Ground tester or Hypot with 1/0 welding cable?

[Jim Stewart]

I have two devices that left me completely stumped. They are
Associated Research made devices. One seems to be a high voltage hypot
tester. Another has 1/0 welding cable attached to it. At least one is
called HyJoule.

I cannot conceive of why the hipot tester would
need anything bigger than say 12 gauge cable.
The unit should limit current to the milliampere
range.

I've never heard of a Hyjoule but now you have
me curious.

Anyway, I am lost as to just what could be tested with a 1/0 welding
cable (about 100 ft or so).

They are both the size of a under the desk refrigerator and VERY
heavy, maybe 200-300 lbs each.

Now I'm confused again. My hipot tester isn't
light, but is nowhere near that big. It's about
30 lbs in a 4U rackmount.

You might have some heavy duty mil-spec or
utility company stuff I've never heard of.
Probably not much demand for it on the civilian
market.

 

[Ignoramus30897]

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.

Paul, can you share some ideas about operating this thumper. such as
should I ground it to my house ground rod, and how can I test its
thumping function without spreading polonium everywhere or otherwise
getting myself or our electrical system in trouble. Obviously I would
not want to thump my house wiring.

i

 

[Paul Hovnanian P.E.]

You can find the location of a short in one of those realy big power cables
by laying it out and covering it with sand
then thumping it with a lot of current, the current cuases the cable to jump
and throw the sand up,
where the sand stops being thrown up is the location of the fualt.

Colin =^.^=

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.

 

[Ian Malcolm]

Paul, can you share some ideas about operating this thumper. such as
should I ground it to my house ground rod, and how can I test its
thumping function without spreading polonium everywhere or otherwise
getting myself or our electrical system in trouble. Obviously I would
not want to thump my house wiring.

i

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?

 

[ATP*]

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.

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.

 

[Paul Hovnanian P.E.]

Paul, can you share some ideas about operating this thumper. such as
should I ground it to my house ground rod, and how can I test its
thumping function without spreading polonium everywhere or otherwise
getting myself or our electrical system in trouble. Obviously I would
not want to thump my house wiring.

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.

 

[Paul Hovnanian P.E.]

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.

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.

 

[Ignoramus30897]

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.

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

 

[Ignoramus30897]

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

 

[Ignoramus30897]

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?

hoop can be seen here:

http://igor.chudov.com/projects/Water-Slide/waterslide2.jpg

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

i

 

[Paul Hovnanian P.E.]

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?

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.

 

[Paul Hovnanian P.E.]

[snip]

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.

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.

 

[Rich Grise]

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.

How's these?:
http://images.google.com/images?q=electrical+burns&btnG=Search+Images

Cheers!
Rich

 

[Ignoramus31595]

How's these?:
http://images.google.com/images?q=electrical+burns&btnG=Search+Images

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

 

[Rich Grise]

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 read an article in one of those "Popular this-n-that" magazines that
said you can use a copper pipe; solder a hose fitting on one end and
connect it to the hose. Turn the water on, and the water coming out
the end of the pipe will drill the way for the pipe. It should work
in clay; in the article it seemed that the copper pipe was a good
enough ground connection. (you turn off the hose and disconnect it,
of course. ;-) )

If you want to use the rod, see if your HD has a tool rental; if so,
you could probably rent something a little more suitable than an air
hammer to drive in a stick (like a post driver or something.)

Good Luck!
Rich