Re: RG-213 cable core as hv cable? (fwd)

[<sroys@xxxxxxxxxxxxxxxxx>]

---------- Forwarded message ----------
Date: Fri, 12 Nov 2004 11:55:30 -0800
From: Jim Lux <jimlux@xxxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: RG-213 cable core as hv cable? (fwd)


>Date: Thu, 11 Nov 2004 13:39:46 -0500
>From: Jack Vandam <snotoir7674g@xxxxxxxxxxxxxx>
>To: High Voltage list <hvlist@xxxxxxxxxx>, hvlist <hvlist@xxxxxxxxxxxxxxxxx>
>Subject: RG-213 cable core as hv cable?
>
>I wanted to ask the group about this.  Several years ago, I remember reading
>somewhere that the polyethylene  surrounding RG-213 coaxial cable could
>withstand up to 40 KV(?) in high voltage applications as long as the shield
>and outer jacket were removed.  Can anyone confirm this?
>
>Thanks,
>Jack

yes and no.

The HV rating is higher with the shield on (it ensures the field is even), 
and the shield provides a safety measure: if the insulation fails, it arcs 
to ground (through the shield) not through something else (like the 
surrounding equipment).

You can also use modified UHF (PL-259/SO-239) connectors with this size cable.
I've used it at 30kV (RMS 60Hz), and you see an awful lot of it 
around.  What I didn't check was whether the insulation is slowly degrading 
at that voltage (it probably is... there's probably little microcracks and 
treeing developing).


The actual cable was designed for continuous working voltage of 3700Vrms or 
about 5kV peak.  However, there is a fair amount of design margin, and, you 
generally ask for a factor of two in addition (in case there's reflected 
waves.. the voltage might be twice).

The PE dielectric is 0.285"OD, however a simple V/mil calculation won't do 
it because the field's not uniform.

The mfr test process requires it be tested for Voltage Withstanding to 
10,000V RMS +10%,-0% and have a corona extinction voltage of 5000Vrms minimum.

(all this from MILC17-74)

By the way, there is no such thing as RG-213/U any more.  It's been 
discontinued as a spec (DoD doesn't buy polyethylene insulated wire any 
more due to fire hazard), so all you really can get is:
"manufactured to meet (cancelled) MIL STD-c-17-74 RG/213"
or
"RG-213 type"

and other circumlocutions.