Can a ground fault through dirt trip the OCPD?

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hurk27

Senior Member
I appreciate the comments, Hurk. And something else dawned on me from reading your post.

I can see that some would have taken this thread to be a blanket statement from me that an OCPD could be tripped through earth anywhere on the planet. That was not my intention. I understand that everyone nowadays is taught that the earth /electrode sucks as a conductor at lower voltages. I think this is why some people got upset. My result went against the norm and the beliefs. What my test showed is that it isn't quite so cut and dried.

With the limitations of the written word on the net, as opposed to direct talk, my question was meant to be "Is there even a single case possible where a fault through dirt could trip a breaker at 120 volts?" I never ever believed or even implied that dirt/electrodes the world over could carry enough current to trip the OCPD. Before I even did the test, my belief was that most areas had soil with very high resistance. I also knew that my black clay soil was a pretty good conductor and I wanted to test it.

The whole thing started from that "grounding electrode question" thread when Iwire said that a ground fault through earth, under 600 volts, could never trip an OCPD.

So my experiment wasn't a blanket statement of proving that this would work anywhere. Essentially I was proving to myself that there is at least one place in the world where current through dirt tripped my OCPD.
Now I'm kind of getting at what your objective was, and as you said it wasn't too clear in the beginning, but as a whole I think the thread turned out to be a learning tool for a few members, I have lived in other parts of the country and I have had a few places where low resistance was very possible, like salt water areas around south Florida, and like your area most of Florida has a very high water table along with the fact it's also not very high above sea level, but working in many other areas has also enlightened me to the realities of these other places like here we have many areas that used to be the old shores of lake Michigan which are nothing but dry sand dunes grown over, as deep as you want to go, so with a perspective on both sides I understand the disbelief in some who have had a very hard time reaching a low impedance on a rod there whole career, but I like to share what I have learned over the years and even sometimes it gets miss-applied to a wrong thread, Grounding to earth is one of my better understandings in the electrical world, but I still keep an open mind, like I was always told the Earth as a whole had a resistance of .05 ohms, and it wasn't until I saw the papers on the 500kv DC SWER feed I think from Europe to another place where they were able to account for all the power loss in just the single conductor proving that the Earth in fact has an over all resistance of 0 ohms. so every day I still keep learning, and even some time re-learn things I have long forgotten you know the good ol CRS syndrome:D

But it is good brain exercise to discuss things like this if not for ourselves but for the many who are reading these threads.

When Bennie was around many times we would hook up in AOL and talk till the wee hours on this stuff, he would make you think out of the box.

Like I said I have done a few radio towers and have had to get the engineered specs of .5 ohms, not always easy but possible. Lightning and Earth grounding was one of my studies at university of Florida back in "78" as it was tied to getting my FCC 2nd class communication license, But much time has passed and I never went that route and let it go back, and more or less stayed with the electrical end.

Well I think I'm rambling, but Gary keep up the interest of doing the out of the box experiments, just keep it safe.:D
 
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.

I took a 10 foot piece of 1/2" rigid and cut in in half. I went to a spot outside the door to a grassy area. This is black clay soil in southest texas. The soil was moderately damp. Photo below:



I drove one of the 1/2" rigid pipes about 3 feet into the ground. The pipe is 5 feet long, notice 2 feet still sticking up. It went into the ground fairly easily, but I did use a sledge hammer to get'er in, but nothing difficult. Then I took a simpson meter on the Rx1 scale, zeroed it, and hooked it from the pipe to a brass water spigot on the side of the building.

Reading: 2 ohms approximately

The water piping in the building is steel. It goes up inside the brick wall to the rest of the plumbing - connected to the water main coming in on the other side of the building. I am guessing the city main is steel, and it runs in front of the building along the street.

Electrical service to building is 480Y/277. Inside there is a 208Y/120 xfmr. This xfmr has Xo bonded to the water pipe coming in the building. The point is, there is a whole lot of buried steel pipe acting as the grounding electrode.

So again, 2 ohms from the driven pipe THROUGH THE EARTH to the closest plumbing pipe in the area. Photo below:



Close-up of meter:



So I took a #8 copper wire to the pipe:



Connected it in the building to our experiment machine:



Here is the connection to the voltage source. The power source is fed through a subpanel from the 208Y/120 xfmr. It has a variable supply, I can go from 0 to 120 volts to neutral/ground. There is an OCPD in the power supply, it is supposed to be 15 amps but I suspect it trips a little sooner than that. I connected one phase of the supply through an ampmeter to the pipe via the #8.



