# WTH is a thumper. For underground faults.



## Bbsound (Dec 16, 2011)

Bossman wants me to do some research on "thumpers".
He saw our power utility use one to locate an underground fault in direct burial. 
What are they? How does it work? What would be a good one to purchase? 

I have used the meter stuck into the earth method before succesfully, so I understand that part of it.


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## wildleg (Apr 12, 2009)

it's a meggar, only more dangerous.


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## brian john (Mar 11, 2007)

A thumper pulses the line with a high voltage, and at the location of the weak spot in the line makes a loud noise (from the fault) this is traced with a noise sensoring set.

This would be destructive to 600 VAC wiring.


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## MDShunk (Jan 7, 2007)

I own one, but I don't have any sensoring equipment. I just walk the area a feel for the strongest thud in the soles of my boots. Accurate to within a size 10.


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## NacBooster29 (Oct 25, 2010)

We have a fancy one. It gives the depth of the cable. It can locate pipes also. Very useful. But pricey. I believe the boss paid >5 grand. I don't remember what brand.


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## MDShunk (Jan 7, 2007)

I seriously doubt you're using a thumper to locate pipes.


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## al_smelter (Jan 25, 2011)

We have a nice thumper here at work and it has come in quite handy at times. Our high voltage cable (15kV) is installed in very long runs in underground conduit, and is routed through multiple manholes (six separate feeders in the plant). When we have a failure, I open all the manholes in that run, station people at each, and thump the cable. I have found failures inside the manhole (a simple splice fix), and can find which run of conduit the failure has occurred (a possible partial pull). The sound is quite sharp, almost like a gunshot. Easy to find the failure in pipe. I am not familiar with direct burial use.

However, you surly don't want to use a thumper unless you are SURE there is a fault and are prepared to fix it. It is a highly destructive test and will almost certainly ruin the cable you thump.

Edit- How would a thumper locate a pipe or give depth?


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## socalelect (Nov 14, 2011)

MDShunk said:


> I own one, but I don't have any sensoring equipment. I just walk the area a feel for the strongest thud in the soles of my boots. Accurate to within a size 10.


Marc,
What's the voltage out. Put of a thumper?


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## Zog (Apr 15, 2009)




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## NacBooster29 (Oct 25, 2010)

http://www.radiodetection.com/products_det.asp?art_id=6375&sec_id=2689


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## MDShunk (Jan 7, 2007)

NacBooster29 said:


> http://www.radiodetection.com/products_det.asp?art_id=6375&sec_id=2689


Lol. That's an ordinary pipe and cable locator. A thumper is a rather large tool on dolly wheels.


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## kbsparky (Sep 20, 2007)

We use a "Spit-fire" type unit to locate faults in low-voltage (under 600V) underground cables.

It sends out a pulse every few seconds which you can detect with 2 probes and a meter to trace out the underground fault.

I can locate the bad spot in a buried cable to within a couple of inches from the surface of the ground using such equipment. 

This is not the same as the high-power thumpers used on high-voltage primary lines.


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## NacBooster29 (Oct 25, 2010)

Hey you learn something new everyday. The guy who showed me how to use this one, hooked the signal emitter to the ends of a faulty if cable. And we followed it until the signal went way down. Found the fault. I kind of assumed that was the same device.


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## macmikeman (Jan 23, 2007)

I wonder if what the op is really referring to is the use of a "beast" device. 

It isn't a commonly used tool outside of power companies usage, because it will impose voltage and current into the primary side all the way back to the utility transformer and they do not necessarily like "peabody electric and appliance repairs " to be attempting such. 

They are however terrific at determining if the poco side of the disconnect is where the neutral connection is loose or failed.


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## socalelect (Nov 14, 2011)

macmikeman said:


> I wonder if what the op is really referring to is the use of a "beast" device.
> 
> It isn't a commonly used tool outside of power companies usage, because it will impose voltage and current into the primary side all the way back to the utility transformer and they do not necessarily like "peabody electric and appliance repairs " to be attempting such.
> 
> They are however terrific at determining if the poco side of the disconnect is where the neutral connection is loose or failed.


What is the thumper voltage output?


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## JRaef (Mar 23, 2009)

A common fault locator for LV cable is a TDR, Time Domain Reflectometer. It sends a pulse down the line and times the reflection, which happens if there is a "leak" in the insulation. Then it times the reflected pulse and calculates the linear distance from where the TDR is connected.


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## macmikeman (Jan 23, 2007)

socalelect said:


> What is the thumper voltage output?


Atually I got that injects voltage part wrong. It does current in adjustable increments. Here is a link. http://www.arnettindustries.com/pdf/mega-beast-brochure.pdf


They also make an instrument for detecting faults or breaks in buried cables as well. Scroll down the page for that.


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## al_smelter (Jan 25, 2011)

Turns out that our thumper does have TDR capability. I have never used it because it's fairly simple to locate our MV faults in the conduits. I suspect that I will probably use it now just for shilts and giggles to further my never ending education in this field.


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## Bbsound (Dec 16, 2011)

kbsparky said:


> We use a "Spit-fire" type unit to locate faults in low-voltage (under 600V) underground cables.
> 
> It sends out a pulse every few seconds which you can detect with 2 probes and a meter to trace out the underground fault.
> 
> ...


This is exactly what was described to me. 

