Ground tester or Hypot with 1/0 welding cable?

Ignoramus30170 · 2006-12-12T16:41:16+00:00

I have two devices that left me completely stumped. They areAssociated Research made devices. One seems to be a high voltage hypottester. Another has 1/0 welding cable attached to it. At least one iscalled HyJoule.Anyway, I am lost as to just what could be tested with a 1/0 weldingcable (about 100 ft or so). They are both the size of a under the desk refrigerator and VERYheavy, maybe 200-300 lbs each. i

P

Paul Hovnanian P.E. 19 years ago

They use these things for locating faults in buried cables. It is not necessary to lay out the cable and cover it with anything (assuming an unburied cable) because the arc at the fault location will sound like a rifle shot (or worse).

Back when I used to run one of these for the local power company, the standard method for locating the fault was to start up the thumper, which has about a 5 second cycle, and start walking slowly along the route of the cable. The 'thump' can be felt faintly through your feet or heard by using a piece of conduit as a stethoscope. This will work for cables that are up to several thousand feet in length.

One of our linemen always brought his dog to work with him in the truck. The dog had been on so many underground repair jobs that, as soon as the thumper was started, he would take off running to the fault location and bark at it when he arrived. That saved us quite a bit of time.

Vote

I

Ian Malcolm 19 years ago

It obviously puts out a fairly substantial current pulse. Why would you risk connecting it to your house ground rod? If it requires a ground, why not drive a ground rod away from your house and any buried utilities?

Vote

A

ATP* 19 years ago

Sounds like that dog was taking "unit work"! Buried in sand we never had much of a problem, but deep under pavement could be a bitch, or if the line was adjacent to a steel pipe. Once they start to fault you better plan on replacing that primary in a timely fashion.

Vote

G

Gerald Miller 19 years ago

Donate it to werty Gerry :-)} London, Canada

Vote

P

Paul Hovnanian P.E. 19 years ago

First of all, we never operated our thumper without lineman's insulating gloves.

I'd suggest that you don't fiddle with it at all. But if you must, drive a separate ground rod, away from your house. There should be a grounding lug on the thumper. Connect that to your ground rod with a #4 stranded Cu conductor.

Make a spark gap out of two pointed metal rods, spaced about 1/8" apart mounted on some suitable insulating material. Connect one side of this gap to the thumper HV lead. Connect the other side of the gap back to the thumper grounding lug with its own lead (not the one to the ground rod). Turn the thumper's voltage control to minimum. Put on your lineman's gloves, Plug the thumper's 120VAC cord into an isolated source, such as a portable generator. Turn the thumper on and very slowly* increase the voltage setting until the gap starts to flash over.

*Don't be impatient. The contactor in the thumper connects the internal cap. to the output only periodically, so if you crank it up fast, it won't discharge until the contactor closes anyway.

Vote

P

Paul Hovnanian P.E. 19 years ago

I could never tell if the dog heard the thump, felt it through his feet, or could smell the arc products.

In New York City (IIRC), they had a problem with locating leaks in oil filled HV cables under city streets. They experimented with gas detectors, injecting chemical or radioactive tracers and all sorts of other gadgets with limited sucess. Then someone had a dog trained to pick up the scent of the insulating oil. Problem solved.

Vote

I

Ignoramus30897 19 years ago

Paul, thank you. I unloaded it, connected the two parts (ground, HV, and control cable) and experimented a little bit.

All the while I controlled it with a wooden board, never touched it with my hands while it was on.

It powers up.

It does not show any DC voltage on the meter.

There is a tiny popup breaker in the back of the power supply. When I tried to depress it (using that wooden board), the GFCI interrupted electricity. I decided to wait for a drier day when I can run it off my generator and can see everything in daylight etc.

i

Vote

I

Ignoramus30897 19 years ago

Paul, a grounding question. I have a basketball hoop in my yard that is held by a 4x4 steel square tubing (really big square tubing). It was installed by previous owners. I suppose that it is held in the ground by concrete poured around the 4x4 steel tubing.

Can I use that as a ground for the thumper?

i

Vote

I

Ignoramus30897 19 years ago

hoop can be seen here:

formatting link

it is in the back behind the pool, between the pot with olive tree and towel hung out to dry.

i

Vote

L

Larry Jaques 19 years ago

On Thu, 14 Dec 2006 04:16:47 +0000 (UTC), with neither quill nor qualm, Ignoramus30897 quickly quoth:

That's a Hula Hoop, bubba. Hey, what's with all the headless kids?

Vote

I

Ignoramus31595 19 years ago

I wanted to "protect privacy"...

i

Vote

P

Paul Hovnanian P.E. 19 years ago

No. Drive a new ground rod. There's no telling how poor the conductivity of a lump of concrete might be. This is a life safety issue.

Vote

P

Paul Hovnanian P.E. 19 years ago

[snip]

There is some sort of fault between the input and ground. Don't use this thing until you have repaired it.

If the fault is in the HV transformer, you might have a situation where the HV will get back into the 120V side. That's the reason for using a stand alone generator (to keep from killing people in your or your neighbor's house). With a generator feeding this beast, odds are only you will die.

I used to have links to some nice(?) photos of HV electrical burns, but I've misplaced them. Perhaps someone else can post them in this thread.

Vote

I

Ignoramus31595 19 years ago

Scary stuff. I bought a ground rod at Home depot today. it is 10 feet long. should I use all 10 feet oor can I get away with a shorter rod? my soil is clay.

Also, has anyone tried using an air hammer to beat in the ground rod.

i

Vote