[TCML] Corona Supression
brandonhendershot at gmail.com
Mon May 17 10:03:11 MDT 2010
So is there anything like "corona dope" inexpensive enough to be
applied and removed whenever I need to take things off the terminals?
Does corona dope or glyptal need to under vacuum to be applied?
On May 16, 2010, at 9:12 PM, jimlux <jimlux at earthlink.net> wrote:
> Brandon Hendershot wrote:
>> I got a few bolts used as terminals I'd like to cover up. Some
>> other structural nuts and bolts running close to wires I'd like to
>> get some extra assurance on as well. I figured a round cap nut
>> ought to suffice, but I prefer the idea of sticking on some rubber
>> Any kind of rubber caps good for HV? I remember seeing something
>> pretty fitting of the description in the hardware section down at
>> home depot. It looked way too thin though...
> rubber caps will be worthless... if there's any air gap at all
> between the metal surface and the rubber, you'll get corona in
> there, and it will rapidly degrade the rubber into dust/mush.
> Corona is all about radius of curvature.
> If you want to cover it with an insulator, you need something that
> conformally coats it. Corona Dope or Glyptal are the classic
> century old approaches.. kind of a runny plastic dissolved in a
> volatile solvent, so it coats well, without leaving gaps. SIlicone
> is popular today, but tricky, because you really have to do it under
> a vacuum, so that tiny air bubbles don't form. Bubbles create field
> concentrations, which cause corona inside the bubbles, which causes
> dielectric "treeing", which results in breakdown (mechanical and
> electrical, both).
> You begin to see why liquid or gas insulators are so nice... plunk
> it in the tank of oil, pull a bit of a vacuum to get the bubbles
> out, and you're done.
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