Re: Partial Discharges.....A good reason for cap failure?

To: tesla-at-pupman-dot-com
Subject: Re: Partial Discharges.....A good reason for cap failure?
From: "Jim Lux" <jimlux-at-jpl.nasa.gov> (by way of Terry Fritz <twf-at-verinet-dot-com>)
Date: Sun, 07 Mar 1999 19:32:55 -0700
Approved: twf-at-verinet-dot-com

> Jim,
> Could you tell me which file you are referring to? I downloaded
> your site a while ago and did an offline search on the files I have
> (maybe you added something to your website?), but couldn´t
> find what you mentioned. I think I have the idea, I just want to be
> sure of it. Thanks.

Nope, not on the site.. It is in Khalifa, ed. High Voltage Engineering, as
well as some other text books. Actually, the scheme mentioned on the list
recently using an AM radio as a corona detector would probably work quite
nicely. 

But, in my case, the idea would be to use a series C of a few 10s of pF
feeding a load resistor of a few K. The scope measures the voltage across
the resistor (basically, building a RC differentiator (or HP filter)). Time
constant is something like a few microseconds. On the commercial units, I
think they use the line voltage as the horizontal input, and the output of
the differentiator as the vertical input. It gives you an elliptical trace
(lissajous figure) with "vertical grass" when the discharges occur. I
gather from my reading ( I haven't actually used one of these devices) that
there is a whole art to the interpretation of these pictures.

>