Can a ground fault through dirt trip the OCPD?

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crossman gary

Senior Member
Bob,

Houston is about 30 feet above sea level, right on the Gulf coast. We have high humidity and typically get a lot of rain which keeps soil conditions moist.

I have no idea of the chemistry of the "black gumbo clay" soil we have, but I have been aware of its conductive characteristics for some time. And, the wetter it is, the more conductive it is. I would bet that it has to do with the amount of minerals and salts in the soil which become ionized when dissolved in water.

Scientists say that this area was at one time completely under the ocean. I am sure this has something to do with our conductive soil. Calcium salts, other mineral salts, regular salt, all of this stuff ionizes when in water, and these ions help carry current.

Now, for the past 2 weeks, we have had a drought down here, so the soil has been pretty dry. Last night though, we finally got a pretty good rain, so the soil was moderately moist. This is what prompted me to do the test this morning rather than last week. I definitely chose conditions which were conducive to conductivity. If I did this test last week when it was very dry, I am certain the results would have been different. Also, the rigid pipe was brand new, meaning no rust or corrosion on the galvanized exterior. Right after I drove the pipe in, 3 feet deep, I took the ohm reading to the spigot. It read 2 ohms.

Like I mentioned before, this reading of 2 ohms from the pipe to the water spigot has a ton of parallel paths. It is going to the water main in the street which as I mentioned is miles and miles long underground. It is going to the water pipe coming into the building which is about 120 feet long and buried. It may be going to the 20,000 square foot slab and rebar system/building steel.

This is definitely NOT a test of ONLY the driven pipe like a three point ground test is done. I am not claiming it is.

Obviously all this could be faked in my pictures. I have no reason to do so.

I totally believe that other areas of the country have really poor conductive soils. I am certain that some places it would be difficult to get below 100 ohms. I believe what you guys are saying about other areas. But down here, this experiment isn't lying.

Hey, 2 weeks from now, maybe the conditions are completely different. Maybe it rains alot and even MORE current would flow. Maybe it doesn't rain, and the current is way less.

Right now, 50 volts pushed 6 amps through it.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
Gary I apologize if I came off as giving you a hard time. That was not my intent and you obviously have more equipment and know how then I do in this situation. I must admit I was thinking maybe something was amiss with the ground rod ohms being that low. I learned something. I believe someone in Iraq said that the soil conditions there were incredible conductive also.

It sort of makes me think about all the stray currents flowing thru the ground down there-- Is that why everything grows big in Texas? :grin:
 

crossman gary

Senior Member
No worries Dennis. I did not take your comments as being derogatory.

But I do need to make one correction.... If anyone takes me up on the offer of paying their air fare if the experiment isn't repeatable... well, >>>I<<< get to chose the day we do the experiment!:smile:

The reason is, if you show up on a day when it hasn't rained in a few weeks, I am going to lose. So I am putting a stipulation on this that the soil must be WET.
 

Rick Christopherson

Senior Member
I am not saying Gary faked anything but something is odd here. :smile:
The only thing that I find odd is the number of people here that don't realize how significant the differences are between soil conditions. Soil conductivity is going to change from lot-to-lot, let alone from state-to-state. Even if you drive a rod into an isolated highly conductive pocket of good soil that is surrounded by poor soil, you have effectively increased the size of your rod by the area of the good soil.

The Earth is not homogeneous, and contrary to what I think I heard Mike Holt suggest in one of his videos, nor is it equipotential.
 

crossman gary

Senior Member
Okay, I did the following experiment which was initiated from the "grounding electrode conductor question" thread. The point was to determine if a fault path through earth could trip an OCPD.
Maybe the way I stated my question is what got everyone upset.

Perhaps this would be better:

>>Realizing that many areas of the country have soils with poor conductivity, and that in these areas it is virtually impossible to trip a 15 amp breaker by connecting a 120 volt phase wire to a rod or pipe driven into the earth, I am seeking to determine if a portion of my soil could possibly have a low enough resistance to carry significant current, or to even possibly trip a 15 amp OCPD, under the experimental conditions which I propose, conditions which I acknowledge are not normal conditions under which ground faults would be subjected to.<<

Is that better for everyone??