Found it, thanks


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## Bbsound (Dec 16, 2011)

macmikeman said:


> I wonder if what the op is really referring to is the use of a "beast" device.
> 
> It isn't a commonly used tool outside of power companies usage, because it will impose voltage and current into the primary side all the way back to the utility transformer and they do not necessarily like "peabody electric and appliance repairs " to be attempting such.
> 
> They are however terrific at determining if the poco side of the disconnect is where the neutral connection is loose or failed.


I think you are right mac, I think what kbsparky is talking about is what we are looking for


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## MDShunk (Jan 7, 2007)

macmikeman said:


> I wonder if what the op is really referring to is the use of a "beast" device.
> 
> It isn't a commonly used tool outside of power companies usage, because it will impose voltage and current into the primary side all the way back to the utility transformer and they do not necessarily like "peabody electric and appliance repairs " to be attempting such.
> 
> They are however terrific at determining if the poco side of the disconnect is where the neutral connection is loose or failed.


I own a beast of burden also, and it does not act as you describe at all. It's just a load bank in a handy package. It is used to find marginal or open neutrals and hots.


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## MDShunk (Jan 7, 2007)

socalelect said:


> What is the thumper voltage output?


Mine has a switch for 15kv and 30kv (which is more like 14 and 28 on my set).


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## socalelect (Nov 14, 2011)

MDShunk said:


> Mine has a switch for 15kv and 30kv (which is more like 14 and 28 on my set).


Holy crap that's a **** load


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## MDShunk (Jan 7, 2007)

socalelect said:


> Holy crap that's a **** load


I think modern ones are adjustable from naught to whatever, but mine just has a switch. It's at least 30-35 years old. Just waiting on the caps to go kaboom one of these days. It was rough when I bought it 15 years or so ago.


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## acro (May 3, 2011)

al_smelter said:


> We have a nice thumper here at work and it has come in quite handy at times. Our high voltage cable (15kV) is installed in very long runs in underground conduit, and is routed through multiple manholes (six separate feeders in the plant). When we have a failure, I open all the manholes in that run, station people at each, and thump the cable. I have found failures inside the manhole (a simple splice fix), and can find which run of conduit the failure has occurred (a possible partial pull). The sound is quite sharp, almost like a gunshot. Easy to find the failure in pipe. I am not familiar with direct burial use.
> 
> However, you surly don't want to use a thumper unless you are SURE there is a fault and are prepared to fix it. It is a highly destructive test and will almost certainly ruin the cable you thump.


Why is this considered a destructive test? From my understanding(which is limited), during the test it likely makes an actual fault worse but allows you to pinpoint the location.

But would it actually harm an undamaged cable?




brian john said:


> A thumper pulses the line with a high voltage, and at the location of the weak spot in the line makes a loud noise (from the fault) this is traced with a noise sensoring set.
> 
> This would be destructive to 600 VAC wiring.


If so, what's the point in locating it? The cable would have to be replaced anyway.


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## oldtimer (Jun 10, 2010)

acro said:


> Why is this considered a destructive test? From my understanding(which is limited), during the test it likely makes an actual fault worse but allows you to pinpoint the location.
> 
> But would it actually harm an undamaged cable?
> 
> ...


 


When I worked at an iron ore mine , we used to check the trailing cables with a Hi Pot tester. I believe this is what you refer to as a thumper . 
This would locate the damaged area of the cable , which was then sliced open , repaired , and then re- vulcanised.

Then the cable would be re-used when needed.

Of course there was a limited number of splices that could be made , and when that limit was reached the cable was sent to the boneyard.

These cables were used on 4160 volts.


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## JohnR (Apr 12, 2010)

Here is what a thumper is.


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## 360max (Jun 10, 2011)

MDShunk said:


> I own one, but I don't have any sensoring equipment. I just walk the area a feel for the strongest thud in the soles of my boots. Accurate to within a size 10.


walk barefoot, accurate within 1/16 of :laughing:an inch


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## Big John (May 23, 2010)

acro said:


> Why is this considered a destructive test? From my understanding(which is limited), during the test it likely makes an actual fault worse but allows you to pinpoint the location.
> 
> But would it actually harm an undamaged cable...?


 Depends on the cable. I've never seen or heard of anyone thumping low-voltage cables.

A 5kV or 15kV cable can be impulse tested because you don't necessarily need to apply voltage greater than the insulation can handle to locate the fault.

On a 600V cable, you most likely wouldn't be able to locate any faults at 1000V, and if you increase beyond that point you risk causing further insulation damage. This is also very true for old medium voltage cable: Even though brand new it may withstand several times the nominal insulation rating, once it's aged in service you run the risk of causing it to fail by exceeding that.

-John


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## Service Call (Jul 9, 2011)

They've used thumpers here to locate a problem under the river. Divers would swim the length of the cable waiting for the "thump". I know one diver who broke a tooth doing that.


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## nrp3 (Jan 24, 2009)

I have used the Timco and it works. I have the Aquatronics model of that, the greenlee A frame one, and the A frame that goes with my Dynatel locator. Something like this is likely what you are looking for. Great for UF and URD.


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## Zog (Apr 15, 2009)

Nice video I found today on thumpers

http://blog.protecequip.com/blog/co...FWoEnZ9mMBAQZC81gyR5PG/mGf49N9+BTAkKzTDLwjg==


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