If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
dam it!, i was afraid you were going to say something like that radiotech. i was fearful that the current limit shunts would drive the math/physics to less than ideal, indeed much less than linear/ideal. And lets all remember that NST's are much different in internals compared to other sine transforemers.
i guess i have to find a PT. let me cruise ebay.
EDIT: from low to high on A and B i get 1.8% and 1.6 % apparent deviation from a constant 53:1 turns ratio. but i only need a single constant voltage and they seem stable and repeatable for calibrating my CVD.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
radiotech wrote ...
If the ratio error was caused by transformer distorting waveform do do need to know this for calibration purposes?
I dont think so !? I will be using an O-scope, not an RMS averaging DMM.
pics too follow: top: "cheap" o-scope (200$) for hazard duty only. middle: neon protection device as per your advice Radiotech. ignites @ 49VAC, holds off / extinguishes @ 48VAC bottom: also seen here, castin' craft filled resistors, I love this stuff. Also, i'm totally drunck right nowe.
Remember per FAA rules, 8 hours between bottle and throttle peeps. This is my NST its a "Franceformer". original nameplate broke off so i labeled it again.Seen abuve the yellow writing is dykem paint marker and only temporARY.
how there mAde. polyurethane epxoy. The 61.21M resistor out of its PEX sleeve.
epoxy cast of Xicon common carbon comp resistors, there rated for 500V, 10M, 0.25 Watt at 5%. i try not to exceed the 500V limitation, even with the epoxy. i think i still have 1,100 left.
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
For calibration- consider how the specification will read. Will the next user get the same numeric result if their voltage wave is different.
rated for 500V, 10M, 0.25 Watt at 5%. i try not to exceed the 500V limitation,
Try and find to the standard the manufacturer used to rate these. The voltage rating for carbon composition resistors of various wattages is Peak volts/length.
Hard to know the layout of the circuit board of your resistor chains but given the voltage is dropped in discrete "chunks", having resistors on top of each other isn't good. If you have X meters of resistors they should laid out for equal volts/meter. Take a look at the layout of the NBS 100kV resistor in the portion of the paper sent before. What we always consider in high voltage gear if constant potential gradient, the reason being if corona, or pre-corona is present, it should load linearly. If it doesn't, then the voltage drop isnt linear. In that paper they do mention that leakage errors are checked by seeing if the current going into the resistor is the same as what comes out. Who said the HV has seem to obey ohm's or Kirchoff's laws. In the real world, a crappy layout or insulation job will fail and cause darkness.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
radiotech wrote ...
rated for 500V, 10M, 0.25 Watt at 5%. i try not to exceed the 500V limitation,
Try and find to the standard the manufacturer used to rate these. The voltage rating for carbon composition resistors of various wattages is Peak volts/length.
the standard may be hard to find, i may have to call them.
radiotech wrote ...
Hard to know the layout of the circuit board of your resistor chains but given the voltage is dropped in discrete "chunks", having resistors on top of each other isn't good. If you have X meters of resistors they should laid out for equal volts/meter. Take a look at the layout of the NBS 100kV resistor in the portion of the paper sent before. What we always consider in high voltage gear if constant potential gradient, the reason being if corona, or pre-corona is present, it should load linearly. If it doesn't, then the voltage drop isnt linear. In that paper they do mention that leakage errors are checked by seeing if the current going into the resistor is the same as what comes out. Who said the HV has seem to obey ohm's or Kirchoff's laws. In the real world, a crappy layout or insulation job will fail and cause darkness.
i belive the construction was made with good layout, i wish i had a E-field simulator, but the resistors are 10M, there are 3 on top of each other in parallel for ~3.4M then those clusters of 3 are zig-zagged to keep the voltage drop linear (from end to end) in 420Vrms drop steps, so i belive i have used good practices. i would prefer to use special HV resitors but i would have no way to accuratelly measure them as i do not have a giga-ohm-meter.