:wink:
 
Gary
Move your 5ft ground rod further from the building and see if you get the same result. Stay away from the location where the water pipe enters the building.
(I believe your experiment setup is too close to the buildings existing electrode system, which is "augmenting" the current path.
 

iwire

Moderator
Staff member
Location
Massachusetts
The only thing that I find odd is the number of people here that don't realize how significant the differences are between soil conditions. Soil conductivity is going to change from lot-to-lot, let alone from state-to-state. Even if you drive a rod into an isolated highly conductive pocket of good soil that is surrounded by poor soil, you have effectively increased the size of your rod by the area of the good soil.

The Earth is not homogeneous, and contrary to what I think I heard Mike Holt suggest in one of his videos, nor is it equipotential.

Rick, no need to try top put words in anyones mouth. No one has said the earth is homogeneous, but 6 ohms in natural soil conditions is in an unusually low reading for just 3' of rod.

Look through the posts here going back to 2002 and I doubt you will find a similar post.

Again I am in no way suggestion Gary faked or rigged anything.

I just think there is something unaccounted for here.
 

crossman gary

Senior Member
Pierre:

Here is a diagram of the building. The building is shown in tan, gray is parking lots, green is grass. The underground waterpipe is located on the other side of the building from where I did the experiment. The actual location of the GEC connection is about 100 feet away. The water main at the street is about 40 feet away. The place where I drove the road was about 3 feet from the foundation.

The brass water spigot in the brick wall is not really part of the electrode system. The pipe to that spigot goes up the inside wall into the attic. Then it runs all the way across the building to the place where the city water enters the building. Like I said, that piping is most likely not contributing in this case since it isn't in direct contact with the earth in the vicinity of the pipe I drove into the ground.

I could redo this experiment by moving closer to the street. In that case, I am moving closer to the city main, and that may make the current even higher. I would have to see.

I am guessing that the building has some pretty deep concrete footings too. So, on the electrode side, I believe there is a real good conductivity to the earth: Lots and lots of city waterpiping which is steel. Lots of square feet of slab with deep footings and rebar and an all-metal building frame.

 
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crossman gary

Senior Member
A real soild resistivity test would prove or disprove this theory.
That doesn't make sense to me. All I am relaying to the rest of you is the results of my experiment.

And the question was basically "Could there ever be a condition where earth could carry a significant current?"

The question was not an inquiry about driven rods way out in the middle of nowhere and its resistance to earth.

The pipe was 3 feet from the slab, and 100 feet from the GEC connection, and 40 feet from the street water main. Those were the conditions I chose, and the current was what I am saying.

So yes, there are conditions at my building in which a portion of earth can carry significant current.
 

crossman gary

Senior Member
Do any of you guys know anyone in the Houston area? If you can hook them up with me, I would be happy for them to come out and see for themselves, then they could relay the findings to the rest of you. PM me for address and details.

I would be happy to oblige. And as I said before, to repeat the results, the soil needs to be at least as wet as it was today.... that isn't too hard, it generally is pretty wet, unless we are in a drought.
 

hurk27

Senior Member
I have done this very experiment, using a 25 volt source, I think I came up with 1.4 amps which showed I had about 18 ohms resistance on the rod to the water pipe I was using as the other part of the circuit.

