From: "Barton B. Anderson"
Date: Thu, 23 May 2002 20:20:11 +0000
Subject: Re: [TSSP] Topload breakout potentials
Hi Paul - Hey, I found the issue with my cap (and it's "not" temp or humidity). The cap "is" 65nF (and I would say close to this value as I saw it flicker once or twice between 64 and 65, meaning it's at the upper end of 64nF and rested at 65nF). BTW, my cap is not MMC. It is comprised of three 20nF caps in parallel. These are professional pulse polystyrene 60kV caps made by CSI in CA. I've never got them even warm. Connection to the primary and ground (parallel or series) showed 65nF. However, it measures 61nF when the transformer and ground are connected. Thus, the transformer is what was throwing it off (I measured a couple nF across the transformer and ground). I obvioulsy had this connected during my early measurements. So, that settles that. Paul wrote: > > The cap measured 65nF tonight. > > Thanks, that fits then. That's quite a change in Cpri. > Is it an MMC? Perhaps there's a dry joint on one of the > strings which is coming and going? > > Anyway, everything about your coil's tuning adds up now, and > fits with the model. > > Interesting that your MCTV would give 40.1kV/cm at the surface > but the 12% detune just happens to bring that down to 26kV/cm. > Is that a coincidence? Eeeek! What are the odds? > Working the other way now, if we take Bart's > -12% offset tuning, that would need an extra 10pF of streamer > loading to drop the secondary Fres down to match (do you have > two at 5 foot?). Yes, I've had two streamers at about 5 feet. Not always, the coil toggles between streamers, and while there are 1 or 2 main streamers, there are others which have broke out elsewhere and giving up their energy. It seems that one area will breakout before another area has completely gone away. Everything happens so fast, it takes a while before I can really see the average breakout reaction of streamers. > Those streamers hold an energy > 0.5 * 10pF * 590kV^2 = 1.7J which is all that remains of the > primary's initial reserve at breakout of 9.4J. > > So how're we going to measure topvolts now? I don't know how, but we've got to figure out a way. Seems this is where we always get stuck. Ibase measurements should be no problem and easy enough. I've decided to purchase a hf current sensor (Digikey has one well within our frequency range). It's the top volts which stumps me. How do power company's measure those big kv lines? Bart
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.