From: "Terrell W. Fritz"
Date: Wed, 04 Aug 2004 16:39:28 -0600
Subject: Re: [TSSP] Secondary dynamic Efield
Hi Marco,
I was going to actually shield the darn thing and insulate it all with
oil... A long lost project...
Stray capacitance is the real killer. But I was going to use copper ground
shields to protect the sensitive dividers with a known stable capacitance
to ground. Lots of copper sheet and lots of oil...
I can "conjure" up the details if needed... I just stole all the ideas
from a Jennings RF 60kV vacuum voltage divider I got off E-bay....
Watch out for voltage stresses that cause breakdown off sharp edges!!! I
think that is what got mine all bogged down... Even under oil, voltage
stress and breakdown is a real big deal for a divider that works at say
500kV... Big radiuses and all that are needed... I "giant" vacuum divider
would be super cool if you have a glass/vaccum shop...
Cheers,
Terry
At 02:21 AM 8/4/2004, you wrote:
>Hi Paul,
>
>I'm getting acquainted with HV resistive dividers. I tested my first one
>and got proof of its poor performance. What actually spoiled it was its
>10 pf stray capacitance to GND. I got a step response of 30 us (!). Some
>would say easy to guess for a resistance of 1.2 Mohm.
>
>Hanging the divider at 3 m height will sure reduce its capacitance to
>gnd. That was my original plan. But now I learnt that any discontinuity
>in the Efield even AROUND its water column will result in unbalanced
>stray capacitance and, therefore, in slow step response.
>
>I'm reluctant to place the divider inside the secondary because it's
>difficult to mount it and service it there. But there the Efield should
>be pretty constant. But... Now comes my question.
>
>If I recall you and Terry produced some nice dynamic plots of the
>secondary voltage and current. Wasn't it so that they were varying at
>the secondary frequency? That would imply not constant dynamic Efield
>distribution inside the secondary and make the probe placement there
>definitevely a bad idea. Am I right?
>
>Best Regards
>
>
>
>
>
>
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Maintainer Paul Nicholson, paul@abelian.demon.co.uk.