From: Bert Hickman
Date: Sun, 27 Oct 2002 23:44:40 -0600
Subject: Re: [TSSP] Top Voltage
Hi Boris and all, boris petkovic wrote: > Hi Paul,All, >> I'm glad to hear there's a large amount of avilable > publications on the subject.Surely,that is helpful. > But something bothers me.Bert and Marco both mentioned > there was concentration in the papers just on positive > discharges.How come?What's that special about positive > electrode over negative one?I remind others that we > need both polarities succesive waves effects to > examine in detail. We're pretty much stuck with what's in the literature. For nonuniform gaps, long sparks propagate more easily when the active electrode is positive (i.e., cathode-directed streamers). This is of great importance for determining appropriate minimal air clearances for HV Power transmission and other HV applications, so it forms the core of much HV Power research. On the other hand, a good portion of lightning research involves negative (anode-directed) streamers, since most cloud-to-ground lightning originates in the lower (negatively charged) cloud base. However, lightning protection studies actually involves both negative and positive streamer/leader propagation, since positive leaders rise from the tips of high objects right before they connect with a descending negative leader to form a main stroke. Unfortunately, the rapid polarity reversals seen in a Tesla Coil are simply not very common in lightning research or in power distribution. So, unfortunately, there's not a lot of research material available, or being done, for long RF sparks. > Maybe ,it is too early to consider leader(s) > development stages,or even corona-leader ignition > phenomena ,since we haven't got straigtened even > avalanche-streamer transition stage in case of OLTC, > but oscillating nature of TC wave in early stages of > gas excitation might have influnce to latter more > powerful events too. I agree... the successive stages of corona, corona streamers, and leaders constitute a natural progression if increasing intensity as terminal voltage increases. However, complex interactions between increasingly higher terminal voltage oscillations and space charges left over from previous polarity excursions makes analysis extremely challenging... > Speaking of which,how is ceiling construction progress > ,Terry? > Paul,despite what you think that first we should take > some time to study avilable publications before > serious experimentation/msms on OLTC,I think some > preliminary scoping tests under obvious breakout would > come in handy.Only problem here is the requirement of > the high precision of scoping.We should be looking > for a very small changes in Fr (say 0.1 %) due to > possible presence of low energy loading (single pulse > mode meant ,of course). > --- > >>I begin to >>see now why breakrate, frequency, and coupling will >>have a big >>impact on the breakout. > > --- > Yes.The sea of varitions there. > --- > > > >>there and some effort will be required to filter out >>the relevant >>bits without drowning in information and getting >>hopelessly lost. > > --- > Huh..I agree. > --- > > >>Hopefully, we can achieve our aims without having to >>do any >>original research of our own. We can continue our >>tradition of >>working from well established physical principles - >>no need to >>launch off into the dark. > > --- > I'll be happy if the mentioned outcome will be > reached. > However,nobody before have studied seriously impulsive > gas discharges of Tesla coils at academic level. > And no wonder knowing all the difficulties associted > with this task. And, unlike HV power transmission or lightning protection, there's not a huge economic need to get answers to Tesla Coil spark propagation questions... :^) > > --- > > > >>To summarise our goals as a guide to what info is >>relevant: >> >>Our good understanding of the secondary needs to be >>extended >>to account for the interaction with breakout >>loading. We would >>like to be able to predict the breakout performance >>of a TC, >>given the geometry and firing voltage.[*] > > --- > You see what I mean.As of now,we are stucked already > in first step.Not to mention what comes later.. > Hope the things will change for better soon as > concerns first step.Than we'll give a thought of how > to proceed with next step. > --- > > >>Predicting the performance, in this sense, means >>being able to >>estimate the typical number and length of inhibited >>leaders when >>discharging into air, for a given firing voltage. > > --- > Ah,this would be the last step.Still a long way to > come to it. > --- > > > >>To do so, we will likely have to take account of the >>dynamically >>varying load applied to the secondary, working in >>the time domain >>to derive a numerical solution to the non-linear >>system. Only then >>will we cope with arbitrary topload waveforms (wide >>range of Ctop, >>Fres, and k). > > --- > Bottom line is that slight variations in Fr of > secondary could be present without any inhibited > leader attached to a terminal. > ---- > > We'll > >>just have >>to see how things come out. > > --- > Usual modus opearandi of an every research . > --- > >>I'll start a new web page this weekend to summarise >>existing >>applicable research on breakout phenomena. I'll use >>it to keep >>track of which references we need to obtain or have >>got, so that >>Marco will know exactly what to go for. > > --- > Very good. > > regards, > Boris > > __________________________________________________ > Do you Yahoo!? > Y! Web Hosting - Let the expert host your web site > http://webhosting.yahoo.com/ > Best regards, -- Bert -- -- Bert Hickman Stoneridge Engineering "Electromagically" (TM) Shrunken Coins! http://www.teslamania.com
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.