At 420Vrms a wave does reach 594Vp-p for a few pecent of the sine wave. so i have violated that 500V limitation.
will post pic:pics does this help radiotech? i yhink i did all this right, i didnt want unequal voltages in adjacent solder nodes or body lengths of resistors nearby. i belive as seen in the pics you provided i did what they did minus the helix part.
i suppose i could make them with out the zig-zag but instead of 7.3 in. long they would then be 16 in.long in PEX tube.
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
Here's the approach some meters like the Fluke 87 use to extend the resistance to 100,000 Megohms. I scannel the book from mine. Another old trick is to connect a battery, 9 or 22.5, Volts in series with the resistor, then measure its resistance. Do the math first.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
SH*T: your right radio tech i have a leakage issue, that paper you posted makes more sense now. im leaking 24uA from the 108V lo and 108V hi measurement. im leaking 33ua from the 146V lo and 146V hi measurement. ive made changes to improve corona resistence, now its almost noise free, i see what you mean about kirchoff dam it. all i can say is that i wonder what to do now. dam it all accuracy from the above calcs is worthless, im missing almost 20-25% of my current.
ok, (total current in)-(current loss out) = current in the 61.21Mohm resistor.
i calculate about 11 T ohms of resistence through the polyurethane, soo... 10 kV / 11T = 1nanoAmp so i be sure thats less relevant. im confident in the 61.21 Mohm quaantity, let me now check the chemical / physical sources.
EDIT: the leakage rate seems consistant and predictable so far, i think the "lost energy" is going toward ozone / heat / UV as per the law of conservation.
after eliminating as much leakage as possibe i found the high side measurement of current too be more accurate, well... i think. since the resistor is now grounded with no resistence from the current meter between it and ground.
i dont know if this is possible anymore, i may just have to settle for a PT if i can get one. alot of the PT's on ebay say this: 10 KV.BIL.0.6KV.CL what does this mean?
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
BIL basic impulse level The rating for maximum volts, (tests for when a line is hit by lightning)
Table 7 Nominal System Voltage is the phase tp phase voltage and line to ground is the Y leg voltage. Yours is 277 volts which comes from a phase to phase system of 480 volt. (1.73 *277) I believe they used 0.6 kV because there is no entry for 480 volts in the standard. If you look at Fig 2 above you get some idea of ratio correction factors for various loads at various power factors. from ANSI C57.13-1978. (the spec must lie within the parallelogram)
277 volt systems are found in some buildings for lighting. Half asleep electricians have been known to accidently install 120 volt balasts in 277 volt fixtures. They last of 20 seconds.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
radiotech wrote ...
277 volt systems are found in some buildings for lighting. Half asleep electricians have been known to accidently install 120 volt balasts in 277 volt fixtures. They last of 20 seconds.
oops when i was a guest speaker at a high school an electrician drilled through a cement filled cinder block wall, hit a main incoming 480 volt line in an EMT conduit, 200A @ 480VAC is quite loud, we were with out power for 3 days of that week.
ok, i see what you mean on the table below the graph which starts at 0.6 kV
so now, "ACC 0.6W 1.2X" what does that mean? from your scan maybe the 0.6W is the a accuracy class? but then whats the "1.2X" ? also, i cant find anything on the instrument transformers inc. company, so i dont know if i should buy it or not.
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
From the standard : 7.3.1 " A voltage transformer shall be assigned an accuracy rating for each of the standard burdens for which it is designated .For example, an accuracy rating might be 0.6W and ....1.2 X...... (see the parallelogram)
for 120 Volt.. burdens are
X is 25 VA 0.70 PF 403.2 ohm resistance 1.09Hy. 576 ohm impedance..(characteristics at 120 volt) W is 12.5 VA 0.10 PF 115.2 ohms R 3.04 Hy 1152 ohm impedance
and another set of numbers for 69.3 Volts
Try and get the standard; from page 9 to 43 is all the stuff on PT's. Schools can get it from IEEE if they pay the 'standard subscription'
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
Potential Transformers, HV measurement.
I will be using an O-scope, not an RMS averaging DMM. 
when i was a guest speaker at a high school an electrician drilled through a cement filled cinder block wall, hit a main incoming 480 volt line in an EMT conduit, 200A @ 480VAC is quite loud, we were with out power for 3 days of that week.