As I slowly turned the voltage up to 50 volts, the current slowly went up to 6 amps. (these meters have not been calibrated in awhile, so I guess we may have a +/- 10% error here.



After playing around with these voltage/current levels a bit, I went ahead and cranked the voltage source up to 120 volts. The OCPD kicked out. Math says that if 50 volts gives 6 amps, 120 volts would be about 14 amps. Like I said, the meters are not calibrated, and the OCPD is not a normal breaker, it is more of a "reset" type button that kicks out when there is too much current.

Yeah, this is a fairly non-rigorous experiment, but a good amount of current certainly was flowing through the earth path.

Never say that 120 volts cannot trip an OCPD device through the earth. It can under proper circumstances.

Also, I did not "cheat" on any of this. No hidden wires, nothing like that. This is legit.

I would expect nothing else to happen.

I maintain this for a long time but the majority here is mislead by the general 'understanding' of grounding as it is propagated by the MHE.
 
I don?t understand why anyone is giving Gary a hard time on this thread. His test used a perfectly acceptable method to answer the question that it was intended to answer. This test is not about a normal installation. It is about the following question: Is it possible, or is it not possible, for a 120 volt source to trip a 15 amp circuit breaker, if planet Earth is part of the current path? The answer has been proven to be, ?yes, it is possible.? That is all that is being presented here.

This test has nothing to do with the NEC?s 25 ohm rule. There is no expectation that this test could be repeated in any other area of the country, using any other type of connection between power source and dirt, or using any other method of determining the resistance to ground of the electrodes, and having the test yield the same result.

Gary, I thank you for making the effort to perform the experiment and for reporting the results. :smile: You showed what I already knew to be true, and what anyone should expect to be true, if they but consider the question in its intended light.

Now, does anyone want to start a proposal for the 2014 NEC to allow dirt to become part of a recognized fault path for 120 volt systems? No? I suppose that is OK by me. I won?t offer such a proposal either. :wink:
Nor does his resistance measurement have ANYTHING to do with the measurement that would been the result of a fall-of-potential measurement. He did not measure the earth's resistance, he measured the resistance between the electrode and his probe at a certain distance.

Does anybody familar with the work of Tesla here? Most of his work would not make sense with the popular belief here. He proposed to use the EARTH as the conductor. Not just the ground, but the entire earth.
 
I wanted to revisit this. The original question was "could it ever be possible for a fault with dirt as part of the path to trip an OCPD?"

By definition, the building's electrode system is going to be included as part of the path. The building electrode is not "augmenting the path." it is absolutely part of the path.

Here is that path, starting at X1 of the 208Y/120 xfmr:

X1 to panel

panel to busduct via EMT feeder

busduct to busplug discoonect to subpanel in classroom

20 amp branch circuit to outlet

outlet to labvolt power supply

power supply through ammeter

ammeter to #8 wire laid on floor, out the door, to the driven pipe

driven pipe to building electrode system via dirt path

building electrode system to GEC

GEC to Xo of xfmr

So again, by design, the building electrode system is being used as part of the current path. The test is asking the question of "how much current can flow from a pipe driven in the ground to the building electrode system?"

I am positive that if I were to go out in the middle of the field next door and repeat the test, the current would be significantly lower. But that is not what the question asked.... which roughly was:

can Gary devise an experiment where significant current will flow through the earth from a 120 volt source?
What is the lineal distance from the fault point to the voltage source?
 

crossman gary

Senior Member
What is the lineal distance from the fault point to the voltage source?
From the 208Y/120 xfmr to the subpanel is about 50 feet of "relatively large" wire/busduct.

From the subpanel to my power supply is about 35 feet of #12 wire.

From my power supply out to the driven pipe is about 60 feet of #8 laying on the floor.

From the driven pipe to the city water main is about 40 feet. Driven pipe to the waterpipe coming into the building, about 70 feet. Driven pipe to the GEC and Xo, about 100 feet. Plus there may be other piping under the slab which is playing a role. So, distance to the building electrode is the unknown here.