If the analyzing results are correct from the 500kv DC SWER feed from Europe to what I think was Iceland, it was calculated that at DC the earth as a whole has 0 resistance, this was calculated by accounting for all the lost energy which was accounted for in the single conductor from the supply to the load with no loss in the Earth return.
It is our connection point to earth that is the weakest link.
The area around an electrode has the highest resistance because of the fact it has the smallest area of soil in proximity with the rod. This is called the "sphere of influence" It is this connection point we have to deal with, I have done many radio towers and I have seen many methods to get resistance down to .5 ohms, but it takes allot of engineering to do this in most common soils.
Using the 3 point fall of potential is just one method to finding the resistance of a electrode system, as voltage injection is another, there are some clamp on testers that do this very same thing (why do you think they are clamp on).
So applying a voltage (hopefully a safe voltage) to an electrode and measuring the current can be a good indication of the resistance of the electrode to the common electrical system grounding which is what we want any ways as long as our source voltage is also common to the electrical system grounding.
 

quogueelectric

Senior Member
Location
new york
I totally applaud you for setting up an experiment this elaborate. You shouldnt have to explain yourself to the lazy schmucks who never took a step out of thier way to prove anything. More power to you . Dont feel you owe everyone an explanation for your work.
 
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crossman gary

Senior Member
I have done this very experiment, using a 25 volt source, I think I came up with 1.4 amps which showed I had about 18 ohms resistance on the rod to the water pipe I was using as the other part of the circuit.
Thanks for that info, Hurk27. Looks like my current was about double what yours was, but at least your experiment and mine are in the same ballpark.

What area of the country?
 

crossman gary

Senior Member
I totally applaud you for setting up an experiment this elaborate.
Thank you. I can really get into this kind of stuff sometimes.

You shouldnt have to explain yourself to the <those> who never took a step out of thier way to prove anything. More power to you . Dont feel you owe everyone an explanation for your work.
Again, thanks! To be honest, the discussion is 3/4 of the fun for me. I hope that everyone including myself learns from it here on the forum. I enjoy the educational back and forth nature of the discussion. I do not mind the opposing views. I am generally a skeptical person myself, so I do not begrudge anyone questioning my results. If I was on the other end, I would probably be "prove it!"

The only thing I would ask for is an honest attempt from everyone to understand what is going on, not just disbelieve with no effort to seek further knowledge.

Some have questioned that maybe there is something unseen going on. Could be. I know there are some rigid conduits which leave the building out to the light poles. I think they come form the back of the building though, but who knows? Maybe there are some metal pipes connected to the electrical panels right in the ground near where I drove the pipe. -- I don't think the pipes are there because of what is inside the building, but I cannot say with 100% certainty that there isn't anything buried where the "rod" was.

I will most likely play with this some more, driving the rod in various areas, various depths, and see what I find.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Gary, I'd like to know what the voltage setting needs to be to flow 15a, which should not trip the breaker.
 

crossman gary

Senior Member
Larry:

The labvolt power supply I used doesn't have a "breaker", it has a "reset" type button which I suppose is somewhat akin to a klixon switch. In my original post, I acknowedged that this OCPD may trip at less than 15 amps.

I agree that a regular 15 amp breaker is not going to trip immediately, if ever, at 15 amps.

Here was my mindset when I did the experiment: I definitely don't want to burn anything up, I don't want to ruin the expensive 3 phase variable supply. I am not really wanting to send amperage indescriminantly through the waterpipes, the electrodes, or anything else in the building.

So I start at 0 volts. I slowly turn up the voltage to 50. The current comes up to 6. I go back down to 0 volts, and repeat this a few times. I am still concerned about where that 6 amps is going.... I am thinking.... "what if someone is in the bathroom and the faucet shocks the crap out of them?"

I realize this shouldn't happen, but you never know.

So I did all the volts/amps part of this pretty quickly. The ammeter I was using only went to 8 amps. There was another ammeter with a 25 amp scale, but I didn't have it connected. So, all of a sudden I got brave and without thinking, I cranked the supply to 120v. The reset button popped out and the voltage was gone.

I don't know what the current was at 120v. I can do the math and it comes out to a bit over 14 amps.

I could go back and use the 25 amp meter and see what it takes to trip the reset. Most likely these experiments aren't over. I'll do more if anyone is interested. I'll try the pipe in various places, different lengths.
 
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