than they have to be, by far. However, longevity is the reason.
Both have to last for years without failing due to environmental
concerns/extremes. The include, but aren't limited to, high humidity,
temperature extremes, airborne pollution, ozone exposure and abrasion.

I think that any insulation that has a higher dielectric constant than
air (all insulators do) actually increases the capacitance between the
conductor and the engine block.

Today we have fake 'everything' and it does kill.

Regards,

W1ABA

Post by a***@stfc.ac.uk
I suspect motor vehicle ignition cable is designed for low capacitance to the engine body, which is why it is so thick, instead of using a thinner insulation.
I suspect EHT wire in CRT TV sets is derived from vehicle ignition cable, which is why it is so thick, it is a cheap well understood insulation against a higher cost thinner insulation.

[Van Horn, David]

I suppose I could put it through a foot of copper pipe and measure leakage. Ground the pipe and measure capacitance might tell me the dielectric constant and therefore the insulation material.
I don't have a high voltage DC supply in this range, other than a VanDeGraff which is pretty uncalibrated.

I know that wire insulation frequently performs well beyond it's spec, so detecting bogus wire might be a challenge.

[Chris McSweeny]

Post by Art
I think that any insulation that has a higher dielectric constant than
air (all insulators do) actually increases the capacitance between the
conductor and the engine block.

Only if the separation between the conductor and the engine block remains
the same. If the insulator is in contact with the engine block and keeping
the conductor away from it then a thicker insulator will increase the
separation and reduce the capacitance (if there is also an air gap then the
dialectric constant of the insulator is likely to be irrelevant as the
capacitance will be negligible).

Chris

[Van Horn, David]

I've been reading up, and the construction of high voltage cabling is pretty interesting.
Special semi-conductive anti-corona layers.

Have a look at "Magnecor" spark plug wire.

Spiraling the center conductor may simulate a larger diameter conductor for corona prevention, while maintaining the flexibility of the tiny center conductor.
330 ohms per foot, but I suspect the DC R is relatively trivial in this application. Coils with outputs of a few amps during the pulse have significant impedance in themselves, and once ignited the spark is essentially a short.


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[Van Horn, David]

So is there a simple(?) test that I can apply to prove or disprove cable insulation ratings?

Partial discharge test comes to mind, but "all" I need is a quiet 50kVDC source, some coupling caps and an input circuit that will stand the voltage, and a scope and a test fixture.

[Sean Breheny]

I would guess that a combination of:

Wrap foil around the outside and measure leakage between cable conductor
and foil at full anticipated voltage (plus maybe some excess voltage)
Apply full voltage, turn out the lights, and look for corona

would be a good start but I could see a cable passing those tests but then
failing when flexed while carrying HV or even just failing after a year or
two due to small amounts of internal corona in insulation voids leading to
chemical breakdown of the insulation from ozone generation.

On Thu, Aug 17, 2017 at 11:43 AM, Van Horn, David <

Post by Van Horn, David
So is there a simple(?) test that I can apply to prove or disprove cable
insulation ratings?
Partial discharge test comes to mind, but "all" I need is a quiet 50kVDC
source, some coupling caps and an input circuit that will stand the
voltage, and a scope and a test fixture.
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[s***@agilent.com]

A kite and a thunderstorm? Do you have any friends called Ben? ;o)


-----Original Message-----
From: piclist-***@mit.edu [mailto:piclist-***@mit.edu] On Behalf Of Van Horn, David
Sent: Friday, 18 August 2017 1:43 AM
To: Microcontroller discussion list - Public. <***@mit.edu>
Subject: RE: [EE] Fake Cable

So is there a simple(?) test that I can apply to prove or disprove cable insulation ratings?

Partial discharge test comes to mind, but "all" I need is a quiet 50kVDC source, some coupling caps and an input circuit that will stand the voltage, and a scope and a test fixture.


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