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Joined: Jan 2010
Posts: 6
E
New Member
Where do you see anything disrespectful ??????

Arc Flash PPE Clothing, LOTO & Insulated Tools
Joined: Jul 2002
Posts: 8,443
Likes: 3
Member
Originally Posted by electricsquirrel
Where do you see anything disrespectful ??????

Could it be this?, maybe:
Quote
I'm not going to start an argument here,BUT UNLESS you have ACTUALLY ever worked on high voltage under ground or overhead lines you are NOT qualified to tell me how it works!

And by the way, don't use All Caps, it sounds like you are shouting, it is also rude.

Last edited by Trumpy; 01/25/10 02:21 AM. Reason: Typo
Joined: Jan 2005
Posts: 5,445
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Cat Servant
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I think I have something to contribute here.

I've done bench test testing of gear for a major testing lab, and one of the tests involves applying high voltages to terminals in equipment. If they're too close together, or the barriers aren't adequate, you can see the arc jump across the space from one terminal to another. Why do you think 480v gear is so much larger than 240v gear if the same amperage rating?

Likewise, I have seen the reasonably high voltage created by a car's HEI coil run along the surface of the coil wire, then jump across the 1" (or so) distance through dry air to make contact with a rubber fuel line.

There are also a number of documented PoCo accidents, where an arc jumped between substation gear when equipment, or personnel, filled the space between things. Oops.

Then there's everyone's favorite science project, the Jacob's ladder. Mine was making 3" arcs before it broke; the arcs started by jumping a 3/4" distance.

That electricity can jump distances, and that the distance is dependant upon voltage, is pretty basic science.

As for qualifications ... I'm not impressed. I never have been. An argument ought to be able to stand on it's own merits; ever great discovery was made by a nobody - Newton and Einstein were 'nobodies' when they put forth their theories. The "Greats" of their days are now largely forgotten.

ECN is fairly unique in the internet world, in that it has a great variety of professionals here. Master electricians to handymen, associated trades like engineers, linesmen, and inspectors.

And that's the key; "associated" trades, rather than any sort of system of 'rank.' I am endlessly amused at the ignorance of folks who think an engineer 'outranks' an electrician. That's a lot like expecting a 'mechanical engineer' to fix your car. Lots of luck with that!

I'll soon have the opportunity to work with some seriously high voltage. I look forward to the training. While I can make some guesses, I'm sure not going to look to a general internet forum for lessons! Discharging capacitors and grounding lines are basic skills in some areas, and if someone hasn't already been taught, I have some trouble telling them anything more than: stay away!

Squirrel, you're not the only one here with lines qualifications, nor the first to have gone through engineer school. You can 'bare hand' HV? Impressive - but can you fly the helicopter too? At least one of the posters here can. So make nice.

End of sermon.

Last edited by renosteinke; 01/25/10 01:29 PM.
Joined: Jun 2007
Posts: 50
H
Member
A mad scientist answer to this problem:

The best option is to make the PoCo do it... its a dangerous operation that requires a specialized tool.

You would need a high voltage resistor (for safety, it MUST be rated for more than the expected voltage!) connected with high voltage cable to high voltage probes.

It could be built but beware, cut corners on the apparatus and DIE.

Building this is an exercise in engineering. You cant use just any HV resistor...it will be dissipating significant power and you don't want to burn it up. HV resistors cost $$$ and if it fries, it might arc over!

The whole thing would need to be potted in pure silicone for insulation.

Approximate calculations assuming a 200 watt resistor being fed 13.8kV... a 2Mohm resistor would do. (it would be well under its 200W rating at 13.8kV which is necessary considering its going to be potted)

What's scary is even if you build this thing and insulate it well AND you verify that the bank is at 0 volts....as soon as you take off this device, it may begin to partially recharge. The phenomenon is called dielectric absorption....charges in the dielectric migrate toward the plates and put some charge back on them! With a big cap, this residual charge could make you a crispy critter.

To prevent this, the caps must be shunted after discharging them.

Take all that in before tackling this. Safety issues aside; the tool could easily cost a few hundred dollars to make a safe one. HV probes, resistors and cables are expensive.

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