For all I know, there may be some steel electrical conduits in the ground near my driven pipe. I just don't know. This building was built in 1967. I was only 7 years old...
 
From the 208Y/120 xfmr to the subpanel is about 50 feet of "relatively large" wire/busduct.

From the subpanel to my power supply is about 35 feet of #12 wire.

From my power supply out to the driven pipe is about 60 feet of #8 laying on the floor.

From the driven pipe to the city water main is about 40 feet. Driven pipe to the waterpipe coming into the building, about 70 feet. Driven pipe to the GEC and Xo, about 100 feet. Plus there may be other piping under the slab which is playing a role. So, distance to the building electrode is the unknown here.

For all I know, there may be some steel electrical conduits in the ground near my driven pipe. I just don't know. This building was built in 1967. I was only 7 years old...
Excellent!

So in your circuit you have a number of series resistance. Tr->panel->power supply->fault point(driven pipe)->Tr. completes the circuit. All portions of this with the exception of fault point->Tr are known sizes of conductors and known resistances. Since a fault traveling through earth have an infinite path of parallel resistances, you can only calculate the sum of the resistance, based on the known resistances, the voltage and current.

As you yourself identified the sources of variance of the undeterminable ground path, you identified the basic problem of using the earth return as a ground fault path return. One is the variance of earth resistivity and the other one is the distance. You may want to continue your expereiment and record your data with varying locations and same length and varying distances.

The fall-of potential will also give different results if the electrodes are driven in say an arbitrary 0 geographical degree(East) then moved 45 degrees(NE) and so on, because it is the earth resistance we are attempting to measure.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
I have done this experiment a few times with an 8' ground rod and the most current I found was a little over 5 amps and that was after a few days of rain. The other times it was two or three amps.
 

crossman gary

Senior Member
I must be sitting on the Mt. Everest of soil conductivity down here.

In my other experiment where I paralleled two pipes, if i extrapolate for 120 volts applied, it would have been 33 amps.

I wonder what it would have been with teo 8 foot ground rods?
 
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.
Have hose, will travel:D

I'm in Lake Jackson. I have no doubt about the validity of your findings, but if a doubting Thomas offers to show up, call me and I will come to support you.:smile:
 

crossman gary

Senior Member
Are you coming to Houston anytime soon? You would be more than welcome to stop by. We are on the south side of Houston near Hobby Airport. So not all that far from Lake Jackson.

Hey, you know that green brick telephone company building in Lake Jackson? I helped wire that back in 83 when I was a third year apprentice. It was a Southwestern Bell building back then, it is probably AT&T now?
 

hurk27

Senior Member
You know Gary a few years ago, when work was aplenty, and me wife less and hardly no bills, I traveled all over the country to the IAEI meetings, and then took three week vacations, I was in your area a couple times, I even drove my brand new work van to boot lol, I wish I knew ya then or I would have dropped in. I did have some post in here of my excursions. But now it would be hard, well maybe If I hit the Power Ball:grin:
 

crossman gary

Senior Member
Wayne, I would have enjoyed a visit from you.

Did you see my other thread with the results from the experiment I did this morning? The current flow was very high, especially for two pipes in parallel.

Now, surely there is someone on this forum from Houston? I surely would like someone else to confirm these results.
 

crossman gary

Senior Member
6400 miles is alot of driving, and with the Mickey Mouse Power line tower, now I have seen everything!

I get to do a bit of traveling in my job, but with my "on and off again" participation on this forum, I never thought to meet up with any other members.

Sometime ago I was registered as "crossman" on the forum. When I came back, I couldn't make any posts from the old account, so I started this new one.
 

hurk27

Senior Member
Yea in my single days I had allot of fun. met many people, and made a few friends.

I did dig up some info on earth grounding Here that might be of some help?
Has some good images of what I was talking about of the sphere of Influence, check the Figure links.

I'll try to find some more, Most of my work is on my old computer in a closet in my basement, maybe one day I'll dig it out and transfer it to this one.:wink:
 

hurk27

Senior Member
Wayne, I would have enjoyed a visit from you.

Did you see my other thread with the results from the experiment I did this morning? The current flow was very high, especially for two pipes in parallel.

Now, surely there is someone on this forum from Houston? I surely would like someone else to confirm these results.
I glanced at it, but didn't have time to post as I was on my way out, but I will check it out again;)
 
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